DS and TS crank bearings

Have opened up my engine tonight, am pretty happy with what I have found, open for opinions..

The engine normally have a NF306 DS and standard 306 TS.

My engine has two NJ306's, one each side, so no fixed point bearing on TS, both lipped roller, they are both bronze case FAG, very good quality and condition, is this a normal way to set up the engine with two lipped rollers ?, does one need to shim for a maximum end play ?. Opinions ?.

Unless really truly racing around it don't matter a whitworth. Rods center crank but also the oil pump screw drive sucks it to TS anyway. 750s came with flat roller on DS and ball bearing on TS. Past drag racers preferred the thinner 750 cases and TS all bearing to take up more crank flex at hi rpm. Balls tend to wear out faster than ollers is about only down side to them. Dragsters back then would rev to 8-9000, I now cause I had one marked at 9000 and never blew it up, just wore out clutch. My pre-Ms Peel Combat was famous test bike in our area, I ran snot out of it too. When opened to fix leaks and renew stuff at 30K+ miles I found all style flat DS roller and ball on TS, both in fine shape, send to expert to verify they were for the record.

Best to shim in case as keeps inner race closer to crank cheek stress riser and easier less damaging to remove outter races than inner off crankshaft to shim. Ken Canaga is shooting for .004" slack in my Ms Peel, as cases expand more than steel crank so clearance opens up running.

Definitely need to shim for end play with the later rollers on both sides. If your engine was assembled properly, the end play is probably already set correctly. It's easy enough to measure. If all goes well, you won't have to remove the bearings or races, both of which are kind of a pain. Several different opinions on correct end play. Norton Owner's Club says .010" - .020" in one place, .010" - .030" in another. As I recall, Norton recommended .010" as the nominal end play. Most of the racers I know prefer something under .010". I've set them up as tight as zero end play, and had them work fine in race bikes. As soon as the engine is warm, the difference in thermal expansion between aluminum cases and steel cranks provides some end play. I don't recommend that. It's too easy to get them too tight by mistake. I normally shoot for as little as possible, but settle for anything under .010". I prefer to fit shims behind the bearings in the cases. Some people prefer shims behind the inner races on the crankshaft. I've seen street bikes with them as loose as .040" witn no noticable problems.

Ken

Thanks gent,

Am swapping over engine cases, hence all the questions, I will correct the end play in due course.