E: Engine Main bearing outer race width

oexing said:

While hoping you don´t burn me on a haystack, would you consider a metric conversion including lipped modern roller bearings that will not walk out in the case like with the factory design - crappy design anyway, but reason was non-availability then. There are some features favourable for these metric types: The o.d is 62 mm , so you don´t weaken the case in this critical place. Just skim the wornout 63,5 mm diameter to accept a sleeve, alu or brass, and get a calculated shrink fit with the new sleeve after pressing in and finish bore so the bearings will let loose at about 120 degrees for future repairs - for other reasons than walked out races.
I would hate to fit securing screws for the outer race, another weak spot right here. Punch locking the races is a horrible bodge as well, don´t even spend a thought on what that does to the roundness of the race at the punch spots !
The roller bearing NJ 2206 contains the rollers in the lipped outer race and the inner race has one lip for easy assembling. On the drive side outer bearing I take the type with no lip on the inner race so that slips through both bearings and will position the crank via an axial ring between bearing race and chain sprocket bush, no ball bearing here .
The timing side has the narrow roller bearing NJ 206, 16 mm wide, and another small NJ , bearing no. 4 . Here is one drawback, the oil pump worm does not slip past the rollers when the bearing already sits in the case. So I will try to thread the case over the crank while the worm lies loosely in the space between inner bearing and the small outer bearing and hope to meet its slot with the woodruff key . If no success after end of patience , no big deal: Heat the case so the big bearing drops out again - thread it onto the mainshaft, the worm onto its place, the small inner race from the timing side outer roller bearing as the last item on the mainshaft - and lastly plunge the enginecase heated over the crank , done.
I should add, my crank has 30 / 20 mm mainshafts, so for the 1 inch shaft you could simply machine an adapter sleeve for the 30 mm fit.

Vic

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peter holmes said:

Years ago I had my engine rebuilt by a very well respected Vincent engineer, sadly no longer with us, the crankcases were bored and sleeved back to standard, new bearings fitted and the flywheels aligned with new big ends fitted, the whole works really on the entire engine. The next time the engine was pulled down the main bearings had walked again, a bit perplexing to say the least, the next well respected Vincent engineer, now retired, refitted the bearing with loctite and also ground three little recesses in the outer bearing, drilled and tapped 3 small holes very close to the edge of the bearing housing and retained the outer bearing with the overlapping countersink screws. The engine has not been down since, but I do use a magnetic sump plug, if the bearing does walk and grind itself against the big end nuts I am hoping that I will notice metallic dust on the magnet, as yet nothing has shown up. It did seem to me a fairly crude method of bearing retention, any comments from anyone?

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peter holmes said:

Years ago I had my engine rebuilt by a very well respected Vincent engineer, sadly no longer with us, the crankcases were bored and sleeved back to standard, new bearings fitted and the flywheels aligned with new big ends fitted, the whole works really on the entire engine. The next time the engine was pulled down the main bearings had walked again, a bit perplexing to say the least, the next well respected Vincent engineer, now retired, refitted the bearing with loctite and also ground three little recesses in the outer bearing, drilled and tapped 3 small holes very close to the edge of the bearing housing and retained the outer bearing with the overlapping countersink screws. The engine has not been down since, but I do use a magnetic sump plug, if the bearing does walk and grind itself against the big end nuts I am hoping that I will notice metallic dust on the magnet, as yet nothing has shown up. It did seem to me a fairly crude method of bearing retention, any comments from anyone?

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Bill Thomas said:

You can buy Lipped Standard size main bearings, The problem is the outer track is 3/4", So has to be ground down, After grinding I think it has to be Demagnetized ?. It was in MPH a long time ago, I thought it would be a good idea for me, I don't have the tools or know how to do a job as good as you.
I also like your idea with the long ? rollers in your bigend, Who makes them ?.
Cheers Bill.

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