Britbike forum Forums British Motorcycle specific Brands Norton bulletin board Superblend replacement ball bearing ?

Just to re-confirm what I had found in the past I pulled an old virgin 750 bottom end off the shelf and checked the end play. It had a tight .002 IN.- about right for a ball bearing.



I stuck it in the oven at 220 F. for one hour.



The end play was then .034 and I could move it back and forth by hand.



I came back and checked it every few minutes as it cooled and it got tight enough that I could no longer move it with a screwdriver when the temp reading was about 160 degrees with my infrared but I wouldn't call that real accurate.



That's why they move around. Jim

I've always suspected this and fitted shims between the inner races and crank shoulders,if necessary.Aim for no less than 0.003" end float and have the conrods central in the bores.

End float could be 0.005" more than that,when the engine is hot.It not only affects conrod centrality,but also primary chain alignment.
With a 3-piece timing-side roller,it's easy to check end float before the crank pinion is tightened.

The outer race is not actually skidding in the housing when the engine is hot (or it shouldn't be).It's rolling around inside a housing only slightly bigger than itself.At 0.001" clearance,it would appear to rotate in the housing about 2 revolutions per minute,with the engine at 6000 rpm.This might be a good thing for bearing life.The major forces are not always happening on the same spot on the outer race.

It seems to work and not cause problems.

If the timing side bearing is pulled up tight against the crankcase wall, and the half time pinion gear and oil pump drive are pulled up tight on the other side of that wall, remind us again where the bearing is going to "move around" to.

Nortons used this system on twins for 20 years, and singles for more years before that than I can count, if there was a problem with timing side ball bearings spinning in their housing then someone would have noticed by now...

As someone suggested, maybe the roller type have more friction.
Maybe not all bearings have exactly the same external diameter ?
A fraction smaller could be a problem ?

Please remind me what is "pulling" the outer bearing race tightly toward the timing-side,when it is no longer held by the interference fit. Possibly the oil-pump screw is pulling on the crank?That would make sense.

This is merely referring to when the bearings and crank are fitted in the crankcases. And the timing side bearing setup.

Now, I've not investigated race Commando engines, but dommie bearings when you heat the cases and get them out look like they have never moved in their life. At least the ones I've seen.
Ball bearing on the timing side, of course.

Dommie engines being renowned for their relative lack of main bearing wear. And general bottom end strength and reliability.

Compared to AMC engines, that broke cranks until 'meehanite iron' (was it ?) came into it. And Triumphs, that had 'big bearing crankcases' to fix early problems...

Yes, but your findings are based on the bearing and case both being at the same temperature?
Under normal running conditions I would've expected the bearing to get hotter than the case? If so, then under such conditions the outer bearing race would expand more than it would do from simply being heated in an oven inside the case?

Can't readily find the instructions for installing the timing side ball bearing, but isn't that why you shim behind it so there would be nothing like that amount of endfloat posssible ?

I have seen it mentioned somewhere recently that having an old bearing, with the centre ground out of it a little to permit easier install on crank to measure required shims.

Anyone here recently installed a crank with timing side ball bearing ?

Perhaps what is needed for hardworking bearings is a retainer plate, like the (race) single cylinder Nortons use ?

http://racingnorton.co.uk/.media/394071932799.png

Is there enough meat in the outer race of a superblend bearing to have a semi-circular recess spark eroded into it for a retaining peg ? Does anyone know how the japanese handled this situation ?

The only times that I can recall seeing 'pegged' main ball/roller bearings in Japanese engines was when the crankcase had a horizontal joint.

Maybe true, but as the engine was cooling the cases would certainly cool faster than the crank and bearings and it still had no grip on the bearings. Plus the expansion rate of the steel bearing is so much less than the aluminum the bearing would have to be a lot hotter to maintain an interferance fit.

I have also checked this on a bike that had been run up to temp and got similar results.

Most Japanese engine have a plate and screws holding the bearing in place or there is a cast in steel insert around the bearing.

If you want to control end play you need to install shims whether or not it uses balls or rollers.
If you are using a ball bearing you could alternately use Dunstalls method of installing screws. Jim

I just don't think that results obtained by oven heating a case can be a truly accurate representation of what actually happens under normal operating conditions.




I would be interested to hear how you obtained those results?

Bon even if you use a ball you still have to shim the crank to get it close to being centered on the bores, if not having to shim is the only reason for not using a 2 roller mains then you are actually saving nothing. When I used to fit a ball bearing on a B40/C15 driveside I still shimmed before final assembly to get the conrod near center, on final assembly the crank was pulled up tight to the driveside bearing and running endfloat was that of the bearing but the con rod was in the center because of the shims. This is even more true when putting a Norton crank in Triumph cases, ie not even made in the same factory.

