Captain<br />Member # 3929<br /><br />posted March 11, 2003 12:30 PM Profile for SCO Edit/Delete Post I <br /><br />have been plagued by poor idle start problems with this engine.<br /><br />It runs great everywhere else, and I thought with some running time it might <br /><br />begin to idle better. rpms are 700 at idle immersed, and 1000 on the muffs. I <br /><br />have triple checked spark, with a spark tester and get good, regular, strong <br /><br />7/16(edited, I tested for 7/16, not 5/8) jump.<br />compression is 120 plus all around, with little deviation.<br /><br />Takes too long to start, and multiple tries even after the choke has pulled <br /><br />fuel to the engine. Once it starts and runs a while it idles ok on muffs and in <br /><br />the water, but will sometimes die when putting it into gear. It is much harder <br /><br />to start in the water. I am alweys envious of the idle and start of other 2 <br /><br />strokes and sometimes wonder if the newer ones just start and idle better <br /><br />inherently, and that maybe in '73 they hadn't figured out how to make the <br /><br />engine idle properly yet.<br /><br />This weekend for example I had run at 3700 for some 15 minutes, then idled into <br /><br />the boat ramp area for some 5 minutes, and when powering onto the trailer it <br /><br />bogged and died. Restarting and running at some 2500 or so for a few seconds <br /><br />allowed me to power up to near wot with no bog. I cant tell if it is fuel <br /><br />starved or loading up with too much fuel at idle.<br /><br />Joe, if you are reading, you gave me the idle jet info for this engine, that <br /><br />some were too small, and can be drilled just to size(.031 inch diameter), or <br /><br />they could be clogged some). I will check for this. Could these symptoms be <br /><br />caused by misfitting reeds or leaky choke butterfly flapper? Is there a way to <br /><br />check idle suction or airflow. If internal seals are leaky I guess the problem <br /><br />is very difficult to correct requiring overhaul.<br /><br />The plan:<br />1) carb kits and immerse carbs overnight in a cleaner. Drill idle jets if <br /><br />necessary. Any recommendations for a cleaner?<br /><br />2) rework butterfly linkages and carefully check fit.<br /><br />3) Replace reeds.<br /><br />Sorry for the long post. Resummary of questions:<br /><br />Is the motor loading up with too much fuel at idle, or starving in your <br /><br />opinion('s).<br /><br />Do these '73 v4s inherently start and idle poorly?<br /><br />Are reeds/ internal seals a likely culprit for poor idle/start?<br /><br />Is there a way to check idle suction or airflow? Posts: 602 | Registered: Aug <br /><br />2001 | IP: Logged<br />Joe Reeves<br />OMC Guru<br />Member # 6826<br /><br />posted March 11, 2003 01:28 PM Profile for Joe Reeves Edit/Delete <br /><br />Post SCO.... In reply to your questions:<br /><br />1) Dismantle the carbs completely before immersing in carb cleaner. Be sure to <br /><br />remove any nylon/plastic components. Use regular automotive carb cleaner which <br /><br />is usually available in a one gallon container, equipped with a small basket.<br /><br />2) Rework the butterfly linkages via the external linkage rod setup so that <br /><br />they open and close at the same time.<br /><br />3) I would not replace any of the reeds unless they were broken.<br /><br />4) You can easily check whether the engine is starving by simply having it <br /><br />running with the carburetor face plate off, then one throat at a time, stick <br /><br />two (2) fingers in the carb throat. If the engine slows down, consider the <br /><br />mixture okay. If the engine rpms increase, consider that cylinder running lean <br /><br />(starving).<br /><br />4a) With the engine not running, pump the fuel primer bulb. If fuel flows out <br /><br />any of the carb throats, it would be loading up. It would also load up if <br /><br />someone installed the wrong jets in the carburetors in some vain attempt to <br /><br />increase horsepower.<br /><br />5) The 1973 V/4 engines only start and idle poorly if something is wrong. <br /><br />They're a good design and normally start and run just fine.<br /><br />6) Reeds/internal seals are not a likely culprit for a poor idle/start <br /><br />condition. That would be quite unusual.<br /><br />7) Sticking your fingers in the carburetor throats as mention above would be a <br /><br />fairly good indicator of checking the idle suction or airflow?<br /><br />If that engine has compression in the range of 100+ psi and even on all <br /><br />cylinders, has spark (w/plugs removed) that will jump a 7/16" gap with a strong <br /><br />blue flame on all cylinders, the carburetor passageways are clear and proper, <br /><br />and the choke operates as it should, it should start within four or 5 <br /><br />revolutions.<br /><br />I'm assuming that you pump the fuel primer bulb up hard first, and that you do <br /><br />increase the throttle setting before attempting to start the engine (not <br /><br />attempting to start at a dead idle). Let us know what you find.