55EL78S Need some advise please(long)

[OLDIRON]

First off, I do have the original factory manual. That aside, here's the complete story.
When I got this motor it had sat for along time. I got it to run but #2 was dead.No spark. Here's what I have done so far.
Replaced water pump impeller.New grommets, the works.
New power pack.
New coils,includining wires and plugs.
Compression check. 130 on each cylinder.
Rebuilt carbs. New BRP OEM kits. With new floats, welsh plugs removed. Cleaned throughly and blown with compessed air. Floats adjusted to fac. specs.
Oh..By the way..I did this twice. And actually, the carbs were very clean origanally for a 30 something motor.
Did all the tests for the health of the stator using a Fluke ohmmeter.Everything tests OK.
This thing throws a wicked spark. 1/2" no problem.
The problem is a bad miss. At idle and at WOT. Also after a running at WOT, the hot horn will sound, and yes the block is getting alittle too hot for my fingers.
The motor will run smooth for a few seconds, and then it will miss.Almost like you turned the key off. I have gone through all the wiring, and connections a dozen times. While it is running I disconnected the big red plug leading back to the command center...no change. This is a magneto ignition by the way, so after starting, the battery is out of the loop.
I cannot check the output of the stator because I donot have a DVA adapter.But everything ohms out good and it does have good spark to both plugs. Yes, I know it sounds like a fuel delivery problem, but eveything in that department seems to be OK. Pulled #1 plug wire at Idle and it missed worse.Pulled #2 at idle and it missed worse.Pulled both plug wires and it didn't run at all. Ha Ha, just kidding. The only thing I have not done is a fuel pump replacement. But it seems to be pumping fine, I did not put a pressure gage on it but I believe it to be pumping at least the 1 to 2 psi spec. just buy disconnecting the output line.The overheat problem maybe that one or more cylinders are running lean. But would that acount for the constant miss. Sorry for the long version, but I wanted to give you guys as much info as I could. I'm pretty much at my wit's end here. Any help or ideas what to do next other then junking it. The motor otherwise looks to be in excellent condition for a 30 year old motor and was well taken care of. Thanks for listening.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

I gotta bump this. Any ideas? I guess my next step is to pull the flywheel and check the condition of the sensor for any loose screws or signs of damage, although electricly every thing checks out good.

 

[ondarvr]

Re: 55EL78S Need some advise please(long)

You say it will run on one cylinder but miss, correct?

If the miss is like someone turned off the key for a second, then it is more likely electrical.

A rough stutter would be too much fuel, slowly dying and picking back up is too lean.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

You say it will run on one cylinder but miss, correct?

If the miss is like someone turned off the key for a second, then it is more likely electrical.

A rough stutter would be too much fuel, slowly dying and picking back up is too lean.

Sorry, I haven't had a chance check any posts here. Yes, it will run on one cylinder, but not well. Dosn't matter which one. Hard to describe the way it will behave, but is goes something like this. It will start right up with just a couple of cranks. Then it will run smooth, then all of a sudden she will miss and the whole motor will buck. Then it will smooth out again for maybe a couple of seconds, then it will do the same thing over again. I can increase the speed but it will do the same thing through out speed ranges. I havn't hade a chance to pull the wheel yet. Maybe this weekend. I tried giving it a little choke by hand dosn't seem to change anything. Do you think it could be a head gasket? Can a head gasket fail eventhough it has 130 in each hole and shows no sign of wet plugs? That may explain the hot horn at increased speed. Can't really see any steam though. Would a leakdown test show anything? I've never done one on a two stroke. Will it even work on a looper? Sorry for all the questions, but I really need some help on this one. Thanks.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

If anyone else has any ideas don't hesitate to chime in. I will try to answer any questions the best I can. I don't want to throw parts at it, and I don't want to tear into the motor unless I have to. By all accounts and the work I have done sofar, this motor should be ticking over smooth....but it dosn't. Thanks all.

 

[Brokeback Johnson]

Re: 55EL78S Need some advise please(long)

Miss could be water getting in. I would replace the head gasket and probably the exhaust manifold gaskets. Cheap and easy to do. The overheat problem points in this direction.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

Miss could be water getting in. I would replace the head gasket and probably the exhaust manifold gaskets. Cheap and easy to do. The overheat problem points in this direction.

