A smooth running Cub engine

[Jackman]

I'm trying to get my Cub to run smooth , its not smooth has flutter and slight hesitation at idle and high throttle I've got good compression and recent valve adjustment and new repo carb with 6 different main jets to choose from, my governor is free and set to spec , timing is set with a light, I have an electronic ignition with 12 volt conversion , clean air filter and the block vent is clear, all that said it does run good but its not quite right... Any suggestions?

[tst]

when you switch to electronic you are suppose to use suppression wires as copper and electronics to not play well together, does the advance work for the timing ? you can watch the timing marking with a timing light to make sure, what were the compression #s ? can do a cylinder leak down test to be sure

[Jackman]

Ah I didn't consider the plug wires , I'll have to swap wires currently they are TM Tractor original copper core type wire. That would be awesome if the correct wires solved the problem. The compression was good I don't remember the numbers I tested last year , the advance is free I took it a part for cleaning all looked good .

[tst]

verify the timing advances, use a timing light, decent compression is 100 lbs plus, all cylinders in theory within 5 lbs of each other, most engines when I rebuild them are 140-150 lbs

[Eugene]

I'm trying to get my Cub to run smooth, it's not smooth has flutter and slight hesitation at idle and high throttle.

Is the flutter and slight hesitation all the time or just when you move the throttle to change engine rpms?

If it's all the time, I'm thinking it's within the mechanicals, wear, of the distributor.

An engine oscilloscope would/might indicate the problem.

[Jackman]

Engine seems fine when moving throttle up or down , at idle and high RPM's its got the flutter and slight hesitation. I'm going to look for the suppression wires first it could help a lot I think...

[tst]

hesitation more of a sign for timing issues

[Jackman]

Wires on order will check timing again when the wires arrive. Thanks!

[Clemsonfor]

hesitation more of a sign for timing issues

Could be a mid adjusted carburetor too.

[Jackman]

hesitation more of a sign for timing issues

Could be a mid adjusted carburetor too.

I think that too and have swapped carbs I have two new import carbs and one original carb and two TM tractor main jets ,I'm using the best working main and import carb with the air screw 1 and 1/2 turns out ,Air screw seems same no matter where its set. air filter has had a good wash out not long ago.

[Jackman]

Video running with suppression wires, seems better but I’ve heard smoother running Cubs . Any opinions?