Transmission Repair

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Transmission Repair


Post by Scrap » Wed May 20, 2015 10:56 pm

RE: 57 FL 4 speed.
Wish to cure a bad leak at the main shaft bushing. I have disassembled the gear box (how to wrench your 74 tranny in the Kbase). While my back was turned, leprechauns mixed up the rollers from the left and right side of the countershaft. I have miced the rollers and they all seem to be equal. How serious is this? Nothing in the article as to how to measure the clearance or what is acceptable regarding the counter shaft rollers. I see oversize rollers are available. This is not an everyday rider anymore. Would it be worth changing to caged bearings? Can this be done with the original shafts? What about the value of using the later main shaft with the oil seal on the end of the shaft? I can't say that was ever an issue with me when I used this bike daily. I've owned this bike since the 72 and I don't believe the transmission has ever been opened. The gears, dogs, forks all look excellent. I have no desire to use Andrews gears I just want to put it back together so that it is as reliable as it was and minimize the leakage. My first attempt to fix the leak was to install a new James Gasket MDG seal and Ray's O ring spacer. It was not enough, I filled it with mineral spirits and it all leaked out from the bushing while sitting on the jiffy stand after a few days.

Also any advice for fitting the new main shaft bushing will be especially helpful.


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Re: Transmission Repair


Post by old.wrench » Thu May 21, 2015 4:15 am

After finding 2 different diameters of rollers in the same bag (new ones!), I mic every roller I use now with a good micrometer.

You may be aware of this, but it might help someone - When fitting a new MDG bushing to fit your existing mainshaft, you want to make sure to measure the shaft at the end just past the taper where the shaft comes up to the full diameter (one inch), and also in the area where the MDG rides. If it's an older well-used shaft it may be less than one inch in that area where the gear rides. If it is, you can chuck the mainshaft in the lathe and even that end of the shaft up so you have a constant diameter all the way from the area where the MDG rides, to the end of the straight part where the taper starts.

I learned about that the slow and hard way :) .
On the very first tranny I rebuilt, I carefully pressed in and very carefully reamed my new MDG bushing to point where I could just slip the assembly over the end of mainshaft and I was looking forward to a nice fit, but when I slid the MDG a little further down the shaft to where it needs to ride, the fit was sloppy as hell. I'm pretty sure it would have leaked nearly as bad as it did before with the old bushing.

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