Thanks for the input.Cheap, yes. I'm not so sure about the easy part. The plugs are not wet as far as I can see. But if I have good compression, a wicked spark and what as far as I can tell good fuel ( If I go through the carbs one more time it will be the thrid time) what's left? I synced the carbs as per factory specs. I haven't done a timing yet because I haven't gotten it to run to that point, but with a timing light and running it up to WOT I get pretty close to 19 degrees. Even with the miss. I know this may not be an easy one to solve. But hay, if it was easy, my wife would be working on this motor. I'm leaning to your take that it may be a head gasket rather then running lean. I hope we are both wrong. Thanks man.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

OK guys. I pulled the flywheel today and I found nothing loose or out of order. Ingnition ,or fuel wise I can not find anything wrong with this motor. I'm leaning now to either a head gasket or an exhaust gasket. I have done an extensive search of threads here and it sounds like it may very well come down to one or both. I would like to eleminate the head gasket. Because that's not gonna have a high replacement enjoyment factor. My question here is if I have 130 psi on each hole, could it still be a head gasket? Whata ya think? Thanks.

 

[Mntom]

Re: 55EL78S Need some advise please(long)

If you have 130 psi each hole the head gasket is fine. I find it hard to believe that you have a water issue. If you did the plug where the water is getting to would look cleaner than the rest. An intermittent miss is almost always an electrical issue (my experiences anyhow). Do you have a timing light? If you do hook it up to the cylinder with the miss and see if you are loosing spark. That would eliminate or confirm a spark issue.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

If you have 130 psi each hole the head gasket is fine. I find it hard to believe that you have a water issue. If you did the plug where the water is getting to would look cleaner than the rest. An intermittent miss is almost always an electrical issue (my experiences anyhow). Do you have a timing light? If you do hook it up to the cylinder with the miss and see if you are loosing spark. That would eliminate or confirm a spark issue.

Thanks for the response. Having good compression in each hole when it's hot or cold tells me also that the head gasket should be good, but I wasn't sure. Yes, I did put a timing light on both wires and by looking at the light it doesn't seem to miss a beat on either plug. Put brand new plugs in it twice, in the unlikely event that one new plug could be defective. No change. New plugs, new coils,new cd pack,new wires, throws a nasty 1/2" spark, stator output is within specs,no wet plugs. Carbs gone through twice, checked fuel pressure,replaced fuel lines,filter is clean,new fuel mix.Decoked with Seafoam twice.Reeds are clean and not bent or broken, new intake gaskets. What's left? What am I missing? I am at a complete lose on this motor. About the only thing left is to pull the exhaust baffle and check that. Maybe a small amount of water is getting into the holes and steaming off so fast that I'm not seeing it on the plugs. Also I will pull the fuel pump off and check to make sure the diaphram isn't letting fuel into the case.I donno, this one has me scratching my head. Any ideas, and I mean any ideas, will be appreciated, thanks.

 

[AlTn]

Re: 55EL78S Need some advise please(long)

I'm with brokeback on this one...the fact that your compression is exactly the same for each cylinder can indicate leakage between cylinders...overheat can indicate leakage of exhaust into water jacket..timing light on both plug wires shows no skip or weakness in voltage output?..does it "smoothout" if you spray fuel mix into the carbs?...

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

I'm with brokeback on this one...the fact that your compression is exactly the same for each cylinder can indicate leakage between cylinders...overheat can indicate leakage of exhaust into water jacket..timing light on both plug wires shows no skip or weakness in voltage output?..does it "smoothout" if you spray fuel mix into the carbs?...

Thanks Altn. Compression veries somewhat between cylinders 125-130 depends on cranking speed and how long. What I'm trying to say is that they are not actually equal at all times. Does that make any difference? I usually crank about 5 or 6 times. No skip or weakness with timing light. I'll try the mix directly in the carbs later today and let you know. I'm kinda leaning to the exhaust gas leakage also. Today I looked over the manual again and noticed something. In the manual it shows the timing stop to be about halfway out. So I went to YouTube and saw some other 55s and the timing stop was also approx. halfway out. Mine is screwed all the way down. I did not mess with the timing yet. It was like that when I got it. Just read the Reeves wot not running sticky. I thought the motor had to be running correctly before you could check timing according to the shop manual. Apairently not the case. If the timing was too far advanced, wouldn't that cause the motor to heat up and run lousey at wot? Don't know if that has anything to do with the stutter though. Maybe I have two or more different things going on here. Thanks again for the input. Keep um coming!