<br /><br />--------------------<br />Joe (30+ Years With OMC)<br />Posts: 791 | From: Central West Florida | Registered: Feb 2002 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 11, 2003 01:53 PM Profile for SCO Edit/Delete Post <br /><br />Thanks Joe. I will do all this weekend if I can get the carb kits. Right now, <br /><br />when cold on the muffs, at best it takes a full 6 to 8 seconds of full choke <br /><br />good battery cranking before it shows any life then takes another 3 to 5 <br /><br />seconds to catch. I always pump up the bulb, and it doesn't leak out the carbs. <br /><br />Since it should start in 4-5 revs or so and only sputters slowly to life, I'm <br /><br />now suspecting starvation/jet clog/insufficient diameter. I'll do the finger <br /><br />tests, recheck compressions and spark, check jet sizes, inspect reeds, rebuild <br /><br />carbs, test and report back. Thanks again. Posts: 602 | Registered: Aug 2001 | <br /><br /> IP: Logged<br />Dhadley<br />Admiral<br />Member # 685<br /><br />posted March 11, 2003 05:20 PM Profile for Dhadley Edit/Delete <br /><br />Post The 73 135's did idle funny. We used to put 115 heads on them and it <br /><br />seemed to help a lot. The sensor air gap was critical too.<br /><br />Keep us informed after you get the carbs cleaned.<br /><br />Good luck! Posts: 2116 | From: Port Charlotte FL | Registered: Feb 2001 | IP: <br /><br />Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 11, 2003 05:23 PM Profile for SCO Edit/Delete Post <br /><br />what sensor, the flywheel magnet sensor(s)? Posts: 602 | Registered: Aug 2001 <br /><br />| IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 16, 2003 09:26 PM Profile for SCO Edit/Delete Post <br /><br />Update. I pulled the carbs today, and they were clean. I had a wire gage <br /><br />tester, and found a copper wire that fit into the .035 hole with a fair amount <br /><br />of slop so was clearly less than .031 diameter. This wire was larger than any <br /><br />of the 4 idle jets. I couldnt find a drill that size anywhere, so I have to <br /><br />leave it. I also was afraid to unscrew the jet without the omc tool for that <br /><br />purpose. What do you all recommend, getting the omc jet unscrew tool and 4 new <br /><br />jets(what diameter), or just drill them out to .031? Is .031 the ideal diameter <br /><br />or is there a jet I should buy? Posts: 602 | Registered: Aug 2001 | IP: <br /><br />Logged<br />JohnM<br />Captain<br />Member # 18044<br /><br />posted March 16, 2003 11:33 PM Profile for JohnM Edit/Delete Post <br /><br />Hi SCO,<br /><br />I too have a similar problem, but my motor is a 55HP 79 Envinrude. Engine is <br /><br />fine until it warms up and then sits for 10 minutes. I have tried a lot of <br /><br />things with the help of this forum. Unfortunatley though, I still have the <br /><br />problem but have learnt heaps in the process for which I am grateful. You may <br /><br />want to do a search for "JohnM" or "Carbs didn't look dirty. Is this normal". <br /><br />There is a plethora of info that may solve your problem in this thread.<br /><br />I have ordered new carb kits(again) and new jets for my carbs. I am hoping this <br /><br />fixes the problems I am having.<br /><br />--------------------<br />JohnM AKA...The Proffesional Amateur!<br />Posts: 52 | Registered: Dec 2002 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 26, 2003 12:41 PM Profile for SCO Edit/Delete Post <br /><br />Update: I checked with the local dealer and found the recommended jet size is <br /><br />.030, but not to contradict Joe, there is no american drill size at .030. Drill <br /><br />sizes go from .292 to .031. I purchased these 2 drills and found that the jets <br /><br />are just larger than .292, and probably the omc part diameter of .030. I'm <br /><br />thinking the jet sizes are ok, but I ordered new jets, and will drill the <br /><br />existing ones to .031 to test. Posts: 602 | Registered: Aug 2001 | IP: Logged<br />Nscarpi<br />First Mate<br />Member # 20576<br /><br />posted March 26, 2003 05:49 PM Profile for Nscarpi Edit/Delete <br /><br />Post Hello SCO: I removed the heads from my 115. You asked about the torque to <br /><br />get them off so I used a Torque wrench to see, none took more then 30 flbs.I <br /><br />hope you don't find what I did, one cylinder scored very badly. I'm sure the <br /><br />person I bought this from had this apart seen the problem and put it bad <br /><br />together just to sell. About your idleing problem, to get an idea if the carb <br /><br />is lean, let it idle and slowly close the choke plate by hand and see if you <br /><br />get a better idle. If you do then the idle needs a richer mixture ie: larger <br /><br />jets. The next thing to try is each venturi separtely. Take a pencil and while <br /><br />it's running block off the hole in the throttle plate one at a time. If it does <br /><br />not change for the better, the carb may be too rich or it is ok and your <br /><br />problem is elsewhere. Have you checked the Timing? What about the timing <br /><br />pointer position? Nscarpi Posts: 6 | From: Texas | Registered: Mar 2003 | IP: <br /><br />Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 27, 2003 10:42 AM Profile for SCO Edit/Delete Post <br /><br />Thanks for the info