Monday, April 21, 2014

Rebuilding the Transmission

The transmission was pretty used up on the Hornet. Gears were abraded and worn to the point I did not want to use them. A person was parting out a ’66 on ebay and a complete transmission was purchased which was in great shape. While everything was apart the needle and roller bearings were replaced. The bronze bushings looked good. The BSA factory workshop manual was a nice guide for putting everything back together and for explaining what size shims to use and where. Once assembled, I checked the end play to assess the shims. The layshaft had .02 end float which was excessive. I installed the mid size shim BSA made and put the float at .005 which should be good. Optimal is .002 from what can be found on the internet.  It runs through all of the gears and should be a good transmission for this bike.

The original transmission above & below. 

17 (stock), 20 & 21 tooth final drive sprockets. I will be using the 21 to keep the revs down at highway speeds, which has been a problem on my '70 Lightning with a 20 t sprocket. 

One thing that works work well when replacing bearings is to heat the aluminum up to 350F in the oven. My wife is not real fond of this but has not thrown me out of the house for doing it….yet. The bearings come out very easy when the cases are heated up. I install them in the same manner. This came in handy for the needle and roller bearings and was used for the steel pinion crankshaft gear too.

New bearings installed. 

An additional point of focus was to clean up the shifter plate. The one purchased on ebay looked good but was bent. It must have been a common problem since the '67 plate was much heavier. I polished up the '67 plate as it was a little scraped up. This included polishing the detent surface as well as the track the shifter dogs slide in. I did not remove much material and only cleaned up the rough spots.

Rebuilt & ready to go in the case. 

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