The rivets sheared on my engine shaft. When I stripped the engine, I discovered that the engine shaft was a loose fit in the flywheel. I found a good engine shaft, part No 66-644 amongst other scrap that I can use, but need to repair the bore on my original flywheel. The flywheel is a 94mm stroke 66-635 casting.
I have two questions.
1) Should I rebuild the flywheel bore and machine it to suit the engine shaft or bore it out and fit a sleeve?
2) Should I just re-rivet the shaft to the flywheel or should I weld the shaft in place as well? (A well respected Velocette owner recommended welding.)
Is there any special metallurgical info that I should consider?

email (option): pvlietstra@gmail.com

You can bore it out to fit the Gold Star shaft which is a larger diameter on the shaft that fits in the flywheel, I just sorted some using this method. thet are readily available and should cost about £80. It works well the other way too, you can use the flywheel on a Gold Star whose flywheel has worn by simply boring it out

email (option): davmax@ntlworld.com

If a good repair is carried out welding isn't necessary....

The mainshaft should be a light press fit into the flywheel, the rivets serving primarily to keep it in position..

For this reason care must be taken to align the rivet holes prior to pressing in the shaft as once in it is not really possible to move it radially...I have used silver steel rod for this in the past...

Some of the racers running B Series engines and Goldies thread the holes and use high tensile allen screws instead of rivets to hold it all together...

It is quite difficult to make a good job of the riveting...

With the lowish price and fairly ready availability of M20 flywheels it might be just as easy to buy another pair....

You didn't say..was it the drive side or timing side with a problem?Ian

email (option): ian@wright52.plus.com

The problem is on the drive side. It appears to have been a problem with a previous owner who built up the bore with brazing material. This all came out when it loosened the second time.
I like the idea of HT Allen screws, I assume held in with Loctite.
Failing any other advice, I plan to bore the flywheel out about 1/8" on radius and fit a sleeve.

email (option): pvlietstra@gmail.com

Hi Peter, If you bore out and sleeve the flywheel I would bore it to a slightly larger diameter on the 'inside face' and then press in a 'top hat' bush, recessed into the inner face of the flywheel...Then bore that to finished size for the shaft...

Otherwise I would think there would be a tendency for the bush to come out of the flywheel when you attempt to press in the shaft...

HT bolts are loctited as you mentioned...Ian

email (option): ian@wright52.plus.com