Nascarpi. The idle problem is longstanding, and early on a <br /><br />mechanic checked the timing and found the pointer off and reset it. I think <br /><br />just to be safe I should check it too. I've also been thinking of mounting a <br /><br />timing light and videocam on a tripod, and running wot just after sundown to <br /><br />check timing. The one lower cyl(still has 120 psi) worries me to suspect a bad <br /><br />gasket, ring, or score. I am going to try these suggestions this weekend. Ill <br /><br />recheck pressures all around too and report back. The ease of bolt removal does <br /><br />lend to the idea that the seller of your engine did in fact take those bolts <br /><br />off. The question now is this: What torque does it take to start yield of the <br /><br />head bolt? I could buy a new one and test this. Posts: 602 | Registered: Aug <br /><br />2001 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted March 27, 2003 01:05 PM Profile for sparkroost Edit/Delete <br /><br />Post the 1973 115/135 used high compression pistons/heads. If your fuel was not <br /><br />up to snuff wouldn't this cause bad idle? Back in 73 they had the good stuff! <br /><br />regular lead fuel.<br /><br />Just for curiosity sakes... couldn't you drill a small hole in each cavity on <br /><br />the intake manifold(4 of them) and put a vaccum gauge on it? I know this is how <br /><br />it's done on a 4 stroke, but 2 stroke I am not sure if this will work.<br /><br />Also I was told to set the timing at 20 deg full advance?(maybe 18, can't <br /><br />remember) for these old motors because of the high compression heads/pistons.<br /><br />something else to remember. Visually synking the carb plates is not close <br /><br />enough. disconnect the linkage and try and start the motor. It needs to be warm <br /><br />to do this otherwise it won't start. But when it does start look to see that <br /><br />it's trying to run. I could not get my engine to run at 800 rpm.. disconnected <br /><br />the linkage and it was idling at about 500!! So why not 800... hmmm.... the <br /><br />linkage was off between the two and they were fighting each other. Sometimes <br /><br />the shafts get worn(actually it's the brass bushings that get worn) and the <br /><br />shaft will "tilt" as they are actuated. This translates into "slop" and will <br /><br />throw off the carb synk. Cylinder compression is crutial in these motors cause <br /><br />the carbs can't be adjusted pr. cylinder. Posts: 59 | From: South | Registered: <br /><br />Mar 2003 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 27, 2003 05:25 PM Profile for SCO Edit/Delete Post <br /><br />Good points Spark. Does anyone know if the old leaded gas engines should be <br /><br />jetted to a special size, or is that built in to the OMC recommended jets? Same <br /><br />question for timing, should it be retarded? I use midgrade gas. Have heard <br /><br />premium can have gasahol and low grade is junk. Posts: 602 | Registered: Aug <br /><br />2001 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 27, 2003 05:33 PM Profile for SCO Edit/Delete Post <br /><br />On third thought, best for now to test each carb throat and look for a lean <br /><br />condition. I could even get undersize jets and drill and test till I find the <br /><br />right size Posts: 602 | Registered: Aug 2001 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted March 27, 2003 06:58 PM Profile for sparkroost Edit/Delete <br /><br />Post You cannot adjust the jets for high compression! You can only reduce <br /><br />timing, change head gasket thickness(with this you will need to change jetting <br /><br />also). Only problem changing the head gasket thickness would be loss of power. <br /><br />If you have a 115 for instance, you would drop it down to say 85hp with lower <br /><br />compression gaskets.<br /><br />Might be a fuel additive you could use to get the octane up. You could always <br /><br />fill up at the boat docks pumps as they usually have the good 103 racing fuel.. <br /><br />But... $$$$$<br /><br />If you have good compression you should be able to get it going like it is.<br /><br />As for drilling the orafices... those holes are a specific size as you know. <br /><br />Drilling them out can only create more problems for you. You would have to <br /><br />drill it out perfectly straight, otherwise you are gonna "wallow" out the hole. <br /><br />From your description you are loading up. If you load up on only 1 cylinder <br /><br />it's going to knock off the overall running of the motor. Would be very similar <br /><br />operation to uneven carb synk in the low speed range.<br />Just keep it in mind. What makes an engine run is compression, air/fuel ratio <br /><br />and a clear path for exhaust to get away from the cylinders. Also, to idle good <br /><br />you need to have good exhaust bypass. The majority of exhaust exits from the <br /><br />lower unit. There is a bypass hole in the upper end to release exhaust out the <br /><br />holes in the leg.