Kohler backfires

[DCPULLER]

Hi, I'm working on a Sears Craftsman garden tractor with a 22.5 hp OHV engine and I have a problem. At first the engine wouldn't run without having the choke pulled out some. It would be surging or hunting on the govonor. Cleaned the carb and ran fine figuring the idle passages were partially plugged. There was some varnish in carb, after cleaning it ran great. Throttle responce good from idle to WOT.Drove around no problem. Went to mow and when I engaged the mower the engine sounde labored and the more I mowed it started backfiring which it did also before I cleaned the carb. It gets worse the more I mow. Any suggestions? Thanks, Dave S

 

[IA Roy]

Check the points and check with a timing light. It is very likely an ignition problem.

 

[IH2444]

Yes check the ignition first. if it is ok then it is probably a valve.

 

[Larry Dorsey]

OHV Kohlers do not have points. Take a .012" tag wire and open up the transfer ports in the bore of your carburetor.This is a common problem on later model Kohlers.

 

[Kentb of SWMO]

How old is this engine? Sometime, when these newer engine get some hours on them the will not run correctly at the lean setting from the factory. You need to rich-en the mixture. The only way to do this is to drill out the fixed main jet. You could also have a thin film of varnish still on the the fuel passage through the main jet that is restricting the amount of fuel the engine is getting causing the lean fuel/backfire problem. I use small number series drills to clean and if I have to enlarge the main jet in today's fixed fuel mixture carbs.

Kent

 

[Trailer Trash Tractors]

I would check for vacuum leaks, squirt running engine with water, if engine speeds up, there's the leak. A plant watering can works great, you only need a few drops at a time. I agree with other posters, could be dirt / restrictions in fuel system, low float ? Backfiring is usually too lean a mixture.