We picked up a go-kart powered with a Tecumseh 10-hp snowblower engine, best I can tell it is a type HMSK100. I can't properly adjust the mixture screws. I can get the engine to run, but it blows smoke, hunts a bit, and surges from time to time. I have no idea how to set the idle or main mix. It will run, but as soon as the throttle (gas pedal) is depressed, it dies. So that I don't completely destroy this engine, can someone help give me a baseline start on adjustment settings for the idle speed screw, idle mixture screw, and high speed screw (under the carb bowl)? Thanks in advance.

 

Sounds like the low speed mixture screw is set a bit lean(screwed in too much). A common symptom of lean running is the surging. With the engine at idle, turn the low speed mixture screw out until the engine runs at it's smoothest point. Then run the engine wide at full throttle, and do the same with the high speed mixture screw. As for the idle speed screw, adjust it so that the engine idles at a decent speed(just go by ear for this one). Just so the clutch doesn't start enguaging when it's at idle.

 

Sounds a lot like it might need cleaning. Have you cleaned the carb yet?

 

Are you using an air filter? Tecumseh designed the SK models to run without an air filter. Most snow application engines are designed this way due to there being very little (if any) dust created while working in the snow. This may account for the engine running rich and surging.

 

Thanks for the tips!

1. From full closed position, I turned the low speed mix and high speed mix screws out about one full turn and 1-1/2 turns respectively. That helped a little, but it's still blowing smoke.

2. Can you clarify if surging is caused by too lean or too rich mixture? The answers given conflict..! Seems smoke would be caused by too rich (?)

3. I agree with "Cheese", I think the jets are clogged and a good carb cleaning would help.

Any other suggestions?

Thanks again for your help!!!!

 

BobSabre,

I agree with Cheese about the jet being clogged. The bolt that holds the bowel on, remove and clean the tiny holes at the bottom with carb cleaner and compressed air. These holes can become clogged and prevent good fuel pickup however, if you are getting skipping with black smoke then instead you may need to consider engine placement. If the carb bowel is not aligned properly (vertical) the inlet needle will not seal and cause an over flow into the carb bowel which will induce a flooding (black smoke/skipping condition)?

Surging can be caused by either rich or lean condition. A plugged jet will cause both conditions which in turn can cause you to tear your hair out twisting screws until you clean the clogged jet.....

God Bless,
Dave237

 

Surging can be caused by having the mixture set too rich. By running an air filter on a carb jetted to run no filter, the engine will be starving for air thus running too rich, bogging down, blowing smoke and surging at too low of an RPM. Try to run it without an air filter and see if there is an improvement.