Very tight main bearings?

jug said:

I am having the same problem with the bearings I've fitted (FAG NJ306E.M1) also made in India, brass cage. These were supplied by Britishspares in NZ. I have no lateral movement at all with the crank installed in the cases. Had .020 with my old bearings from the same supplier with the same serial #'s also made in India.
Am going to split the cases again and take a look see. They were very tight during assembly. Have we got a bad batch of bearings? At aroind $A100 a bearing thats a real pain.
jug

Click to expand...

I would suggest warming the cases a bit. Like maybe 80 or 100 degrees F -set it in the sun. If that restores your free play I would call it a non-issue. Jim

jug said:

I am having the same problem with the bearings I've fitted (FAG NJ306E.M1) also made in India, brass cage. These were supplied by Britishspares in NZ. I have no lateral movement at all with the crank installed in the cases. Had .020 with my old bearings from the same supplier with the same serial #'s also made in India.
Am going to split the cases again and take a look see. They were very tight during assembly. Have we got a bad batch of bearings? At aroind $A100 a bearing thats a real pain.
jug

Click to expand...

Hmmm the plot thickens. I'll reassemble the case halves today again and try to lever for some movement. Other forums state you have to do this but I would have thought hand pressure would have sufficed.

The crank was very clean with no impedents. It is actually a very low mileage engine (about 2000 according to the speedo) and I don't doubt it. It was all original inside ie never been opened. The con rods looked like new. Just that tbe bike had been stored partially outside for 30 odd years.

Mark

Mark & Jim
I used a propane torch (as I have always done with no problems) to heat the inner races before fitting to the crank. Both sides dropped on easily with a satisfying clink. Could there have been any residue ( oil or Propane residue etc) left behind from the heating process leaving the inner race OD's greater after cooling on the crank.
I have never had a problem before, just trying to think out side the box. I dont heat the crap out of them, only enough for clearance. Thinking of pulling the inner races and polishing the mating surfaces to maybe remove any residue?!? Just an idea.
JUG

jug said:

Mark & Jim
I used a propane torch (as I have always done with no problems) to heat the inner races before fitting to the crank. Both sides dropped on easily with a satisfying clink. Could there have been any residue ( oil or Propane residue etc) left behind from the heating process leaving the inner race OD's greater after cooling on the crank.
I have never had a problem before, just trying to think out side the box. I dont heat the crap out of them, only enough for clearance. Thinking of pulling the inner races and polishing the mating surfaces to maybe remove any residue?!? Just an idea.
JUG

Click to expand...

I have never used a torch to heat a race. I warm them a bit over the light bulb on my solvent tank. It's pretty easy to damage the case hardening on a bearing using a torch. I use a press to install them.
I doubt this is your issue however.

I would guess the bearings are made on the tight side of the clearance spec. How tight -I don't know.

It would be common for the bearings to have no clearance if they are installed and the engine is in a cool shop. I have assembled engines and checked the end play in the afternoon and then came back in the morning before the shop has gotten up to temp and found I could no longer slide the crank. An hour later the clearance was back.

I wouldn't remove the race from the crank again unless it was necessary to replace it. Maintaining an interference fit on the crank is difficult enough without repeatedly removing and installing a bearing.

My biggest concern would be if the bearing is actually a quality item made by the manufacturer that is stamped on the bearing. There are definitely a lot of counterfeit parts around made by people who don't care if they last -or not.
A bearing that was slightly tight would be low on my list of concerns. If the clearance comes back with minimal case warming I would call it good to go. Jim

SUCCESS...don't you love it when you have a win. Remounted the the crank and cases and used a small screwdriver to lever the crank and presto....010 thou. Phew. I checked it 10 times to be sure and the same result each time.

I am going to run the bearings...I reckon they are genuine. If had bought them off Ebay I probably would not. The bearings have all the engraving that would suggest they are FAG but made in India.

Good to go!

Thanks everyone for your contribution.

Mark

PS I found this on a Triumph website: Quote:
Originally Posted by JohnA View Post
Just got a pair of roller main bearings for my TR7 project, and found that they have polyamide cages. These are glass-fibre reinforced polyamide (which I think is a fancy word for nylon). I'm wondering whether anyone on here has experience of using bearings with these cages, or has any tech knowledge of how they perform in British bike engines, eg: longevity, and problems or advantages over brass cages? Thanks.
Hi John,

I work for a bearing manufacturer as an application engineer so I thought I would respond to your question.

PA-66 GF bearing cages are fine for both motorcycle and automotive applications. They're quieter, have less inertia than brass cages and have good temperature stability up to 230C (may vary based on glass fill percentage). Brass cages can withstand much higher temperatures and are more robust during handling and installation. Brass cages can withstand higher speeds and acceleration forces. From a longevity standpoint, the brass cage may have an advantage but most bearings fail due to raceway spalling rather than cage failures. The causes for spalling are usually contaminated steel, water contamination or lack of lubrication.

I've fitted a few. Would only use the brass cage type but the plastic cage if said so is probably O.K. Inner race should tap into place ,not be bitchy tight and not slippy loose either. I would never put an open flame propane or other to an inner race of any bearing. Oven only on low or even hot water rag wrap. :!: