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Collection, Preservation and Display of Old Lawn Mowers

Suffolk Colt/Super Punch 25A engine vibration.

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This engine was difficult to start and vibrated a lot. The carb was worn though.

I have completely dismantled and cleaned it up and reground and gapped the valves.

adjusted the timing,new points, plug  and a different carb

It still vibrates and behaves erratically but there is an improvement.

My question is both carbs have the washer for needle seating missing so the the seating rests against the counter bore of the carb body.

- Could this be the problem?

Forums

wristpin Fri, 19/08/2016

I've just had a look at a carb and can't make up my mind whether it has a washer or not. Certainly not going to upset things but trying to hook out a washer that doesn't exist! If there should be one and yours is missing the only effect will be a slightly raised fuel level with a small  possibility of flooding. If there should be a soft alloy washer it would probably be to seat the jet and stop fuel leaking around it.

I would think that you need to look elsewhere for the cause of the vibration .  I suggest that you remove the centrifugal clutch from the crank shaft and try the engine without it . If that solves the problem it points to out of balance in the centrifugal clutch or the drive line . Not sure what the effect of one free and one seized clutch shoe would be.  If no improvement , it's either "just  how it is" or possibly an out of balance flywheel ; not that I've ever come across that either even when there's been a couple of fins broken off.

goodgrass Fri, 19/08/2016

The engine is not attached to the mower but screwed to a wooden plank.

It seems  to run ok for a while then starts vibrating a bit like a compactor as it warms up.

It's running better since i replaced the dodgy throttle spring and governor blade donated from another engine.

wristpin Fri, 19/08/2016

You don't say whether or not the plank is anchored to something reasonably substantial: try clamping it to the bench or something with a bit of mass to absorb the natural vibration frequencies and then run at different speeds to see if it goes through different vibration periods. Could be that when set up on its own chassis it is ok.

goodgrass Fri, 26/08/2016

There is a washer there, which may be alloy. I was expecting to see a fiber or rubber washer.

Seems more stable with a different carb.

The plank is not clamped, I just put foot on it