Small engine help.

My cousin has a go cart that needed to to be fixed...not running. It has a 3.5HP Tecumseh engine in it. I knew it had been sitting for a while so my thought was stale gas and a gunked up carb. I Went ahead and drained and rinsed out the gas tank, blew out the fuel lines, and rebuilt the carb with a Tecumseh rebuild kit. He said the spark plug was recently replaced and it threw good spark so i cleaned it, re-gapped it and put it back in. The darn thing would not start. It can get it to fire if i spray carb cleaner down the carb but it wont stay running at all. I reset the governer as per Tecumseh spec and the linkages are all right.

I tried EVERYTHING and it wont run. At all.

I did a compression check and got 51psi. From some brief google-ing that appears to be way too low and in the "engine is toast" range.

Thoughts?

Stop fighting it ;)

http://www.harborfreight.com/65-hp-212cc-ohv-horizontal-shaft-gas-engine-69727.html

Had a similar issue with the engine in the cart I built my niece, just never ran right, gave in and tossed the HF engine at it, worked fine. Check the shaft size, you may need a new clutch assembly if your current motor doesn't have the same shaft size.

Change the plug, put a couple tablespoons of oil in the cylinder. Probably a hung valve or really dry rings giving that low number.

It could be that there's a compression release system, so cranking pressures might be really low, but running pressures are higher. Just food for thought.

Did you make sure the float isn't holed? If the float is off even a little bit the needle setting will be toast and she won't start/stay running. Did you get the needle seat back in all the way? They have to be pressed in pretty far. I say go through the carb one more time and do a quick sand on the flywheel pickup to insure that you truly are getting a full spark to the plug.

If it runs on starter fluid, then it is not getting gas. Find out why.

• Remove the float bowl.

• The long hollow bolt that retains the float bowl may have a very small hole near the bottom. This is a jet and it's generally clogged. Clear it w/ a bit of guitar string.

Also, easiest way to test compression on the old flathead engines is the grab the flywheel and throw it against the compression stroke, if it bounces back, its good enough.

If it's not overhead valve then just pull the head and check for a stuck/rust valve. If it's overhead valve then do the same thing, just suffer a little more along the way. Take that baby apart, post pictures, have some fun with it.

Kenny_McCormic wrote: Change the plug, put a couple tablespoons of oil in the cylinder. Probably a hung valve or really dry rings giving that low number.

Tried the oil trick already last week.

I had a known good test plug and still nothing.

tpwalsh wrote: It could be that there's a compression release system, so cranking pressures might be really low, but running pressures are higher. Just food for thought.

No compression release system that i am aware of.

When i rebuilt the carb i put in a new bowl so thats no the case. Carb appears to be working.

My thought is that it will run on carb cleaner because its being forced in there. Highly volitile and lots of it. Anything will light that off. The reason that the carb is not making it run is because the engine does not have enough "suck" to fuel itself.

Maybe i typed that out wrong, it was tricky to go from my head to words.

Take the engine off and build a pulse jet for it.

Not the bowl, the jet. The large bolt like thing holding the bowl on is the main jet. At least on some of them. If you have that kind, look at the holes in the bottom and through the middle. Blow them all out. I've been battling this problem with my chipper/shredder. Old gas in the tank made varnish that wouldn't be flushed out. It would run for a little while, then stop and I'd have to clean out the holes in the jet plug thing, then run some more. I finally put a proper fuel filter in the line and it's been OK since.

Pushrod or flathead? Pull the valvecover/flathead and see if a valve isn't shutting all the way.

i ultrasonic-ed the carb / bits when i cleaned it so although it could still be an issue i guess i dont think its the culprit. Still though at this point ill investigate

under the carb is a cover / baffel held by two #6 screws. remove it there you will see the lifters and the valves turn motor over slowly and watch the lifters check the clearances.
most stock cams do have a compresion releif built in so called easy spin its a few deg of low lift to bleed of static comprestion. at 1000 or more rpm theres little to know time for rev flow.

Also make sure there's gas in the bowl when you take it off.

you can try this old trick too to see if it carb / low compression. Spray the carb cleaning in the carb. Now take you propane torch with gas flowing but not lit flow so you just feel it when held an inch off your cheek place it in the carb and start it if it will idle on the propane let it run 5-10 minutes. shut off and try on fuel only if it runs it was stick rings or crap on the valve seat. if it will not refire rings are shoot or carb is messed up bad

HAIRFIRE FTW

I'm still at carb first. Good carb soak, poke out orifices w/ welders tip cleaner, blow out w/ compressed air. Run inline fuel filter like the Dr said.

I chased a carburetor problem for most of an autocross season in my RX-7. Rebuilds, regulator, float adjustments, the works. Some of them several times. I even cleaned and gaped the plugs and changed wires. Checked the spark several times. I could not get rid of a off idle stumble. It drove me crazy.

Change the plug. Just because it throws a spark doesn't mean it's actually good. Sometimes they will fire properly until they have to do it under compression. Plugs are cheap and easy. That's the first thing I try now.

Tecumsehs are hard starting bitches, btw.

In reply to Appleseed:

Any of the ones I touched started pretty easy, not Honda or well tuned pre EPA Briggs easy but within 3 pulls hot or cold.

Should have added "based on my own experience."

Have you priced a new carb? You might be surprised some are cheap. After I have changed the carb and the engine is still difficult to start. The valves need adjusted.