<br /><br />I am not a professional by any means. But I have been around a few blocks. Just <br /><br />trying to help when I can. Please correct me if I have stepped out of bounds. I <br /><br />am always trying to learn. Posts: 59 | From: South | Registered: Mar 2003 | <br /><br />IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 28, 2003 01:27 AM Profile for SCO Edit/Delete Post I <br /><br />appreciate your input spark. Ive thought the cylinders to be fighting as it <br /><br />will often start enough to override the starter but not enough to sustain idle. <br /><br />fire die fire die etc. The compressions were all identical but one cyl deviated <br /><br />but as I recall that one was within limits. I like Joe Reeves approach, which <br /><br />is to take care of the basics first, the move on to the weird stuff. When I <br /><br />look at it this weekend though, I'll be glad to have other theories to <br /><br />consider. Posts: 602 | Registered: Aug 2001 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 28, 2003 10:52 AM Profile for SCO Edit/Delete Post <br /><br />Is it a tough job to check/clear any exhaust build up that could be causing <br /><br />excessive back pressure?( I realize this is the most unlikely cause of the <br /><br />problem.) Posts: 602 | Registered: Aug 2001 | IP: Logged<br />Joe Reeves<br />OMC Guru<br />Member # 6826<br /><br />posted March 28, 2003 11:11 AM Profile for Joe Reeves Edit/Delete <br /><br />Post SCO.... If you have compression and the proper ignition, The problem is <br /><br />usually found in the carburetion department as mentioned previously.<br /><br />One thing I neglected to mention... On a flushette, a 20" shaft length engine <br /><br />(height of transom at center) should have its idle set at 1000 rpm. A 25" shaft <br /><br />engine should be set at 1200 rpm. Perhaps yours is set too low?<br /><br />NOTE... Again, the above idle rpms pertain to being set while running on a <br /><br />flushette, not in the water.<br /><br />--------------------<br />Joe (30+ Years With OMC)<br />Posts: 791 | From: Central West Florida | Registered: Feb 2002 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted March 28, 2003 01:13 PM Profile for SCO Edit/Delete Post <br /><br />Wouldn't that be something. I am reading 1000 rpm on the flushette. I'll check <br /><br />the lu. Should the 20 inches be from the top of transom to the cavitation <br /><br />plate? Posts: 602 | Registered: Aug 2001 | IP: Logged<br />Joe Reeves<br />OMC Guru<br />Member # 6826<br /><br />posted March 28, 2003 02:22 PM Profile for Joe Reeves Edit/Delete <br /><br />Post Measurement would be from center top of transom to keel/bottom of boat. <br /><br />Cavitation plate would be approximately 3/4" below bottom of boat.<br /><br />--------------------<br />Joe (30+ Years With OMC)<br />Posts: 791 | From: Central West Florida | Registered: Feb 2002 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 09, 2003 10:10 AM Profile for SCO Edit/Delete Post <br /><br />Update. Problem still exists. I went through the carbs and replaced low speed <br /><br />jets with new .030, cleaned passages with omc engine tuner, and replaced all <br /><br />fuel line w new. The holes to the carb barrel are clear also. I'm reasonably <br /><br />sure that the carbs are not restricted in any way. All flappers and throttles <br /><br />appear to be syncronized, undistorted , and precise and operating correctly. <br /><br />The linkages are good and hooked up correctly. The start up was as before, pump <br /><br />fuel, full choke, neutral tHrottle up. 6 seconds crank till sign of life, then <br /><br />intermittent starts and stops as starter overcome, fially periods of runing for <br /><br />2 or 3 seconds with abrupt halts. Then finally sustained running to a pretty <br /><br />good idle. Once running , can stop and start with no problem . I got one extra <br /><br />clue. On one of the first sustained runs where the motor wouild have continued <br /><br />running, I lowered the throttle to idle, and the engine slowly lost momentum <br /><br />then finally died, so was fuel starved. When warm, the engine has no problem in <br /><br />the idle throttle position. Will check compression again next, and try some <br /><br />shots of premix in the throats. Any comments welcome. Posts: 602 | Registered: <br /><br />Aug 2001 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 09, 2003 11:58 AM Profile for sparkroost Edit/Delete <br /><br />Post Still sounds like link and synk or air leaking somewhere. You really can't <br /><br />link and synk by sight!<br /><br />Another thing to consider.. the carbs have a plug in them, about the size of a <br /><br />dime. Under that plug is your idle circuit. The idle circuit comes out 3 holes <br /><br />near the throttle plates. If you have an obstrustion in there you will get <br /><br />inconsistant idle. To be positive on the carbs not being it you will need to <br /><br />remove the plugs, all the jets and soak in berrymans carb cleaner. But you have <br /><br />to remove any rubber/nylon bushings from the throttle shafts. If you have to <br /><br />remove the throttle plates, be sure to get new screws and "peen" them over <br /><br />after re-assembly with loc-tite.<br /><br />Warm engine. Pull that linkage bar off the carbs. Start motor. Will she idle <br /><br />now?