Lawn Boy 8238AE Running rich

16 years ago

Last year, my 8238AE started running real rich, even with the mixture screw turned all the way in. My son noticed that it was spitting out of the carburetor. I reasoned that it was running rich because it was drawing air through the carb twice. We checked the reeds, and they looked fine. I had my son pull the muffler to check the ports and he found the lower crank seal was leaking oil and one of the ports was about 1/2 closed. We cleaned out the ports, replaced the seal, replaced the spark plug, and it ran much better, but I had to keep the mixture screw all the way in.

This year when I started it up, it ran lean (I had to keep pumping the bulb to keep it running). I fattened up the mixture screw about a turn out and everything was fine....for a couple of weeks, then it got rich again.

I changed the float. The old one did have some scuff marks on it. No help. I adjusted the float lower so that the primer would barely work, and also cleaned out the air cleaner element. Very little help, still rich (the mixture screw is all the way in). It leans out a little when you remove the air cleaner, but it's still rich, and power is way down. It's still spitting lightly out of the carb, but that's way reduced now.

Now a new thing has happened the last couple of weeks. On a cold start, it's real rich for about 5 minutes, then slowly leans out enough to run almost normal, but power is still low.

I read on this site about cleaning out a clogged muffler. Does this sound like it might be the problem? How about the top crankcase seal? Does it cause problems?? Anything else I missed?? Compression feels normal when you pull it over and it kicks back when you shut it off.

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Comments (10)

echoman
16 years ago
Have you installed a new plug and the correct one, gapped right? Did you make sure the carb was real clean, did you blow it out with compressed air when you had it apart? Is the fuel tank clean? You may be getting pieces of crud in the carb from the tank. Seen that happen. Could have a faulty coil as well. Are you the original owner of the mower, and has anything been replaced since you've had it, like the coil, carb overhauls,etc? The upper seal can go bad by not near as frequently as the lowers due to the extra heat and debris in that area. Just keep pluckin' away at it, and eliminate the possibilties by checking or replacing causes. Seems you're on the right track with trouble shooting.
rdaystrom
16 years ago
Replace the needle and seat in the carb.
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Exactly what odf said. This means taking off the whole muffler assembly and cleaning out the carbon plus cleaning the cylinder exhaust ports. You have to be very careful there not to scratch the piston. This is supposed to be annual maintenance. You can reduce carbon formation by the use of certain oils/additives and making sure it is not running rich. Just adding Marvel Mystery Oil to your 2-cycle mix will go a long way in keeping the entire fuel system and engine clean.
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Gosh Arden, I'm sorry you are still having problems with this. You say the seals are good. The carb has been rebuilt, the exhaust ports are clean. How is the compression on the engine? With your finger over the spark plug hole you should feel quite a bit of resistance when you turn the engine over. If you have a compression guage it should read between 80-100psi cold after a few good pulls. If the compression is low it could be the rings are worn down and need replaced or the cylinder is scratched, or the rings are stuck in their grooves causing a loss of compression. Also, is their any oil leaking around the crankcase halves or under or on top the seal areas? Is the carb warped on the flange mount? It should be flush with the manifold. (don't overtighten the carb screws either) How do the reed valves look? check in there with a flashlight and be sure nothing is lodged between reed and manifold. (like a piece of grass etc) Let us know. Neal
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Thanks for the responses. I did set the float level according to the manual and took apart and cleaned out the muffler underneath the deck. I also cleaned and re-oiled the foam air filter. I may not have used enough oil on the filter, but it's not clear that this would cause it run rich? I also cleaned and regapped the spark plug. I didn't check to see that the new float needle and seat were completely shutting off the gas flow if left to sit for a long time. It's not impossible that air was still seeping into the float chamber through the gasket, but I have my doubts since leveling out the ears on the float bowl seemed to produce a good mating of the surfaces. Jim
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echoman
16 years ago
Second that. I figured you would have since you had the carb apart and had changed the float. Make sure you do this.
frank-d
Original Author
16 years ago
The muffler seems to have a lot of carbon inside. Can you clean it out? How?

Frank-d
walt2002
16 years ago
Have a nice charcoal cookout then throw the muffler in the charcoal afterwards and leave it until next day or when it is cold. Tap out remains.

OR you could try running a few tanks of gas with Sea Foam additive added.

Walt Conner
indy452
16 years ago
I clean all my mufflers with a turkey fryer base. I just crank on the flame and put the muffler on and turn it frequently with a long handled pair of tongs till it stops smoking.

I've cleaned lots of "F" series mufflers and a couple D-400 and a couple D-600 series mufflers. The "V" series I don't do because of quality issues and I don't mess with duraforce engines for several reasons although I'll bet they could be cleaned this way because they are aluminum.

I was always afraid to try this but I did a couple of years ago and I'm glad I did because it works great. It burns all the carbon out and cleans without chemicals and too much elbow grease. Just remember to be careful not to scratch the D series aluminum plates and muffler. And they won't melt either when you turn often.

You have a "F" series so the metal donut muffler will be O.K. to "Cook". Good luck.

Neal
johnuch
16 years ago
has anyone just tried using a gas propane torch on it. another words will that burn the carbon off too, directly on muff.
echoman
16 years ago
Took an aceytelene torch to a v-series(steel) this morning-clean as new! Propane will burn hot enough to tackle the job. Go for it.
frank-d
Original Author
16 years ago
Well, I took my propane torch and baked the muffler, then I tapped it and a jot of carbon came out. I checked it with an air hose, and it seemed clear. When I started the mower, it was LEAN!!!!! I fattened it up and now the power has returned. The muffler appears to be most of the problem I had.

Thanks
indy452
16 years ago
Cool! We Like a success story once and awhile.

I presume you checked the exhaust ports also?

Neal

Lawn Boy 8238AE Running rich

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Lawn Boy 8238AE Running rich

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