Tecumseh 5hp lacks power when warm

[threeputtpar]

A little update again.

Pulled the intake, muffler, and the crankcase breather to inspect the valve clearance. The intake was at .004 and the exhaust was .008, which are both right at spec. Now I'm really stumped. Is it worth the effort to pull the exhaust and increase that clearance to .010 or .012 as long as it's apart?

At this point I have enough of the engine on the garage floor that I might as well pull the head and get a look at the top of the piston and the valve seats. I'm hoping that there is a bit of carbon stuck on the valve or seat that's holding the exhaust valve open a bit, but I'm not holding my breath.

I also picked up an inline ignition test light and I'll hook that up when it's all back together and see if the spark gets weak when it starts to bog down. Maybe the coil is going bad.

2oldtommy - This one actually has the solid state ignition coil which surprised me. I found online that Tecumseh made the switch around 1983, so this must be one of the first model years that didn't have the points and condenser.

 

[Quest]

sounds like you may have to pull the cylinder head to inspect...also, if possible: pull the intake and exhaust valves and inspect the valve seats for erosion (due to stuck carbon or debris).

If all is well, get some lapping compound to lap both intake and exhaust valves.

check cylinder wall for severe scouring and possible broken ring(s)...it's hard to do such inspection while the piston is still in the bore, but do your best anyways.
Q.

 

[threeputtpar]

Final update:

The problem ended up being some kind of gunk inside of the valve guide of the intake valve that was holding up the valve from fully seating. For a rookie, getting the valve and springs out wasn't as hard as I thought it would be. An old body fastener tool that I had for the thumb press in rivets on the last GM product I had worked great in place of the expensive spring compressor. The angle on the head of it makes just enough of a bend to pry up the spring and release it from the cap that it locks in, even though it's hard to see the bend in this picture.



And as long as it was all apart, I cleaned up the exhaust valve and decarboned everything and installed all new gaskets. Now, maybe it will be worth the effort to pull the body apart this summer and sand and primer and paint everything and get it looking nice and new.

This thing really chucks the snow now for only being a 5hp with a shorty exit chute. And now that I've gone through the engine completely, I can be confident that it will be a good machine for the long term.

 

[SOHCman]

Glad to hear you have figured it out! Nothing like bringing an old machine back to life.

 

[AandPDan]

Glad you got it running and it was an easy fix.

 

[wag123]

Originally Posted By: threeputtpar
Final update:
The problem ended up being some kind of gunk inside of the valve guide of the intake valve that was holding up the valve from fully seating.

What that "gunk" was on the intake valve stem and guide, and where it came from is... varnish, from running it on old/bad gas. YOU may not have run it on old gas, but SOMEONE did. I have seen this hundreds of times over the years. For those of you that think you can put something in the gas to fix this problem, you can't. The valve needs to be removed and cleaned. Every year I have seen this sort of thing on lawnmowers in the spring and summer, and when I lived up north, I saw it on snowblowers in the fall and winter. Stabilizer does NOT stop this from happening, it just delays it a little.
The bottom line is this, do not purchase more gas than you will use-up in 3 months, and then USE IT ALL UP! At the end of the season, run the engine out of gas before storing it.

 

[threeputtpar]

Originally Posted By: wag123
Originally Posted By: threeputtpar
Final update:
The problem ended up being some kind of gunk inside of the valve guide of the intake valve that was holding up the valve from fully seating.

What that "gunk" was on the intake valve stem and guide, and where it came from is... varnish, from running it on old/bad gas. YOU may not have run it on old gas, but SOMEONE did. I have seen this hundreds of times over the years. For those of you that think you can put something in the gas to fix this problem, you can't. The valve needs to be removed and cleaned. Every year I have seen this sort of thing on lawnmowers in the spring and summer, and when I lived up north, I saw it on snowblowers in the fall and winter. Stabilizer does NOT stop this from happening, it just delays it a little.
The bottom line is this, do not purchase more gas than you will use-up in 3 months, and then USE IT ALL UP! At the end of the season, run the engine out of gas before storing it.


You are probably right that the former owner used old gas in this poor, neglected machine. They are good family friends of ours, but he has no clue (or interest) in maintaining his equipment. Thus, I have a good pick of OPE projects whenever I want something to tinker with. He actually has 6 2-stroke weed whackers in his shed that have been used and abused. Maybe I'll teach myself the inner workings of the 2-stroke engine this summer.

I volunteered this winter to help him get a Honda 522 track snowblower working for him. Those things are beasts in the snow, and it was sad to see it in such neglected shape. I'm thinking in a couple of years it will be to the point where he gives up on it and I can scoop it up for free.

 

[andyd]

I have 3 or 4 Ariens 24 inchers . All have the cast iron augur drive. the tractors are fine at forty yrs old.The varnish is prolly the killer or the points or something. My struggles with the old Tecumsehs was frustrating me. Thae last one seized up tight. It can be rotated backward, but wont go forward.I quit. Then the snow came and I bought an ergonomic shovel. So I decided to try a new 100$ engine. I want to blow snow,not fiddle with a sick engine. With an online coupon print out for 20% off. , I was out the door for 101$. A 6.5 ,212cc "Chonda" from harbor freight. The pulley swaps perfectly. The engine drops onto the studs,but the studs are too short. The studs are spot welded on the underside. It took an hour to hacksaw them off,center punch the stud. and run a 1/8th bit down. A squirt of oil to keep the bit cool. Then a 3/16, 1/4, 5/16. Hindsight is that if I had used a 9/32 , then I could have tapped for a 5/16 thread. The engine starts so easy with a pull. A few seconds on choke, then a purr. Just for grins. I started it at 9F after a night outside. a pull through to wake up the oil, then an easy pull to life. I have it together enough to blow snow enough to test. It blows snow. I have to modify the chute driver to clear the engine. I think I can do it with a U- joint.

 

[Dean85]

Good to hear you fixed it.