MF 35 strange miss

I"ve been working on a 35 with the Z-134 gas engine. Ignition parts are all new and the carb has been refreshed, but it still has a bad random miss. What is odd is that it seems to go away while under a load, either brush hogging or box blading. Sure would like to get it running right even at idle, but not sure what to try next. Would you spring for a new carburetor or swap the points/condenser with the new electronic replacements? One local mechanic believes the shaft might be badly worn in the carb, causing an irratic air flow. Any ideas?

Thanks,
Mike Johnston

Thanks again

Gerald J.

Just a bit rich on the idle or a bit lean it will stumble once in a while. And do the same if the float level is a bit high or low. Won't run rough all the time.

Trottle shaft bushings do wear. Sometimes repair bushings can be found (bronze or oil lite even in the good hardware store) and the worn openings opened up and the bushings pressed in, when the carburetor didn't have bushings originally.

A distributor with many hours can have worn bearings and give inconsistent timing too. Check the point gap while pushing the cam toward the points wiper block and then while pushing the cam the opposite direction. To account for shaft wear, do that on all four cam lobes.

But I'd go for idle just a bit away from the optimum mixture. The presets in the manual are just close enough to make it run so it can be tuned properly. And to adjust the carburetor you need to overcome the corrections from the governor or you will be lead astray going for engine speed alone. You can often adjust for minimum throttle opening with the governor working as an alternative.

Gerald J.

You can get that carb shaft rebored and bushed on your old carb if you think it's sucking air.
However, at today's shop prices that may not be cost effective.

I also got a new distributor, top shaft bearing was worn and would let the point gap change. That helped a lot, move the distributor shaft back and forth on yours and see how much play you have.

could be you have a bare wire somewhere and it shorts out sometimes, have seen that on a old D14 allis I had once.

Keep working on it, do you have a good quality timing light so you are sure the timing is correct.

I use champion D-21 plugs

Do you have a ground engaging tool, like plow or ripper, etc: When you get engine set so that when plow goes in ground and you give it fuel and it takes the fuel pulls nice and smooth. you have got it.

Also note: when you are trying to put the fine tune on it you need the engine warm, I do not like to tune a cold engine.

Gerald J.