129 K-301 OVERHAUL PROBLEM

[dfiehtner]

So I replaced the rod, piston, and rings and when I try to start it, it wants to "kick back"; blows
the air/fuel mixture back out the carb. With a shot of starter fluid, it starts, putt putt putt and then runs normal at all throttle speeds. What is wrong? Is there a "release valve" or something STUCK? Points gap has been set at both .020 and .017. No change.

 

[jchamberlin]

David, Welcome to the Forum. I would post your question on the Main Forum for the greatest exposure and response. Your 129 certainly qualifies. As for it's Refurbishment or Restoration, we would all love to see pictures, hint, hint.

Regarding your current issue, logically, the only way the engine could blow air/fuel mixture back out through the carburetor is if the intake valve is open on the compression or exhaust strokes. At least two things can cause this to happen (1) a bent or sticking intake valve, or (2) incorrect valve timing. The valve timing can only be off if the cam gear hasn't been lined up with the crank gear correctly. The fact that the motor eventually starts and "runs normally" would favor the first cause; however you didn't say how well the engine worked when it ran. If I remember correctly, retarding the valve timing should move the torque curve up and advancing the valve timing should bring the torque curve down. So if you have more low-end power than normal, then the valve timing is advanced; if you have more high-end power than normal, then your valve timing is retarded. You would need to disassemble the motor to check and/or correct the valve timing. A sticking intake valve may respond to new oil or an additive like Marvel Mystery Oil in gas and/or oil or other varnish-removing substance added in the same places. I have had great luck with the ash-free oil available from Case IH or MTD.

It seems to me this problem has come up before. I'm thinking Donald Tanner described it as symptom of a problem he was having. We thought he had a timing issue, but it turned out to be a leaking float in the carburetor. But my memory may be playing tricks on me.

Again, you're likely to get a better response from more knowledgeable and experienced people on the Main Forum. Good Luck.