Cappellini Moto makes a steel sprocket to replace the the rubber wheel (the small wheel) in the stock tensioner mechanism. This functions more or less just like the original, still retaining the rubber guide roller (the big wheel). http://www.cappellinimoto.it
(on the CB 250/350 page, scroll down to #72 "Gear tensioner overhault 'steel'")
Both options are kind of expensive... but not too much more than Honda parts.
I don't race. I emailed Todd Henning about what he would recommend for a street bike. He seemed to feel that the slipper tensioner is great for street applications, as well as racing, but that in his experience a new stock rubber tensioner is perfectly acceptable for street use... so I went with the stock Honda tensioner.
It seems the issue is durability, not function. Other, much more experienced members could comment on how long a newly installed stock tensioner lasts (when properly maintained, of course), a figure I would be interested in hearing as well...
Bill and Steve, I know both of you guys are/were mechanics and are knowledgeable in general... how long do these things typically last when new?
thanks for the links. i'll look into them. my concern is longevity on a non-race bike. i began the restoration at 17K miles, and i have no idea how the chain tension was treated prior to the ~150 miles i put on it. my guide and large wheel are pretty chewed up, but luckily the block didn't get the typical machining from the chain slapping it. i have located the guide, tensioner, and large wheel new old stock if they will last a good patch.
I would not be inclined to put a steel idler on the tensioner, too much inertia that the cam chain has to spin up which puts more load on the chain, decreasing life and added potential for something to go wrong. Aluminum would be a better choice, but then you've got dissimilar metals with a small surface area generating more particles in the oil. I would stick with the stock wheel cause they are still available.
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