Will only idle on choke

stl

Petty Officer 1st Class
Joined
Jan 22, 2005
Messages
346
Let me start with a brief history. I have a 1964 5.5 hp Johnson cd-21a. Over the winter I rebuilt the carb. I must mention at this point that I am an new to engine repair of any type. I thought the carb rebuild went pretty well, aside from a poor idle, which I was willing to deal with. It has idled a little high since the rebuild. I think the poblem was that I never really fully understood the low speed needle adjustment. The motor was ran a month ago it seemed to run fine except for the idle. My buddy was driving so I am not sure if he had the choke on or not. Yesterday I tried to run it. It would only run on choke. It ran for a few minutes and died I could not start it for the rest of the day. It sounded like it was not getting feul. It would start and die after a few seconds. I brought it home took the carb off and found a very deteriorated feul line leading to the bowl. I took the carb apart and found a bunch of black gunk from the fuel line. I soaked it an cleaned out all passages, replaced the fuel line, thought I had it. It will start on choke and only run on choke. I can actually get it to idle to a tick, but as soon as I push in the choke, even a little bit it starts to die. I can keep going for a few seconds longer if I squeeze the bulb. If I put the choke back on it fires back up. Could it be the dreaded low speed needle adjustment? If so I have lost my place and need to start from scratch. Please help.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Will only idle on choke

Depending on which carburetor you have (1 or 2 adjustable valves), the following should be of help to you. Make sure the carburetor is absolutely clean to avoid misadjustments.<br /><br />(Carburetor Adjustment - Single S/S Adjustable Needle Valve)<br />(J. Reeves)<br /><br />Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.<br /> <br />Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.<br /> <br />Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting. <br /> <br />Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.<br /><br />When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.<br />-------------------------------------------------- <br />(Carburetor Adjustments - Two Adjustable N/Vs) <br />(J. Reeves)<br /><br />Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns. <br /><br />Setting the high and low needle valves properly:<br /><br />NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle va /lve adjustment.<br /><br />(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting. <br /><br />(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting. <br /><br />When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
 

stl

Petty Officer 1st Class
Joined
Jan 22, 2005
Messages
346
Re: Will only idle on choke

Well I was all geared up to try the above procedure this morning,but I have one problem. Now the motor won't start at all. Every once in a while it will turn but quickly die, like it is not getting any fuel. It will fire if I squirt fuel in the carb, but again quickly die. Will running a motor wiyh the choke on as I did yesterday foul the plugs or cause any other problems? At least yesterday I could get it to go a little bit. Thanks in advance for any suggestions.
 

cvx35

Petty Officer 2nd Class
Joined
Jan 13, 2004
Messages
103
Re: Will only idle on choke

This particular model engine has no highspeed adjustment. It has a fixed orifice. As for slowspeed, there is an expansion plug at the top of your carburetor. Under that plug there should be 2 or 3 pin sized holes. It is possible that you have fuel hose debris in these holes. It's easy to miss. When you replace the plug, be sure to use gelseal around the edge.
 

Goldfish

Seaman
Joined
Mar 21, 2005
Messages
50
Re: Will only idle on choke

sounds like you still have garbage in your highspeed jet (the tube from the bottom of the bowl to the venturi tube). I would personally use a thin piece of copper wire and carefully, without reaming it any bigger clean out the tube. Then run compressed air through all the passages that you can find. Just for kicks, pull the fuel hose off the carb, and prime the bulb, make sure that you are actually getting fuel to the carb :)
 

stl

Petty Officer 1st Class
Joined
Jan 22, 2005
Messages
346
Re: Will only idle on choke

I did take the carb off yesterday and cleaned out that passage. Like I said I did get it to run , but only on choke. It was running when I quit yesterday. Do you think some gunk could have settled somewhere overnite? I am pretty new at this so it takes me a while to disassemble the carb. I kind of dread doing it again, but I guess Ill have to. As for the gel sealer mentioned above I think I read somewhere to use 1000 sealer which I can't find. Do you think Wal Mart or an auto parts store has a suitable sealer?
 

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: Will only idle on choke

Just to add to what others have said above. Your description is that of a lean idle mixture. The idle mixture is controlled by your "dreaded" idle screw. It should have no effect on high speed operation which is controlled by the high speed jet in the bowl (apparently fixed, not adjustable). If the screw is set approximately correct as according to Walkers instructions and the engine still needs choke to run the problem is likely fuel supply restrictions due to crud in the carbs somewhere or an air leak or both. The choke merely enrichens the mixture and is normally only needed for cold starts. Many people do an inadequate job of carb overhaul/cleaning particularly if they are relatively inexperienced. You should have a manual for reference. Carbs should be completely dismantled, orifices cleaned with carb cleaner AND (this is important) compressesd air (buy a can of air at Radio Shack if you don't have a compressor). The float valve should be replaced and the float height and idle screw should be set to specs. Use new gaskets and make sure there aren't any air leaks on reassembly.<br /><br />You also mentioned that pumping the fuel bulb had some affect so you might replace the diaphragm in the fuel pump while you're at it.
 

stl

Petty Officer 1st Class
Joined
Jan 22, 2005
Messages
346
Re: Will only idle on choke

You guys are awesome. I took the carb apart again. You would not believe how much more gunk from the old fuel line I pulled out of there. I don't know if I overlooked it the first time, or it settled there overnight. Anyway Joe I followed your procedure for the low speed needle adjustment and shes idleing better than ever. I have learned so much from everyone on this web site. thanks again.
 

cvx35

Petty Officer 2nd Class
Joined
Jan 13, 2004
Messages
103
Re: Will only idle on choke

Hey man, you need to make sure the fuel hose you replaced is "fuel hose". Glad you got it running.
 

stl

Petty Officer 1st Class
Joined
Jan 22, 2005
Messages
346
Re: Will only idle on choke

It was fuel hose. I did have to buy it a lawn mower repair shop. The guy said it was made by Briggs and Stratton. That sould be ok, right?
 
Top