Ok, here is real operating conditions. The first handful of used bearings. All of them have varying degrees of polish and scratches around the OD. The bearing in front had been run only a few minutes and does not show the scratches.



The sides of the bearing all show a witness mark also. The mark on the rear bearing is deep enough to feel with your fingernail.





Those marks were not there when they were new. Jim

Thanks, Jim, I think the bearings certainly provide more tangible evidence than the 'oven' test.

No worries, I found it hard to believe too many years ago when I pulled one apart after a short highway run and found the bearings were not in the same position I had installed them. Jim

Its been an interesting thread so far , you have talked about the outer race turning in the cases , does one side turn more then the other ? Eg drive side being under a heavier load rotating more then the timing side ? Also the inner race being subjected to a similar friction load , do these rotate on the shaft at all or does the fact that they are mounted on steel with a similar coefficient of expansion eliminate this ?

In theory, a well built engine in good condition should have NO spinning or turning of the bearing outers or inners, under any circumstances. Anyone else seen evidence of this ?

I've had some (early) dominator engines apart, and the bearings were a real bear to remove - very solidly locked onto the shaft, and VERY firmly fixed in the cases.

P.S. The driveside and timingside bearings get a fair trickle of oil through them to lube them obviously, this should also cool them enough to keep them locked there ?

Oil rarely gets to anywhere near the crankcase temps Jim is quoting, is there something we are missing here ?

I have no way of knowing if one bearing turns more than the other in the case. I just know they both turn with little to no damage.

The center race should never turn on the shaft. I have seen that happen and serious wear on the shaft because of it. I avoid removing and replacing inner races any more than necessary as a small amount of interferance goes away every time the race is pulled. If you need to shim it just heat the case and the outer race drops out with no damage so you install the shim there. Jim

Gents .. This question is slipping away from the original issue, but 'I've always wondered'....
If main bearing races all but fall out of the crank cases when heated to 300F in the shop oven, do they loosen in their bores when the engine is run hard/hot?

Also why do the mfgs of many Japanese bikes bother to fit cast in steel liners in main bearing case bores? Nice, but the cost adds up for the mfg eh?

I have a Gold Star road bike engine that I had noticed witness marks on the drive side roller bearing outer race retainer plate, indicating the race had been turning in the case. As vagerly remember, I measured 2 thou interference fit. Being 'in a hurry' (aargh) I used 'green' Loktite bearing retainer. A bodge I know. Have any of you had good/bad results doing this?

A steel or bronze housing secured into the crankcases by screws would seem to be the ideal solution , if the casings were thick enough to take them and retain enough strength for a tuned engine.

Dave,
Locktite stud and bearing mount was my first action when I noticed the bearing races had turned. I had pulled the recently rebuilt motor back down after a popular cam builders cam had decided to break in half. I coated the bearings and dropped them into a hot case and though that would solve that problem. I put the original cam back in it.
I ran it a year or so and tore it down for a another cam change and saw that the bearings were not where they were when I put them in again. I heated the cases and the bearings dropped right out and there was no longer any signs of locktite except a bit down in the corners.
The next thing I tried was shim stock around the bearing which ended up costing me another teardown to remove what was left of it after it worked it's way out and rubbed on the side of the crank and left pieces of it in the sump screen. After that I just put it back together with nothing and rode it. Since then I started looking closely at every motor I get into and have noted that they all show sings of turning. I build 5 or 6 motors a year anymore.
It's now been about 35,000 miles since I had the bottom end of my bike apart and around 50,000 since it was competely rebuilt and it still runs fine although it has gotten a bit noisy when it's cold the last couple years. Sounds like pistons to me. I plan on installing a fresh replacement motor this winter. Jim

One final question about superblend bearings , the local bearing factors have only bearings with synthetic cages in stock , can these materials stand the heat of an air cooled engine or would i be better off waiting to get brass or steel caged ones ?

I have used both without any problems in the short run. I have a feeling the brass cage will outlast the plastic cage over time. I have seen old cracked plastic cages but I have yet to see one that came apart.
Given the choice I would spring for brass. Jim

The outer race is not actually skidding in the housing when the engine is hot (or it shouldn't be).It's rolling around inside a housing only slightly bigger than itself.At 0.001" clearance,it would appear to rotate in the housing about 2 revolutions per minute,with the engine at 6000 rpm.This might be a good thing for bearing life.The major forces are not always happening on the same spot on the outer race.

It seems to work and not cause problems. [/quote]

Pete,
I never really though about the bearing rolling around the inside of the bore but after I thought about it for a bit it does make sense.

I always figured there was probably some wobble to it also because the outside 1/4 of the OD always seemed to be polished more than the center. Possibly because the crankshaft is flexing like a jump-rope? I have a feeling the bearing may not last as well if it were retained so it couldn't wobble. I suspect it would cause extra loading on the edges of the rollers. Just a theory. Jim