J head bullgear bearings

[KevH]

I have decided to change the noisy bearings large bullgear bearings on my 1974 J head. After some research and reading the "Renovating BP" guide although the guide says that they are A/C bearings - Ive read they used M208 deep groove bearings and were ground for preload to act like A/C bearings.

My local BP agent/parts dealer sent me some 6208ZZ bearings [and charged me £150 for the pleasure - Ive sent them back telling them I could get those online for £26 pair]

What I read about 6208s is that the bull gear will be loose and cluch will rattle

My machine is a UK Made Adcock and Shipley and the bearings currently fitted are R&M 34LJ40 which is a deep groove bearing - but the bullgear has no play in it-just lumpy and noisy - Ive taken them out and cleaned them but they are still quite rough

Does anyone know if these were ground for prelaod - not sure how to check - the outer race thickness is 0.004" thicker than the inner - does this indicate anything

I can get a pair of 34LJ40 but would I be able to just put them in without any modification

 

[Oilyneil]

I had the same issue when rebuilding the bull gear on my 69 J head (also Adcock and Shipley). I went for 7208 CDU P4 bearings from bearing boys, not the cheapest but it has shut the grumbling bearings up and stopped all the rattles.
The 7208 are a/c bearings and measured the same as the original R&M I removed.

 

[KevH]

Cheers, sounds like a plan - the 34Lj40s would cost me £160 pair anyway

Guess they are put in back to back and tighten the locknut up as tight as possible?

 

[Oilyneil]

Thats how I did mine, I checked my bearing height on the surface plate and they were within a tenth of the originals.
I lubed mine with Kluber grease before installing and it's been 3+ years trouble free quiet since then.

 

[KevH]

There are some Nachi 7208CYDU GL[light preload] P4 on ebay for £120pair that would save me £80 compared to 7208CDU P4 on bearingboys.

Do you think these would be ok?

sorry for all the questions, not that clued up on bearings, Im guesing there,s not a lot of thrust on the bullgear hub