Upper and lower crank to bushing clearance?

[jim mcclymont]

What is to much clearance? and how does the motor behave if to much clearance

[joecb]

Jim, what motor are you dealing with?

Joe B

[jim mcclymont]

1919 Liberty single has a total of .008 on upper didn’t check lower, one more important than the other?

[joecb]

The general rule for plain bearings is about one and a quarter thousands (.0013) of an inch for every inch of journal diameter. Your bearing is obviously worn well beyond new condition. The question, what is your intended use? The bearing issue aside, will the motor run as it is? if so the best plan may be to just live with it, unless you intend a major “like new” restoration. The extra play in the shaft may affect your ignition point gap, but again may not.

Joe B

[jim mcclymont]

Thank you Joe, point contact created by spring loaded contact,good consistent spark, just trying to get it to run, good fuel delivery, perhaps too much sometimes. Motor just farts. Will re bush upper and lower once I find a source.Will keep you posted.Thanks again,Happy new year

[joecb]

With worn bearings crankcase compression / suction could be a concern. When turning the engine over, do you hear the poppet valve opening ( chattering) , if so, all should be good to go. Be sure and use enough oil. I like 8 to one mix.

Joe

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