G80CS Crankshaft end float.

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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G80CS Crankshaft end float.

Postby reabow gary » Fri Dec 17, 2010 10:52 am

The minimum end float specified in the AMC manual is 0.012inches.Is there a maximum specified anywhere?

The measured end float on my 1958 G80CS is 0.030inches.Is this too much, and will it affect the oil pump drive?

Appreciated any help I can get.

Regards

Gary Reabow.

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G80CS Crankshaft end float.

Postby A Moderator » Sun Dec 19, 2010 10:58 pm

Moved to here from Frequent Questions.

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G80CS Crankshaft end float.

Postby holland » Mon Dec 20, 2010 6:41 pm

Gary have you fitted the engine sprockets and measured it?
james

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G80CS Crankshaft end float.

Postby reabow gary » Mon Dec 20, 2010 7:59 pm

No. I pulled the crank shaft hard up to the drive side bearings, set up a guage on the end of the timing side shaft, then pulled the shaft hard up to the timing side roller bearing. I then remeasured the gap between end of shaft and guage; 0.030ins.
What should I have measured engine sprocket wise?

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G80CS Crankshaft end float.

Postby Don Madden » Mon Dec 20, 2010 9:10 pm

Tightening the engine sprocket nut pulls the crankshaft firmly against the drive side inner bearing. That bearing is a light interferance fit in the case & the end float can be adjusted by shifting it slightly. The short stroke timing side roller bearing inner race is a tight interferance fit on the shaft & has a lip on the inner side to position the rollers. The outer race, with the rollers has lips on both sides to hold them & floats on the inner. The outer is shrunk into the case. The rollers are 1/4in long & 0.030 float would not affect them much but I suggest setting the end float to factory recommendation. Note that the books show only the touring engine but when the specifications were written, they applied to the WD & early post-WWII engines which had a similar but smaller T/S roller bearing. The rollers were deleled mid 1947 & replaced with a one-piece "Top hat" bush. Cheers, Don.

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G80CS Crankshaft end float.

Postby reabow gary » Tue Dec 21, 2010 8:28 am

Don, Many thanks for the information. I think you are right; I will keep to the factory 0.012ins spec.

My timing side bearing is non standard. I sleeved up an aircraft roller bearing to fit shaft and crankcase, and left a flange on the flywheel side to hold the bearing outer shell and rollers in place and to prevent it moving out towards the flywheel. This caused the crankpin nut to foul the outer shell of the bearing. To cure this I milled one edge of the nut to get 0.2 mm clearance.

G80CS 1959 model, but was fitted with a roller bearing as well as the bronze bush. I have assumed this to be correct, and thought the tophat bush only applied to the touring engines?

Many thanks once more for your help

Regards
Gary.

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G80CS Crankshaft end float.

Postby Don Madden » Tue Dec 21, 2010 6:56 pm

I have sent off used bearings to a fellow in Australia who intend to copy them for sale. It may be awhile before his spares become available.

The North American section provides a ball bearing direct replacement that has been narrowed to fit but it does not have the same load rating as original. Ed Crowell in Calilfornia uses a larger ball bearing that has has a higher load ratiing than the roller. It has been ground narrower to fit but required the case to be machined out a little to fit & a thin sleeve to adapt to the shaft. Neither of these has the same function of the original but the shaft can float in the bearing. I have seen tophat bushes to replace the roller/sleeve bush but they were in brass, not bronze as they should be & I do not recommend them.

The AMC top hat was for WD/early engines to replace to non-available roller. The design was revised later, (1954?) & the special bush discontinued.

Cheers, Don.


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Re: G80CS Crankshaft end float.

Postby Matchymarty » Wed Dec 20, 2017 1:53 am

Great info. I'm assuming in order to obtain 'correct' end float, one spaces the inner and outer bearing apart?

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