(will be really low idle). You may be surprised.. it might just idle at <br /><br />400-500 when you do this. If so, it's your lynk and synk! Remember, lynk and <br /><br />synk only applies to idle and off idle. WOT the engine does not care unless <br /><br />they are WAY off. Posts: 59 | From: South | Registered: Mar 2003 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 09, 2003 12:32 PM Profile for SCO Edit/Delete Post <br /><br />Thanks spark. I am ready to do the fingers tests(per Joe) and sync tests. I did <br /><br />remove the idle circuit core plugs and they are perfectly clean. The three <br /><br />holes are good to the barrel . At some point. someone had damaged one of the <br /><br />three carb casting holes when prying out the core plug on 1 of the 4 circuits, <br /><br />but it partially closed the hole and I filed it back to the size of the other <br /><br />identical one with an 031 drill bit. There was no observable distortion of the <br /><br />casting. I don't think it could be the problem though Ill keep it in the back <br /><br />of my mind. I cleaned all passages w the tuner and shop air soak repeat soak <br /><br />repeat.... The idle when warm on the muffs is good. Posts: 602 | Registered: <br /><br />Aug 2001 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 09, 2003 01:09 PM Profile for sparkroost Edit/Delete <br /><br />Post Sounds to me like you just named your problem.<br /><br />Look for another carb my friend.<br /><br />Goto hardware store...... Buy 4 1/8" nipples. Buy 1 vaccum gauge. Get a "T" and <br /><br />about 6' of 1/4" hose. You will also need 4 plugs(the rubber ones that fit over <br /><br />the 1/4" nipples(can't remember what there called).<br /><br />Take intake off. Drill 4 holes into intake, near the carbs. as close to center <br /><br />of throat as possible. 1 hole in each throat. Thread for the nipples you <br /><br />bought. Screw in nipples. Put rubber caps over nipples. Re-assemble.<br /><br />Remove 2 caps on the port side. Cut 2 pieces of hose 2ft and 1, 1 ft..<br /><br />Connect 2 ft. hoses to nipples and to "T". Connect 1 ft. hose to gauge and "T".<br /><br />now.. as the motor runs you are going to see the needle jump up and down. You <br /><br />can do a variety of things to dampen this out. You need to restrict the inside <br /><br />diameter of the hose to stop the jumping. Ideally you would use a valve inline <br /><br />at the gauge. Then you close it off until you have slight to no bounce. You can <br /><br />stick a drill bit in the hose also at the gauge. You just have to find the <br /><br />right size to get it where you want.<br /><br />One you get it running and up to operating temp you need to get it to idle, <br /><br />whatever it takes. if you have to increase the throttle, do it.<br /><br />Block off one line and check reading, block other line off and check reading. <br /><br />Adjust link and synk until they are even.<br /><br />Note vaccum readings for port side and verify starboard side is the same or <br /><br />within 2 in. hg.<br /><br />On another note. Did you remove your exhaust plate on the back and check for <br /><br />carbon blockage? Posts: 59 | From: South | Registered: Mar 2003 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 09, 2003 02:13 PM Profile for SCO Edit/Delete Post <br /><br />Maybe so, but it's just a scratch, how finiky can these things be? I didn't <br /><br />check the exhaust for carbon. I like the techniques you mention, but makes me <br /><br />think that if reeds not equal or there is some internal leakage this method <br /><br />will mask those probs( maybe a good thing). Do you think I should check <br /><br />cranking vacuum on all 4 intake ports first? I think I could do that with a <br /><br />piece of sheet aluminum with a gauge on it duct taped to the intake with <br /><br />throttle set at full. <br /><br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 15, 2003 11:23 PM Profile for SCO Edit/Delete Post <br /><br />I've posted about this motor. I want to see if what the carbs see is adequate <br /><br />suction while cranking to get enough fuel into the cylinders to start <br /><br />adequately. I am thinking I can hook a vacuum gauge to a flat aluminum plate <br /><br />and duct tape that plate to the 2 barrel carb intake or even take carbs off and <br /><br />duct tape to intake ports one at a time to test. Problem is I have nothing to <br /><br />compare to, what woud be a good vacuum. Has anyone done this or other? What do <br /><br />you do to test this? Thanks SCO Posts: 670 | Registered: Aug 2001 | IP: <br /><br />Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 16, 2003 02:00 AM Profile for sparkroost Edit/Delete <br /><br />Post the duct tape thing is not going to work. You will need to drill holes in <br /><br />your intake manifold or your carbs. It's not a number thing. It's like <br /><br />compression. You want to be the same vaccum on all 4 intakes, within 2 inches <br /><br />hg is ok.<br /><br />If it is off more that 2" top to bottom you will have to adjust your link rod <br /><br />that goes from the top carb to the bottom one. If it's not adjustable, get one <br /><br />that is or make one out of remote control parts from a hobby store.