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Hey guys, new to the forum and would glad to help out with any issues now or the future. I have a slight problem, I work on ATV's and Dirt Bikes full time and rarely ever work on small engines but I took the job because I figured how hard could it be, cant be any different from a Polaris engine just less horsepower and smaller. Well I was wrong this engine has eaten my supper,lol.

This is what I got, Tecumseh Power Sport on a yerf dog go cart I know this is a mower forum but I was hoping someone could help. When I got the engine someone had put mixed gas in the engine causing the valves to stick and the exsaust push rod to bend.

I have replaced both push rods, replaced the valves and set them to .004 gap, replaced the seats, springs etc... Rebuilt the Carb, set the ignition coil to buisness card depth "always worked for me" did a jump the gap test on the spark plug and Im getting fire. But it still will not crank, it wont even stutter. I dont understand I have replaced everything but the engine itself and the carb itself.

Any help to get this thing to crank would be greatly appreciated

Thanks
Matt

Did you clean the jet that is in the nut that holds the carb bowl on.

I set my coil air gap a little closer then you do I just use a peace of paper. I think it should be around 6 thousand a bussness card is a little much.

You need fuel, spark, compression and timing. I would start by squirting a little gas on the air cleaner. The timing is the hardest to check save that for last.

You say you work on engines all the time and you are right this one is no different then a ATV or motorcycle, I also work on them. You just are missing something compression, spark, fuel, and timing and it will run. If you do this for a living you should know how to check each of these things.

reynoldston said:

You say you work on engines all the time and you are right this one is no different then a ATV or motorcycle, I also work on them. You just are missing something compression, spark, fuel, and timing and it will run. If you do this for a living you should know how to check each of these things.

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Wow I didnt know the welcome would be so nice... All I was asking was for help not a smart answer. There is no cam or no timing chain just 2 valves and a piston so no I do not know how to time this engine if it even has timing. It has fuel, it has a spark you would know this if you read my post and it has good compression. With all do respect there is a very big difference in a 700 cc V-Twin water cooled engine with EFI and an oboard computer vrs a 200 cc go cart engine. So yes I have been doing this for 6 years and this is the first small engine that I have ever worked on. Thanks for you help

ILENGINE said:

Did you clean the jet that is in the nut that holds the carb bowl on.

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Yes I replaced it, its getting gas from the carb to the engine. Thanks for your help

reynoldston said:

I set my coil air gap a little closer then you do I just use a peace of paper. I think it should be around 6 thousand a bussness card is a little much.

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No problem will adjust that now, thanks for your help at least there is a few helping people.

originalswampfox said:

You need fuel, spark, compression and timing. I would start by squirting a little gas on the air cleaner. The timing is the hardest to check save that for last.

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I have fuel from the carb to the engine, I have a spark on the plug, the compression is at about 113 psi, how do I check the timing. Thanks for your help

Sorry I didn't mean to make you mad at me. I just thought you would recheck your self. I can go over it with you if you want.. I did this for a living all so and never liked someone telling what to do. Timing isn't much to check just make sure the key is good in the flywheel and Air gap. Does this engine have points and if so that will change your timing if the gap is off. You said compression was good and you did check the plug in the engine under compress witha a spark tester. I check fuel with starting fluid in carb. Sorry about that misunderstanding. :frown:

reynoldston said:

Sorry I didn't mean to make you mad at me. I just thought you would recheck your self. I can go over it with you if you want.. I did this for a living all so and never liked someone telling what to do. Timing isn't much to check just make sure the key is good in the flywheel and Air gap. Does this engine have points and if so that will change your timing if the gap is off. You said compression was good and you did check the plug in the engine under compress witha a spark tester. I check fuel with starting fluid in carb. Sorry about that misunderstanding. :frown:

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I understand I dont like people telling me what to do either when I know what I am talking about but I was asking for help on this forum and giving help and telling someone what to do are two different things, I accept your appologys and I am sorry as well that I took it the wrong way. The flywheel key is good the old one was sheared just a tad bit so I replaced it as well. It doesnt give any kick back like a bad flywheel key would do when you pull the cord. No there are no points in this engine. I just set the gap on the valves and thought that would be it. I did not however check for a spark with the plug in the engine, the compression is about 113 psi does that sound about right? I will check the plug in the engine tomorrow and let you know what I find out. Again I appologize, thanks for you help

