Early alternator drive pulleys

[Shelly]

Hi all

I have a June '93 (date of manufacture) R1100RS and would appreciate information on identifying which pulleys are fitted to my engine as I believe there was a design change from June '94 with a retrofit kit available (?part no. 12 31 1 342 086?).

Engine pulley appears to be made of steel (magnetic), alternator pulley appears to be made of aluminium alloy (non magnetic) and the information on the belt is unreadable except for a BMW logo.

Recorded 58,000 miles, belt backing appears OK but 'V's' starting to break up and I suspect it may be the original fitment as I've no relevant service history.

Bike is running at the moment with just the occasional squeak from the belt at tickover when engine and air cold so it's still usable, says I , and needed for everyday transport.

Is the 4PK611 belt compatible with the early pulleys i.e. length, 'V' profile? I can't test it for myself as the alternator doesn't move due to the adjuster bolt being seized in the front engine cover. I'm thinking I may be able to 'run the belt on' at the roadside to get me home in the event of failure.

I know, I know, fix the adjuster problem (work in progress) then try it myself but time is limited and I need to use the bike between attempts at freeing off the bolt. If I force remove the original belt now and the 4PK611 doesn't fit I'm fekked as the original will get damaged beyond use on removal.

Is a seized adjuster bolt a common problem? Can't find any forum info but that could be down to my search ability.

I've read Steptoe's useful guide.

 

[ghiribizzo]

If you undo the rhs (of the bike sitting on it) bolt, top nut, bolt on lhs above the adjuster - the alternator will have lots of movement allowing you to remove the belt.

 

[Shelly]

Thanks ghiribizzo
Had another look at the bolt you mention and I found access difficult and I didn't want to strip further at this stage but I had another 'go' at the adjuster bolt with some force applied from the threaded end while turning the allen head. I finally managed to free it off enough to drop the alternator. Job done.
Old belt was a 4K611 with a 'V' shape, flat at the base and the 4PK611 is more rounded. Pitch is the same,designated by the 'K' in the name if my info is correct. I also measured the pitch. I'll keep an eye on it for the next few weeks for any changes.
Thanks again.

 

[davegs]

Belt

If it was squealing it's a bit loose, take the belt with you as on 1150's ther'es two lengths of belt not a lot but the wrong one don't fit!!.

 

[Shelly]

If it was squealing it's a bit loose, take the belt with you as on 1150's ther'es two lengths of belt not a lot but the wrong one don't fit!!.

Yes, a bit loose, not surprising as the tensioner bolt was seized into the front cover and the previous owner(s) probably looked and just put the cover back on.

Old = 4K611 Pirelli with BMW logo ( I reckon that's the original '93 belt)
New = 4PK611 Contitech from local motor parts sales, fitted yesterday, see post #3.

Both 611mm in length.

 

[Shelly]

Hi all

I have a June '93 (date of manufacture) R1100RS and would appreciate information on identifying which pulleys are fitted to my engine as I believe there was a design change from June '94 with a retrofit kit available (?part no. 12 31 1 342 086?).

Found relevant info elsewhere but I believe it applies to early GS models too so here goes:

Early pulleys:
Engine pulley = Steel, with three spot welds clearly visible on front face.
Alternator = Aluminium alloy.