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I repair lawnmowers and most lawncare equipment and stuff as a side hobby/business.

Usually i can get them going good but this one has me stumped.

Its a 10-12 year old 21" craftsman 6hp pushmower self propelled that the owner has always ran it on non ethanol gasoline. Hes always had another guy make sure its tip top shape each spring (change oil when it starts to look black, plenty of new plugs, blades sharpened etc)

Well the owner recently put E10 in it and after a mow or two of his smallish suburbia yard it would get very hard to start. Prime it 3 times pull the cord will fire right up run smooth for a second then start sputtering and die. Do that routine about 4-5 times it will then start revving up and down then after it warms up a bit after 3-5 minutes it will smooth right out full speed no smoke plenty of power and will be fine till it runs outa gas or he stops it.

My first thoughts was the ethanol released some varnish from the gas and clogged some crap up.

Ive used 2 full cans of spray carb cleaner on the carb, float, needle, bowl, and just about everything else. I couldn't figure it out.

The owner all last season ran regular non ethanol gas in it and it slowly got better to this spring it did its start stall thing once then smoothed right out so regular gas is slowly fixing it...

Ive never seen or heard anything like this before.

Oh before he put e10 in it it started first pull and ran great.

also i forgot to add is once it starts stumbling and stalling if you press the primer button it will perk right up so its clearly fuel related.

A friend of mine was looking into running his truck on e85 (yes e85) He's a farmer, and was gonna make his own ethanol, and make the 85/15 blend.

But he said that any plastic in the system must be compatible with ethanol, or it will eat it.

Perhaps the ethanol wrecked something plastic inside the carb ?

He said he already ran his lawncare equipment on e85....but he had to rebuild the carbs to handle it. He ran his diesel tractors on biodiesel, too. Fuel costs really had him mad....the first time they spiked a few years back.

I've been screwing with these things since the '50's.
If the guy took as good care of it as you say, he probably drained the gas or, at least, put Stabil in the tank for the winter. I doubt that varnish is the problem. If fact, the only time I've had a problem with varnish is when a implement was put away and left long enough for the gas in the tank and carb to dry out (years).

3 things I can think of:

It is old enough to have a condenser in the ignition system. If these short out, the engine will idle but, when you try to accelerate it will stall. Need to pull the flywheel to get at it. They're cheap, Don't try to diagnose it, just put a new one in and throw the old one away.

I've seen older carbs with a rubber diaphragm under a rectangular cover. They act as a fuel pump and when they crack, the engine will not run well or not at all. 10-12 years is about as long as they last.

Check the carb to engine mounting bolts and gasket.

Good luck, Jim

jimbir said:

I've been screwing with these things since the '50's.
If the guy took as good care of it as you say, he probably drained the gas or, at least, put Stabil in the tank for the winter. I doubt that varnish is the problem. If fact, the only time I've had a problem with varnish is when a implement was put away and left long enough for the gas in the tank and carb to dry out (years).

3 things I can think of:

It is old enough to have a condenser in the ignition system. If these short out, the engine will idle but, when you try to accelerate it will stall. Need to pull the flywheel to get at it. They're cheap, Don't try to diagnose it, just put a new one in and throw the old one away.

I've seen older carbs with a rubber diaphragm under a rectangular cover. They act as a fuel pump and when they crack, the engine will not run well or not at all. 10-12 years is about as long as they last.

Check the carb to engine mounting bolts and gasket.

Good luck, Jim

Click to expand...

He said it was only 10-12 years old......that'd make it around a 1998 at oldest. They still had condensers? Thought Magnetron did away with that in the 80's? Also, I believe a 6 horse pushmower would have a bowl carb...isn't what you're talking about (diaphragm) for a 3.5 horse, or a rider with a rear tank? A push mower of this type would be gravity - fed.

BTW, welcome to LMF, fellow New Yorker, and Snapper owner! :thumbsup:

oh and i replaced the carb to engine gasket and the bolts are tight.

Everyone else i know has always run E10 in thier small engine stuff and its been fine. we have for prolly 30 years now on all sorts and ages of engines with no fuel related problems.

The guy doesn't know much if anything about how an engine runs so he would just leave whatever last years gas in it and then fire it up in the spring. Its always kept in a garage so no weather can get to it either.

it does the rpm loping like the carb is maladjusted but if it were that would not get better the longer its ran would it?

there is also a new sparkplug on it too.

There is (ever so slightly) less energy in E10 than there is in gasoline... If the carb is adjusted almost too lean to begin with ... the slight reduction "could" make it a bit off...
This is quite unexpected but you should be able to richen up the mix where it will run with either...
:smile:KennyV

Have you run a compression test? Simplest is usually the best answer, rings are not designed to compress that fuel. Premature piston ring wear is a what I'd say. Compression raises after it gets warm enough for it to run correctly. Any compression less that 90psi "cold & dry" will do this.

I really like the compression test approach. It's very hard to diagnose these problems by remote control.

Interesting, I never thought of compression being the culprit...

yea ill hook up my compression tester to it and see what we get. I always thought small engines were good enough if it could blow your thumb off the sparkplug hole when pulled...

jimbir said:

I really like the compression test approach. It's very hard to diagnose these problems by remote control.

Click to expand...

I agree with the above. Rarely do I have one I can't seem to repair but there are those few. My most recent problem child has been with a stuck valve problem. However, I enjoy the challenge most days. Anyone have any experience with teejet spray nozzles ?