Matt

Mat,

No apology necessary, I keep thinking we are missing something. Going back to the beginning when you first got the engine it had a bent push rod. We think the mixed gas caused it. When the rod got bent the valve was probably hit by the piston. The flywheel key was partially sheered. So much for all that bs, to check to make sure everything is in time
1. Take out the plug.
2 roll the engine over by hand until both valves are closed.
3. magnets on the flywheel should be lined up with the coil.
4. use a screw driver or piece of wire and insert in the spark plug hole and make sure the piston is on top dead center. Just roll the flywheel back and forth and see if is all the way up.

Have fun and let us know it is going

I'm not a Power Sport man but I've worked on engines for over 40 yrs and have seen some strange thing happen. Like I said in the beginning somewhere we are overlooking something. Back in the late 60's I did race go-karts, we used 5 hp briggs. My wife finally made me quit, it cost too much money.

No professional mechanic here, just a shadetree with a question and maybe a suggestion or two. Why would you think mixed gas would cause the valves to stick? That seems counter-intuitive to me. I would think the oil in the gas might cause things to be better lubricated, not the other way around. But, I could be wrong.

Also, you asked about timing. There is a cam in this engine, just like every other 4 stroke, but you didn't mention making sure that it is timed correctly. The cam may even be plastic, I have seen a few that were, usually on small B&S engines. I'm thinking the cam may have jumped time when the piston crashed that valve. Also, on the spark issue, it does take more voltage to jump the gap under compression than it does at atmospheric pressure. You measured 113psi compression. While that does sound a little low to me, it should be enough to make the engine run just fine, although it might be a little down on power.

reynoldston said:

I set my coil air gap a little closer then you do I just use a peace of paper. I think it should be around 6 thousand a bussness card is a little much.

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The coil air gap on tecumseh is .0125

Ok update on the power sport.

I tore it back down and checked off everything again.. Lets go down the list

Fire- CHECK
Compression-CHECK
Timing-CHECK
Fuel- NO CHECK

Now the carb is not pumping gas into the head. It has been completely rebuilt but tomorrow I will take it back apart and make sure everything is set right in there also.

mullins87 said:

No professional mechanic here, just a shadetree with a question and maybe a suggestion or two. Why would you think mixed gas would cause the valves to stick? That seems counter-intuitive to me. I would think the oil in the gas might cause things to be better lubricated, not the other way around. But, I could be wrong.

Also, you asked about timing. There is a cam in this engine, just like every other 4 stroke, but you didn't mention making sure that it is timed correctly. The cam may even be plastic, I have seen a few that were, usually on small B&S engines. I'm thinking the cam may have jumped time when the piston crashed that valve. Also, on the spark issue, it does take more voltage to jump the gap under compression than it does at atmospheric pressure. You measured 113psi compression. While that does sound a little low to me, it should be enough to make the engine run just fine, although it might be a little down on power.

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Who ever owned this cart before this man appartly put mixed gas into the tank, either one of us know how long it sat or how much 2 stroke oil was mixed into the gas that the person used. My theory is that the cart sat in the sun outside for a while " maybe a year or more" and it had to be ran with the mixed gas which probably just caused it to smoke alot. The valves had at least 1/8" of sludge on them they had to be beaten out of the head, the only thing that I can figure is that the oil from the gas mix just burnt onto the valves, Causing the valve to stick, shearing the flywheel key a bit and it just all went down hill from there.

If this engine has a cam it must be the size of a marble because I have had it basically tore completely down everything except splitting the caseing, and no cam has been seen. From what I understand and could be wrong but these small tecumseh engines run from around 90-120 psi.

its impossible for a 4 stroke not to have a cam:confused2:.......1/8" of gum?...someone was throwing some weird s@$t into that thing......what are the model/serial numbers on this thing?

except a rotary / wankel of course..........can you take pictures for us?:thumbsup:

I'm wondering what reddragon is wondering....what did the previous owner put in that motor?!?!?! Yes, it does have a cam. A 4 stroke cannot operate without one. Well, not without getting into a really tricked out solenoid controlled valve system. It's gotta be there.