<br /><br />Try and remove the rod that connects the top carb to the bottom one for the <br /><br />throttle plates. Start engine(warm engine before doing this). Will it <br /><br />idle?(will be very low idle, like 400-500). If it sounds like it is trying to <br /><br />idle but is just a bit too low idle and stalls.... increase the idle, have <br /><br />someone start motor for you while you push up slightly on the lower throttle <br /><br />shaft. You will know when you get it in the right area.. If you are far off the <br /><br />engine will die and cough abruptly. Try and fine tune your lower throttle shaft <br /><br />until it idles........Did you get it to idle?..... it's now time to make an <br /><br />adjustable rod so you can synk your carbs together. Posts: 113 | From: South | <br /><br />Registered: Mar 2003 | IP: Logged<br />clanton<br />Admiral<br />Member # 2789<br /><br />posted April 16, 2003 04:57 AM Profile for clanton Edit/Delete <br /><br />Post You can check the vacuum at the fuel pump pulse connection, which show the <br /><br />vacuum on the one cylinder, should be close to 6 lbs. Linkage is adjusted at <br /><br />the carb. If hard starting or rough idle, check timing sensor gap, and carb <br /><br />throttle shaft/body for wear. Posts: 2138 | From: Immokalee,Florida | <br /><br />Registered: Jul 2001 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 16, 2003 10:54 AM Profile for SCO Edit/Delete Post <br /><br />So the timing sensor gap, if too great, would mean the starting rpms not <br /><br />adequate to put out a strong timing pulse I take it. I hope that gap is <br /><br />adjustable. Thanks. I will instrument this thing if all fails sparkroost. <br /><br />Thanks for the tips. Posts: 670 | Registered: Aug 2001 | IP: Logged<br />Joe Reeves<br />OMC Guru<br />Member # 6826<br /><br />posted April 16, 2003 11:03 AM Profile for Joe Reeves Edit/Delete <br /><br />Post SCO.... I've been reading through the posts and am somewhat puzzled. These <br /><br />engines aren't really that technical or difficult to restore to the factory <br /><br />settings. Are you thinking about entering that engine in the Indy 500? (Grin)<br /><br />--------------------<br />Joe (30+ Years With OMC)<br />Posts: 818 | From: Central West Florida | Registered: Feb 2002 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 16, 2003 12:25 PM Profile for SCO Edit/Delete Post <br /><br />I'm with you Joe. How can it be that tough? It must be something simple. I'll <br /><br />take it out this eve and load the barrels w premix and see if she starts <br /><br />better. That should isolate the problem to fuel delivery, pure and simple. Do <br /><br />you agree? Posts: 670 | Registered: Aug 2001 | IP: Logged<br />Dhadley<br />Admiral<br />Member # 685<br /><br />posted April 16, 2003 03:09 PM Profile for Dhadley Edit/Delete <br /><br />Post We built those plates a few years back for a looper. We just duplicated a <br /><br />carb base gasket in aluminum with a threaded hole over the venturi. Then with a <br /><br />vacuum gauge hooked to each we turned it over. I dont remember what the numbers <br /><br />were but they were all about the same.<br /><br />Your motor should have no problem starting if all is stock and as produced. <br /><br />Check the stuff Clanton mentioned. If you arent satisfied with the choke system <br /><br />you can install the newer injector style primer.<br /><br />Good luck! Posts: 2178 | From: Port Charlotte FL | Registered: Feb 2001 | IP: <br /><br />Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 16, 2003 05:40 PM Profile for SCO Edit/Delete Post I <br /><br />just finished testing on the flushette. I made up a plastic spray bottle of <br /><br />premix(spray and wash bottle I think), and gave it a shot in each of the 4 <br /><br />barrels prior to first start. I was surprised that it didn't catch immediately. <br /><br />It took the full 6 seconds to catch but started at first catch and stayed <br /><br />started. Yea. Thats the way I want the motor to run!! I still have to test in <br /><br />the water, but things look good. I had the carb cover off, and noticed that <br /><br />when I cranked the choke flappers opened slightly. I put it on manual full <br /><br />choke and again got the same result. I concluded that the suction was good and <br /><br />forced the choke flappers to open slightly. Let me know if that indicates a <br /><br />problem, and that maybe the choke closing force is not enough. Thanks getting <br /><br />near the end I think. Posts: 670 | Registered: Aug 2001 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 16, 2003 07:00 PM Profile for sparkroost Edit/Delete <br /><br />Post The choke flappers should stay closed, not patially closed, closed. This <br /><br />will draw in more fuel during startup. Adjust your linkage so when switched on <br /><br />they are fully closed.