No end float

MFB said:

comnoz said:

At normal operating temps there is no interference fit to the bearings, they are free to float. With a used case the sun could easily heat the case to where there is no interference fit.

That is why guys who install a timing side ball bearing thinking it will locate the crank are doing nothing unless they install screws to hold the bearing stationary in the bore. Jim

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Exactly. And that's the main worry you have IMO. Jim has talked about spun bearings in the past (probably many times).
I devoured a lot of good advice from this forum when I was in the process of rebuilding my engine, and I'd say that what Jim doesn't know about engines isn't worth knowing.

If the bearing starts to spin it will wear the case and get even looser.

John Hudson's engine building notes recommend using bearing retaining compound to prevent bearing spin. He claims that the factory used it on new engines and I suppose he would know.

My cases showed signs of minor spin - I'd bet they all do.

I chose to fit my bearings with Loctite 641 bearing retainer.

While you have the engine on the bench, it's something worth looking into.

Cheers
Martin

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Actually rather than spinning in the case due to drag I suspect the bearing rolls around the inside of a hole that is slightly larger than the bearing OD. This roll is in reaction to the imbalance force which rotates in the opposite direction to the crank. This causes the bearing to roll slowly in the same direction as the crank rotates. Since the rolling is actually very slow little damage is done.
I have tried installing the bearings with 641 and on the next diss-assembly found no signs of locktite and the bearings had moved from where they were when assembled.
I did use JB weld the last time I put my lower end together but I don't know if it held. I really doubt that it did. Jim

The TS ball bearing you take out of early dommie motors don't seem to show any sign of spinning.
That I can recall seeing, anyway.
Will have a look if I have one to photo.

Didn't we see mention here recently that the bearing hole fit on 850 cases was adjusted at some point, to better hold the bearings ?

I have lots of ball bearings here that show signs of rotation. The bearings still rotate in a MK3 850 so if they adjusted them it didn't fix it.

The bearings don't seem to rotate in a newer Maney case. They are considerably tighter and that is why you must use a C3 bearing in them or you will not be able to insert the inner race. Jim

comnoz said:

They are considerably tighter and that is why you must use a C3 bearing in them or you will not be able to insert the inner race. Jim

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We have seen several folks here say the same thing about a stock 850 ?

Course, you risk the cases splitting if they are installed too tight.
Thicker Maney cases may help in this respect.

I haven't run into an 850 case yet that was tight enough to prevent the inner race from fitting -C3 or not. I have used .0015 shim stock in the bore before I installed the outer race to get a good tight fit. Then I had to use a C3 bearing. When I disassembled the engine the next time I found the shim stock had moved out of place and was rubbing on the side of the crankshaft. Jim

hobot said:

Martin please please please remember to let us know when able, if the off the shelf made for it bearing glue actually holds in our application. I am rooting for you to be the 1st with such success. JIm uses JBWeld which I'm quessing if just right escess might pile up slipping bearing in to act as its on shim behind race.

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Hobot I hope I'll never have to dismantle this engine again. If I maintain current frequency I'll be 90 when doing the next one.

However I can report on how it holds when engine has been assembled but not run, because I first fitted Standard fit bearings supplied by Norvil which were too tight when engine fully assembled.

Even with the cases really HOT I had to drive the bearings out with some gusto.

By comparison the previous unloctited bearings could be shocked out by banging case on wood block with somewhat less heat.

Of course this doesn't compare with an engine that's been used in the real world.

Cheers
Martin

PS don't tell anyone this, but I used an oil stone on the drive end of my crankshaft to reduce excessive tightness of the inner race caused by some small axial gouges in the shaft.

Martin

Martin I too once thought I'd be too old to care on my next, then next, then next like 5 or 6 times now, so wishing you better mechanical parts luck and road fates.
I only thot bearing tightness refered to internal ball and races but neat idea if they have em with outer races thicker to take up bore wear.

What I'd most like ya to do if not also more a pilot than mechanic like me, is run it w/o shims or glue and see where the crank just naturally ends up for some insights and maybe reason not to shim symmetrically on either side. Alas I'm a hick in the woods now and my early mentors Mr. Hudson and Wesley didn't bother to shim so neither have I.

Ugh I'd never use a stone on such fine finish, I use a file like on cam lobes to recover. Anyway glad you got past your "blank staring British Iron state". I never expect to either of course.

The speedodometer show just over 8k and PO swears that its the actual mileage. Apparently when he it put it away in 1975, the last time it was registered for the road, he filled the barrels with oil. That, along with wet sumping completely filled the crank case. I learned about this after I pulled the spark plugs to kick it over. I still have oil dripping from my garage ceiling from the gyser of oil that shot out. My point is that when I dissasembled the motor I found it to be very clean with no rust or pitting anywhere that I could see. So after reading the posts on this thread I think I'll just have the barrels honed, put new rings on and reassemble the motor without digging any deeper into it. Thanks everyone for your help. I really appreciate it.

Art

only takes a few hundred miles if in gritty place and fliter boot leaks. ugh. Otherwise might just put in new rings, check the end gap and if close to .0124" should be good to go. Install dry or with Bon Ami or the about identical power TS rings sell now and say only use wd40 if you must as it evoporates off mostly before start and flashes off on first ignition. Some rebores are done tad undersize as was my Trixie case with scoring a slight touch up hone to remove them still left bores .oo5" undersize from standard size of rebore .040" over. You cam should already be bedded so start up and run up 3-5000 right off to get oil going and seal rings in about as fast as oil shows back in tank, under a min.

If ya slowly roll and roll bearing Dry many rounds you may feel at some point a click or instand of drag then free a long while then again a drag hang up, if so toss em, if not just stick em back in.