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Motorcycle Discussions => British Bikes => Topic started by: peteR on January 23, 2024, 11:59:25 AM

Title: BSA C15 mainshaft bush. Phosphor Bronze OK or not?
Post by: peteR on January 23, 2024, 11:59:25 AM

Hello,
the mainshaft bush on my BSA C15 is very worn and is also loose in the timing cover.  I understand that the original bush was sintered bronze - but would it be OK to turn up a new oversize bush in phosphor bronze?

Thanks for your help

Title: Re: BSA C15 mainshaft bush. Phosphor Bronze OK or not?
Post by: cardan on January 24, 2024, 12:09:31 AM

I would think so, as most vintage engines use phosphor bronze in this application and a C15 is hardly a race bike. I'm guessing, but maybe sintered bronze has a structure that seems a bit more open than pb (?), so maybe it holds oil a bit better?

Leon

Title: Re: BSA C15 mainshaft bush. Phosphor Bronze OK or not?
Post by: 33d6 on January 24, 2024, 12:28:18 AM

In principle, no problem. Many motorcycle engines have had phosphor bronze main bearings. Of far greater concern is accurate alignment with the drive side bearings.
You hint at worn bearing housings. They must be rectified and correctly aligned first. Making an oversize bush and bashing it in a worn housing is a recipe for disaster.
The better you do the job the better the result.

Best of luck.

Title: Re: BSA C15 mainshaft bush. Phosphor Bronze OK or not?
Post by: peteR on January 24, 2024, 07:38:13 AM

Many thanks for your advice guys.  I'll tread carefully!

Cheers