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

When I first put a timing light on this I thought it was running at close to 19 deg. But right now I'm thinking that I read it wrong. When I get some time this afternoon, I will try the Reeves method. Resync the carbs and try the premix squrit into each carb if the timing turns out not be be the issue. Maybe my timing is compleatly haywire. I was almost ready to junk this one. But I can't now. It's become too much of a challange and I don't give up that easy. I know that with you guy's help and some work this thing is gonna run right. Just not sure when.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

Ok guys. Today is the first chance I had to really work on this motor. and here's what I did. With a good strong battery that I charged up overnight, I started it up, ran it for about 5 minutes. Pulled both plugs and hooked them to my homemade spark tester. Put my comp guage on #1 and cranked it about 6 reves. 128 + or -. Did the same on #2, 128 + or -. That tells me my head gasket should be ok. Then I put my timing light on #1 and did the Reeves timing thing. I had to adjust the rubber stop to get it to roughly 4deg. before 19 deg. Like I said before, someone had screwed the advance stop all the way down. So the motor was insanely advanced at wot. Now it will run as fast as I dare to on muffs without overheating. The hot horn use to go off at half throttle after a short time. I can't believe this thing didn't blow along time ago. Next I checked the spark on my tester, still a good 1/2" blue solid spark. But I still have a stutter or miss at all speeds. So I take the fuel line off the pump output while it's running, by the way I don't advise everyone to do this, it's not really the safest thing to do having fuel squirting, and I quickly attach a hose leading into a plastic bottle. It's pumping fuel great and the motor keeps running until the fuel in the carb bowl runs out.That to me elimantes the pump. Now I take and put some fuel in a spray bottle and while it's idleing I give both carbs a shot. No change. But when I rev the motor and give them a shot, I had to experiment a little here with different distences from the carbs, I got it to smooth out some. So.....looks to me that it may be a fuel issue and I will have to go back into the carbs for a third time. I can't believe there would be a problem after the first rebuild, but it sure is looking that way. Can you guys think of anything else to check? I did find that my rectifer is bad. Who knows what caused that. My guess is somebody reversed the battery leads before I got it. All it takes is one shot and the diodes are wasted. For now I just disconnected the rectifier because at this point keeping my battery charged is not a concern. Anything I should look for on this third time carb rebuild? The shafts are nice and tight, no slop. New floats were installed. What else? Thanks in advance guys. I will let everyone know what happens.

 

[Mntom]

Re: 55EL78S Need some advise please(long)

Congrats on figuring some of it out!! You say that it acts up when you rev it up so that tells me that the problem now lies with the high speed circuit in the carb(s). It just might be something a simple as taking an air hose and blowing out the high speed jet.

 

[Tim Frank]

Re: 55EL78S Need some advise please(long)

May actually be a film of varnish built up on jet reducing diameter. Manual should give you a drill size to use as reference to clean it.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

Thanks guys. I think I got the timing and overheat problem licked. Today I took the silencer off and pulled the low speed jet plugs out again. I never took any of the low or high speed jets out because I didn't have the special tool to remove them, I just sprayed them really good and blew compressed air through them. Without taking the carbs off today, I sprayed more cleaner into them and after that, I got it to smooth out a little better. Also, on a whime, I ran it with the motor tilted all the way up, and also with it all the way down. There is a difinate change in the way it runs. Seems to run better not tilted down where in would normally plane. Float setting wrong? I don't know how I could have gotten that wrong, I set them according to the manual. Well, the only way to know is to tear into them one more time.But I feel this problem is now fuel related. I will let you know what happens. Maybe this will help someone else with the same problem on a 30 something 55 horse. Thanks again.

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

Ok guys.Are you ready for the final outcome? Well, here it is. I just couldn't go through these carbs one more time. In my heart, I knew these things were squeaky clean. I was getting fuel,I was getting spark, now at the right timing, I was getting good compression. Here is what I was doing wrong. I was trying to tune this motor on muffs. I can't say for other motors, but on this one,it just can't be done. The one thing I was was missing was back pressure! I was reading a few threads here on this subject, and I thought the one thing I have not done was put it in a tank. The first thing I noticed is that the motor smoothed right out at idle. Next I noticed a really strong and steady spray out of the indicater. Also something I have never seen before is water and exhaust coming out of the two opening slits just below the power head. I could not put it into gear because the garbage can I had was at the bare minimum of prop clearence. And I do not have a test disc prop in my tool arsenal. I throttled her up after warm up and she ran like she was scared. No hot horn !!!! Well, the whole problem boiled down to this. A test tank. Can you believe it?. The motor did need all the parts I put into it to get it to this point. After all it is a 30 something motor. Just wanted to let you guys know the outcome. And by the way....thanks everyone for all the help. This old horse runs like new now. I will buy a new rectifier. The alternator is putting out around 20 vac at idle between the yellow wires, so I atleast know that it's ok.

 

[AlTn]

Re: 55EL78S Need some advise please(long)

thanks for posting the final results and glad to read of your happy outcome..

 

[OLDIRON]

Re: 55EL78S Need some advise please(long)

thanks for posting the final results and glad to read of your happy outcome..

Thank you. I belong to an older car forum also. And you know what just bugs the hell out of me is that someone asks a question, and I think, man, that sounds just like the problem I'm having. But they never post back if they fixed it. I don't want to be one of those people. And I hope this will help someone else.That's what a help forum is all about...right?