"by ZFD » Sun Oct 30, 2011 3:35 am
Gentlemen,
The reason why Andover Norton switched from standard bearing spec. to C3 was that all bearing manufacturers now work at the lowest possible tolerance within the norm. In the old days they tended to be at the other side of the scale, manufacturing techniques being more "liberal" then.
The problem first became apparent to me with the C2 bearings Triumph specified for the T140 engines (part # 70-2879), in that if one used those lower-than-normal tolerance bearings the crank would not turn as soon as bearing and crankcase had cooled down (I deal in Triumph spares in my German firm, too). I therefore switched to standard tolerance bearings for the Triumphs (part# 68-0625). Shortly afterwards we had the same experience with the Norton Superblends.
Amazingly, I had complaints only from two workshops- Mick Hemmings and my own engine man Rudi Kolano. The others must have banged the too-tight bearings into the crankcases no matter what, or got their C3 bearings from somewhere else- in most cases I tend to think the former. One "Norton Specialist" I asked about it had "never had any problems", neither had any of the British "Triumph specialists". Why did that not amaze me?
We therefore changed our spec for 06-4118 from standard to C3.
Joe Seifert"
That was the best information I had at the time, things may have changed by now. This horse has been beaten to death here. Anyhow, the way I use the bike it won't matter.
Dave
69S