Cub still not running well...

[BearGap]

Thanks for the several suggestions on how to fix the old Cub. Here"s what I have done. Recall it was running fine until taken to a shop to replace a busted throwout bearing. Since returning it doesn"t run well enough to be used for anything:

1. Pulled and inspected the plugs - all had a grayish deposit around the electrode, but looked clean, dry, and free of oil. The distributor cap and rotor are new as are all the plug wires. The coil, points and both condensors were replaced with the plugs last Spring and it ran fine through the summer.

2. Verified firing order as 1,3,4,2 with 1 being at the 1:00 position looking at the distributor

3. Pulled the carb apart and inspected it. No dirt in the inlet screen and nothing observed inside. Cleaned with some spray carb cleaner to verify openings were clear. Loosened the main metering jet from outside and verified fuel is flowing out the drip hole.

4. Checked the air cleaner, which was a little low on oil but otherwise OK.

5. Started and observed that after warming up a bit it will run very smoothly, but only at a low idle. Advancing the throttle immediately results in (brrp brrp pop pop brrp) missing and poor running, almost killing the engine. Advancing slowly seems to allow it to speed up better, but still seems to miss a bit periodically or a lot under even a light load.

6. Adjustments to the idle screw have little effect, so I left it about 1 1/2 turns unscrewed.

7. Pulled the sediment bowl and everything appears clean. Reinstalled it and opened the valve, and pulled the fuel line off the carb and verified fuel runs freely through the hose.

Could this be a problem with the governor? Is there an advance mechanism in that housing? This has a 12v conversion and I have never touched the timing or opened the governor in 20 years...just set point gaps by feeler gauge when doing a tune up. It almost always is used at just about full throttle and had been running well this summer, with an occasional stumble when pulling a load and turning uphill while the regulator catches up. I appreciate the advice as it is not usable at the moment.
 

[glennster]

if it just had a throw out bearing put in, then it was probably split to do it. i'd would re-check all the wiring to see if something is pulled loose or pinched, especially from the ignition switch to the coil. if its a 12v, check the ballast resistor for damage. also check the distributor where the small wire from the coil goes thru the housing to the points. there is a little bakelite type grommet in there, and if its cracked, it could be shorting out. i am leaning toward an ignition/electrical problem. posibly condenser or coil. also, check the distributor shaft for side to side movement, it may have worn bushings in there. rotate the engine till the points close, then wiggle shaft side to side to see if there is enough slop to vary the point gap.
 

[old]

Make sure you have a good blue/white spark at all plugs that will jump a 1/4 inch gap or more. Next pull the carb drain plug and make sure you have a good steady flow of gas for a few minutes. Catch to look for water/dirt etc. Next since this is a cub and most likely does not have an adjustable main jet pull the cap off that covers the main jet and make sure you have a good steady flow of gas there. Any of all of those can cause that long with what Glen said
 

[S2710]

BIL has a little ford and it was doing the same thing and we changed the condenser and it runs like a top. The condenser that we took out was brand new and the one we put in to make it run right was used.

Bob
 

[old]

Ya now days I do point an plugs but I do not replace the condenser since you stand a 75% chance a new condenser is going to be bad or only last a short time
 

[Brett Helmkamp]

Did you try turning dist to advance timing? Spark plugs can make a huge difference. Keep away from the Champions anymore. Maybe the timing is just off a little. Just a thought