<br /><br />BTW, this has nothing to do with idle. Posts: 113 | From: South | Registered: <br /><br />Mar 2003 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 16, 2003 11:15 PM Profile for SCO Edit/Delete Post <br /><br />The idle sounds ok for now spark. The choke is designed to close via spring to <br /><br />a solonoid (or mechanical button). I think I can get a little more closing <br /><br />force from the solonoid spring as it is not set up exactly right, but think it <br /><br />may not be able to overcome that suction force by design. Ill check those brass <br /><br />choke air tubes also to make sure they are completely unobstructed. Once I get <br /><br />this thing starting I am going to recheck the timing and fine tune the idle. <br /><br />Posts: 670 | Registered: Aug 2001 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 17, 2003 01:05 AM Profile for sparkroost Edit/Delete <br /><br />Post Ditch the spring. Be creative. [Smile] Posts: 113 | From: South | <br /><br />Registered: Mar 2003 | IP: Logged<br />jimd<br />Captain<br />Member # 18514<br /><br />posted April 17, 2003 09:40 AM Profile for jimd Edit/Delete Post <br /><br />I'm with sparkroost on the choke plates. I don't know exactly how your engine <br /><br />works but when I choke an engine I want to choke the mother. I will be the one <br /><br />to undo the choke not some namby pamby spring!! Anyway, on my Suzuki the choke <br /><br />linkage is direct and when I choke it it stays choked. Completely. Posts: 180 | <br /><br />From: St. Petersburg, Florida | Registered: Jan 2003 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 17, 2003 11:09 AM Profile for SCO Edit/Delete Post I <br /><br />agree with you both in one sense, that it is the best, but, if the engine <br /><br />allows some flap movement when at factory spec then shutting that choke flapper <br /><br />manually could be considered a workaround, and an avoidance of the real <br /><br />problem.<br /><br />Joe, Dhadley, Clanton,<br />Do ya'll notice some choke flapper opening because of the suction airflow <br /><br />forcing them open silghtly when cranking as a normal condition on these v4's? <br /><br />Posts: 670 | Registered: Aug 2001 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 17, 2003 11:40 AM Profile for sparkroost Edit/Delete <br /><br />Post I believe you have a thermister on your engine connected to the choke. <br /><br />That thermister will create a votlage drop across it when it's cold. This is <br /><br />for warm up purposes so that the choke is partially closed to create more <br /><br />vaccum. The spring is used so that if the thermister is working and you floor <br /><br />the engine, the vaccum will overcome the spring and open the plates.<br /><br />Remove thermistor and spring(or shorten the spring) and you will have much <br /><br />quicker starts.. That is what you wanted, right?<br /><br />Heck, by now that spring does not have the tinsel strength it used to... Posts: <br /><br />113 | From: South | Registered: Mar 2003 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 17, 2003 11:57 AM Profile for SCO Edit/Delete Post <br /><br />Sparkroost, these are good suggestions, and I will employ them or some other <br /><br />way to get that choke closed all the way when cranking. I agree that the <br /><br />automatic choke function is worthless! But for now, I want to keep problem <br /><br />solving till I get the motor to factory spec, then I will improve from there. I <br /><br />think the spring might be to avoid damaging the choke mechanism if misadjusted. <br /><br />The throw of the solonoid gos past the close limit of the choke and spring load <br /><br />s it shut. Posts: 670 | Registered: Aug 2001 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 17, 2003 12:11 PM Profile for sparkroost Edit/Delete <br /><br />Post I don't belive the choke solenoid is strong enough to break the choke <br /><br />plates or linkage. If this is a concern, adjust the linkage with the choke <br /><br />engauged, then you won't have a problem.<br /><br />Factory spec... you will need a rebuild for that to make things "a perfect <br /><br />world"..<br /><br />I find it amusing that you want factory spec, but don't want to improve your <br /><br />condition. You are asking for quicker starts, but want it the factory way. The <br /><br />motor is 30 years old! Make it work for you. Posts: 113 | From: South | <br /><br />Registered: Mar 2003 | IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 17, 2003 12:14 PM Profile for sparkroost Edit/Delete <br /><br />Post Just remember.. the choke solenoid plunger is a piece of metal. The <br /><br />solenoid housing is a coil of wire. When 12V is applied it acts as a magnet and <br /><br />sucks the plunger down. There are no mechanical parts connecting the plunger to <br /><br />the choke housing. Posts: 113 | From: South | Registered: Mar 2003 | IP: <br /><br />Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 17, 2003 12:41 PM Profile for SCO Edit/Delete Post <br /><br />Sparkroost,<br />I am not saying what will happen if I change the spring design, I am offering a <br /><br />speculation about the unintended consequences that go with modifying an <br /><br />engineered design. We don't know what went into the design of the mechanism. <br /><br />Also I find it amusing that you do not see the logic of getting the motor to <br /><br />factory spec prior to making these improvements. I want to exhaust that <br /><br />possibility first.