4hp Tecumseh wont run! Please help!

[djmct98]

Hello everyone, I'm fairly new to this website and need some help!

Along time ago I picked up a super old Toro 421 snowblower, that has a 4hp tecumseh engine on it. I brought it home and it fired up, but ran very roughly and when it was trying to idle it just kept revving up then dying (surging), and backfired quite a bit. Since then I have cleaned the carb 3 times, and finally rebuilt it. After the rebuild, it started to run better but still couldn't idle very well. I kind of set it to the side for a month or so, and finally tried to get it going again today. I've tried adjusting the idle jet, and fuel mixture jet, and it will idle but only if its on choke. If it's switched to off choke, it runs for a second, then dies right out. It has plenty off compression and new clean oil. It has no air filter since it came off a snowblower. This engine is giving me a headache!

Maybe my valves need cleaning/lapping??

Any suggestions or help would be greatly appreciated!

 

[kendelrk]

go back into the carb and make sure you poked out the holes in the main jet with a wire from like a wire brush, or a stripped bread tie, sounds like it may be plugged. ones thing for sure is the adjustments arent going to be correct if this is the problem, as its running to lean.

 

[djmct98]

go back into the carb and make sure you poked out the holes in the main jet with a wire from like a wire brush, or a stripped bread tie, sounds like it may be plugged. ones thing for sure is the adjustments arent going to be correct if this is the problem, as its running to lean.

I made sure those jet holes were clean of any dirt etc. The engine still has the same problem. Thanks for the suggestion though.

Do unclean or poorly seated valves ever cause problems like this?
Anyway tomorrow I might swap the carburetor for another and see what happens!

 

[landuse]

I still think it is the carb that is the problem here. You could maybe check that all the carb to engine gaskets are good and that there are no cracks. Air getting into the engine through bad gaskets could also cause problems.

To check this, you can start the engine and then spray engine starter around the gasket area. If the engine surges a bit, you know that some of it got sucked in past the gasket.

 

[ak99]

Poorly seated valves can be a contributor to backfiring, however running lean can also cause a backfire.

From what you have described this definitely sounds like a fuel related problem as others have said.

 

[djmct98]

I still think it is the carb that is the problem here. You could maybe check that all the carb to engine gaskets are good and that there are no cracks. Air getting into the engine through bad gaskets could also cause problems.

To check this, you can start the engine and then spray engine starter around the gasket area. If the engine surges a bit, you know that some of it got sucked in past the gasket.

Ok thanks for the help, first im going to try a spare carb that already works, then check my gaskets. The engine is so old so eventually I will anyway be doing a full rebuild.