cush drive lifetime

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mgrant

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April has been a brutal month for travel for me but gratefully it's done now, so I can get back into finishing up the sorting of my 74 850.

My last post was about an issue with the speedo gearbox, which I am going to replace (it was rubbing against the hub cover) along with the spacers on that side of the axle. When I pulled the rear wheel I found that 2 of the cush drives were mostly destroyed and in small pieces and one was still okay. These were replaced in 2000 when the bike was restored, but only have a little more than 1000 miles on them. Most of the miles have been spent at low throttle openings, although I have done some brisk acceleration runs and also taken the bike up to 105 mph once. When the engine was rebuilt the head was milled to raise the compression to about 9.2:1 and a new Norris SS cam was installed so the engine is making more power than stock, but it's not putting out full-race power by any means.

I have new cush drives to install when I put the rear tire back on but before I do, I want to make sure that nothing else is wrong that may cause the cush drives to deteriorate quickly.

How long should cush drives last under normal street riding use? Do they deteriorate with time and limited use (they were installed about 8 years ago)?

Is there anything I should look for that would cause the cush drives to deteriorate so quickly?

Thanks
 
One of the gurus might have a better answer, but they should if they are a nice tight fit, and they usually are, ask I think Debbie last month or so...anyway, a tight fit is important so they don't slam to pieces. After-market, poor quality? Some kind of chemical you use for de-greasing? Improper installation? Super loose chain adjust? Dropping the clutch? An evil tooth fairy?

I give mine the goose as often as I can see no place for the cops to hide, and mine are tight as a drum and a good 25 years old (750, 3 blocks) but you have an 850...might be a different horse of the same color. Wait for the ones that know what they are talking about...:wink:
Greetings from Germany...
 
The ones I use which last well come from RGM, they are in a hardish muddy green colour wiht a plastic fee,l but I always have a spare set ready as I have suffered before from them only lasting a few 1000 miles. From memory the ones that did not stand up well were a black rubbery plastic but don't rely on my fading memory.
 
They will deteriorate fast if your brake shoes are rubbing at all and heating up the drum.

mgrant said:
April has been a brutal month for travel for me but gratefully it's done now, so I can get back into finishing up the sorting of my 74 850.

My last post was about an issue with the speedo gearbox, which I am going to replace (it was rubbing against the hub cover) along with the spacers on that side of the axle. When I pulled the rear wheel I found that 2 of the cush drives were mostly destroyed and in small pieces and one was still okay. These were replaced in 2000 when the bike was restored, but only have a little more than 1000 miles on them. Most of the miles have been spent at low throttle openings, although I have done some brisk acceleration runs and also taken the bike up to 105 mph once. When the engine was rebuilt the head was milled to raise the compression to about 9.2:1 and a new Norris SS cam was installed so the engine is making more power than stock, but it's not putting out full-race power by any means.

I have new cush drives to install when I put the rear tire back on but before I do, I want to make sure that nothing else is wrong that may cause the cush drives to deteriorate quickly.

How long should cush drives last under normal street riding use? Do they deteriorate with time and limited use (they were installed about 8 years ago)?

Is there anything I should look for that would cause the cush drives to deteriorate so quickly?

Thanks
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