MTD 139cc Mower - RPMs Dropping Randomly

[DianeW13]

I have an MTD 139cc lawn mower, model # 11A-54MB029, and engine model # is 1P65M0. It died and did not start again after hitting a stump. I re-gapped the ignition module, I adjusted the valve clearance which were off (.004 intake, .006 exhaust), and put on a new plug. The flywheel and key are both intact without issue. It fires up first pull now. It runs strong, then 15-20 seconds in, it starts dying slowly, and RPM's drop significantly. I can hold the governor, and it will run and even out. Any ideas what it could be? Weak coil? Governor messed up?

 

[Jonb62]

Check to see if it is running too rich. I had a stuck float that did that. Good luck.

 

[sgkent]

Check to be sure that the blade and blade holder did not shear their key.

 

[StarTech]

If you are able to hold the throttle vane steady and the engine smooths out and keeps the same rpm then governor static adjustment is probably needing to be done. So far I only seen less than a hand full of these engines an all had carburetor from sitting too long so Not familiar enough with them to the procedure as the service manual doesn't this adjustment very well at all.

Just note there can be other damage as a stump strike is very hard on an operating engine especially at full throttle. Surprised that the flywheel key didn't shear.

 

[artemjemmy]

I have an MTD 139cc lawn mower, model # 11A-54MB029, and engine model # is 1P65M0. It died and did not start again after hitting a stump. I re-gapped the ignition module, I adjusted the valve clearance which were off (.004 intake, .006 exhaust), and put on a new plug. The flywheel and key are both intact without issue. It fires up first pull now. It runs strong, then 15-20 seconds in, it starts dying slowly, and RPM's drop significantly. I can hold the governor, and it will run and even out. Any ideas what it could be? Weak coil? Governor messed up?

Possibly something with the auto choke setup? Not exactly sure how the automatic choke works on this Chinese engine, but it may have to do with the governor arm position. Make sure the choke is staying wide open. A governor problem should never cause the engine to "die out". As always, a video of the problem will always help.