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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 12592
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a Tecumseh hs40 on rupp minibike, Runs good when

Customer Question

I have a Tecumseh hs40 on rupp minibike, Runs good when cold, Start's missing once it warm's up. Found hair line crack next to key way on flywheel. Would that be making it fail, Or could it be the coil breaking down, I would be happy if it were the coil, Can not find a flywheel any where. Part #32517. Any Hope For Me. Thank You So Much. Gary.
Submitted: 9 months ago.
Category: Small Engine
Expert:  JohnF2015 replied 9 months ago.

Hi, my name is***** will be assisting you.

How long does the engine run before it starts to act up and miss? I doubt that the crack is a problem. My thought is the ignition system, possibly points and condenser on a older engine or the ignition coil. If you can provide the model and spec or type from the engine tag I can better assist you with that.

Customer: replied 9 months ago.
minibike sat for 20 plus years, replaced carb w/ new OEM. Ran decent at first, then started missing bad. With in 1 to 2 minute's, start's missing and smokes. Model # ***** - 553300 the last 0 might be a, C (not sure) Also does the notch in the flywheel key face the engine or the flywheel. Thank you John for all your help.
Expert:  JohnF2015 replied 9 months ago.

Notch on key will face the flywheel. The last 0 is in fact a C.

Based on your provided information this sounds like a fuel related issue rather than an ignition problem. Can you tell me what the part number was for the new carburetor that you put on? I am wondering if it is the correct carburetor. Is the new carburetor adjustable, maybe try adjusting the bottom jet by turning it in just a little bit and see how the engine runs.

Customer: replied 9 months ago.
Carburetor p/n:631918, there is one adjustment screw on side of carb and one on bottom of float bowl.
Expert:  JohnF2015 replied 9 months ago.

I would try to turn the bottom one in about an 1/8 of a turn and see what happens.

Expert:  JohnF2015 replied 9 months ago.

Your engine by model and spec shows that it should have a diaphragm style carburetor on it not a float style. The diaphragm style is not available anymore. How did you come up with the part number for the float style? Who sold it to you? This is the most likely problem, the carburetor is not the right one for this engine. You could possibly still make it work by adjusting it but don't be surprised if it still doesn't run correctly and that it cuts out or floods itself when you are riding in rough areas.