Small engine question (lawnmower)

hi guys today i am getting a snapper commercial lawnmower from a friend of mine and he says its not running.

he said hes replaced the ignition module and fuel tank. he also says that its 10 plus years old.

im thinking that its not running because of the new ethanol in our gasoline. what do you think? where should i start? and no im not going to junk it. i like projects no matter what size.

it has the wisconsin robin air cooled engine if that helps. i cant even find a picture of the darn thing.

It is not as simple as ethanol gas. 10 years old for an air cooled engine is pretty old. If it was used by a lawn service that is very heavy use, several running hours daily 6 days a week.

If the motor isn’t siezed up, check compression. If you have spark and fuel, lack of ignition is likely low compression. These motors have a compression release system to make them easier to turn over when starting. If the compression release is stuck that could be the problem.

check out this web site for all the info on small engines and ethanol problems…

compression release huh? i wonder if thats it. if that is the case should i try starting fluid to help it get going?

If the machine has been sitting unused for a while the carburetor is probably gunked up or corroded, or both.

I recently borrowed a chipper from a friend who had not used it in several years. It needed a new carburetor before it would run.

i hope its not the carb. but taking off the bowl would probably answer our theory right if theres green stuff in it?

If E10 was used in the engine it probably damaged the carburator components. When this happens the carburator will require rebuilding.

When Minnesota tried to mandate in 1992 that all gasoline sold had to have 10% ethanol, and people started using it in their small engines, we started seeing the damage it could do to these older fuel systems. In some cases the fuel system would be damaged in one season of use of the equipment and the fuel system would have to be rebuilt again.

I picked up a lot of free lawn mowers, lawn/garden tractors, outboard motors, snowblowers, etc, from those who got tired of their small engines not running from ethanol damage. I’d just rebuild the fuel systems and resell them.

But here in Minnesota, we have access to gasoline that is ethanol free. And this is what everyone here uses in their small engines with older fuel systems and in their older vehicles.


Three things to check:

Does it have compression?
Does it have spark??
Is it getting fuel??

To check for fuel, dump a TEASPOON of gasoline down the carburetor and see if it will start momentarily…This can be hard to do with an updraft carb… In that case give it a shot of starting fluid in the air intake…

I hate to say “I told all of you this would happen”, but it happened even earlier than I thought it would. We had another post with many threads on a 20 year old Toro snowblower. I predicted we would soon be into lawnmower engines.

I had a Wisconsin engine on a rototiller some years back. I had to replace a broken valve spring to make it run. This was a used engine that I picked up to power the tiller when the original engine gave out.

My attack would be to pull the spark plug out and put my thumb over the spark plug hole to confirm that there is compression. I then check for spark by laying the plug on the cylinder head and pulling the starter. If the engine has compression and spark, I pour a little gasoline (just a little) into the cylinder, turn it over with the plug removed to atomize the gasoline, then put the plug in and see if it hits. If it does and then stops, there is a fuel problem.
If my memory serves me correctly, the Wisconsin engine has the ignition points activated by a rod and are under a cover so that the flywheel doesn’t have to be pulled to set the gap. Wisconsin made a good engine–don’t junk the mower.