Well I have to reassemble the bottom end in Mike's newly painted CB750 cases tomorrow, but today I did some more work on my 17 inch wheel conversion for my Yamaha FJ1200. I'm using 2009/10 FZ6R wheels, the rear will go on with some minor engineering, but the front has a 17mm axle, and my old FJ has a 15mm front axle.
After discovering that there's no such thing as a bearing with a 15mm inner and a 40mm outer, I settled for a bearing with a 15mm inner and a 35mm outer. (on the left) I thought about a few different options, but eventually a trip to another bearing shop in the country provided the answers I needed. I bought a bronze bush with a 40mm outer and a 30mm inner.
I could have bought one with a 40mm outer and a 35mm inner (in fact, I did) but I realised that I needed a flange for the bearing to sit against, or otherwise the bearing would just pull into the hub and the wheel could move laterally, which would be rather disturbing at speed. Boring the bush to around 34.8mm was a little too exact for my liking, but after only muffing one, I was able to make two nice bushes that I needed to first freeze the bearings, then tap them in to fit.
The new bearings were also 1mm narrower than the OEM bearings, so I was able to have a 1mm thick flange without any problems reusing the dust seals. The only problem was that the tubular spacer that goes between the bearings was now 2mm too short. After several minutes of quiet reflection, I machined two stainless steel washers to fit neatly between the flange and the bearing on either side, and was then able to use the spacer.
I used a piece of 320 grit dry sandpaper to remove any machining lips etc, and tapped the bearings into place. It was a very tight fit, but in this case, too tight is much better than not tight. It's all together now, I've put a 15mm axle in it and spun the wheel and everything feels right. Tomorrow I'll drop out the OEM front wheel and see what needs to be done to adapt the speedo drive, and I'll also have to look at brake calipers. Overall, it's slow going, but I'm happy that I've solved one major problem on my journey to 17inch happiness.