<br /><br />quote:"There are no mechanical parts connecting the plunger to the choke <br /><br />housing. " true, but the plunger has a significant mass and gets to high speed <br /><br />when coil is activated. A rigid linkage could transfer a big force to a <br /><br />slamming choke flapper. You may be correct about the thermistor, but maybe also <br /><br />there is more to the design.<br /><br />Don't think I'm angry here, I actually enjoy jawing about it. [Eek!]<br /><br />Also, for now, I am not just asking for quicker starts, just starts. It just <br /><br />barely starts , and I want to make sure there is not another problem that I am <br /><br />overlooking. I took the boat on a campout, and was almost stranded in the <br /><br />boonies because of this start problem. Posts: 670 | Registered: Aug 2001 | <br /><br />IP: Logged<br />sparkroost<br />Captain<br />Member # 20588<br /><br />posted April 17, 2003 12:52 PM Profile for sparkroost Edit/Delete <br /><br />Post Sometimes things look good on paper, but in the real world there function <br /><br />does not equate to the paper it was written on.<br /><br />You proved that you have a fuel delivery problem with the pre-mix. Go a step <br /><br />further and you will have that problem solved. Then you can move on to other <br /><br />things.<br /><br />I am just trying to help ya SCO. If you want to keep the spring... buy a new <br /><br />one. Adjust the linkage so that they close all the way, and be done with it <br /><br />[Smile] Posts: 113 | From: South | Registered: Mar 2003 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 17, 2003 01:03 PM Profile for SCO Edit/Delete Post <br /><br />NP Sparkroost, youre an iboats brother, and I appreciate your help. Maybe I am <br /><br />too cautions, but, I pay the price if things go wrong. I don't mind taking <br /><br />time. Posts: 670 | Registered: Aug 2001 | IP: Logged<br />jimd<br />Captain<br />Member # 18514<br /><br />posted April 17, 2003 02:05 PM Profile for jimd Edit/Delete Post <br /><br />As a diagnostic aid, disconnect entirely the linkages to the choke butterfiles, <br /><br />and manually hold all of the butterflies completely closed (I don't know how <br /><br />many carbs you have, you may need a hand) while someone else turns the key. See <br /><br />if there is any improvement. If there is you know the way to go, if not you can <br /><br />say nah, nah I told you so and I'll go home. Posts: 180 | From: St. Petersburg, <br /><br />Florida | Registered: Jan 2003 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 17, 2003 02:42 PM Profile for SCO Edit/Delete Post <br /><br />Jim, I know that it will work better to force those flappers completely <br /><br />closed(unless the force required to keep the flapper closed during crank would <br /><br />bend a flap as the air under suction may not be denied). I even think I <br /><br />probably dont have enough closing force which might be the entire cause of this <br /><br />poor start problem. I just want to know if it is normal for those flappers to <br /><br />open slightly when cranking. If that is the case, then something else is wrong <br /><br />if I have normal choke flapper closing force and the engine doesn't start <br /><br />right. If Joe Reeves says "no, those flappers should be shut tight even during <br /><br />the crank" then I will know the opening flappers during crank to be the problem <br /><br />that I have. Considering the amount of air sucked in during crank, and the <br /><br />small fuel idle ports, I am not sure that the flaps are meant to be 100% closed <br /><br />during crank. A 3-1/2 inch piston will pull a lot of air. Posts: 670 | <br /><br />Registered: Aug 2001 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 17, 2003 02:50 PM Profile for SCO Edit/Delete Post <br /><br />What do I think?? the same as you Jim and Spark. I am just trying to settle the <br /><br />question. Posts: 670 | Registered: Aug 2001 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 17, 2003 02:59 PM Profile for SCO Edit/Delete Post <br /><br />Dhadley says it should be fully closed during crank. I shall now find out how <br /><br />to make that happen. Problem probably solved. You can see how this can happen <br /><br />can't you, you set up statically, but when you start dynamically, things <br /><br />change. Thank you all. I will dutifully report the result. Posts: 670 | <br /><br />Registered: Aug 2001 | IP: Logged<br />SCO<br />Captain<br />Member # 3929<br /><br />posted April 18, 2003 12:03 PM Profile for SCO Edit/Delete Post I <br /><br />taped the choke closed and cranked. Didn't start right away(7+ sec) but I think <br /><br />that was because I did this with the throttle closed. Soon fuel was pouring out <br /><br />of both carbs. When it started, goop was sprayed out the exhaust. I apparently <br /><br />loaded it up. I get one of these tests per day. I am going to try again today <br /><br />with choke taped shut and neutral throttle pulled up to 1/2. <br /><br />This is a condensed compilation of 2 threads so as to have the history in one place.
Is there any way to operate the chokes by hand without the tape so that if it burps once you can let them off?