R90S transmission intermediate shaft - FRU?

[Dave Backmarker]

Last year I changed the transmission oil on my 1975 R90S and a dog dropped out with the old oil. With the awesome transmission repair DVD and magnificent tools from Cycle Works, I've opened up the transmission and found the gear with the missing dog and its on the Intermediate shaft. The manuals I have (Clymer and Hayes) confirm what I see on the major parts web sites that this shaft is only available as an assembly, a rather pricey assembly. Is this entire shaft and gear set really only available as a Field-Replaceable-Unit (FRU)?

Does anyone have any experience replacing this shaft? Tips and comments would be welcome.

I have all new bearings and a gasket set ready to go. Also, the shift forks and other gears are in great shape (the bike has 17K miles) so I'd like to refresh the bearings and the intermediate shaft. I plan on replacing the spring in the shifting mechanism too.

And, while I'm this deep, I have a new clutch disk and diaphragm spring and I've got the stretch bolts for the universal and the flywheel.

Thanks again to the men on this forum, the engine is running beautifully.

DaveM
1975 R90S, 2000 R1100RT

[pkboxer]

Dave,

I had 2 broken dogs on a gear on the Intermediate shaft.

I got a used shaft from a member for a good price, after an IRWA ad, and installed it.

Mine was a '74 transmission and the new one was the beafier one from '75 on, so I had to have the 1 shift fork machined to fit also.

I think that the only thing available new is the even later shaft, you would need the input shaft to match.

I would think that your '75 bike has the more reinforced gears, but if not, and it's not the same as my broken gear, I could try to pull the shaft apart and send you the gear.

I'll check tonight

[pkboxer]

Dave, just checked. Same break as on mine.

I thought there were 2 gears like that on the shaft. But there's only the one.

I just replaced the whole shaft, and was sure to reshim it too.

THe other two actually measured within spec.

Good luck.

[hools100RS]

Dave, did a layshaft last year (yep, dogs in the oil!!) and was told that we had to by a new or second hand shaft complete, Not so!!! Motobins (bless 'em!!) sold me a 2ndgear (10 quid!!) and a friend pressed apart the layshaft and pressed on the 'new' gear. Was pretty straight forward!! Worked well!!!

[Dave Backmarker]

Hools100RS,
I was studying the motobins bits and wondering if I might be able to replace just one gear. Once I get the layshaft extracted I will figure out if the gear is available on motobins. Thanks very much for the tip!!

DaveM
1976 R90S, 2000 R1100RT

[Dave Backmarker]

HoolsR100RS
Hmmm. The gear that's broken appears unique in the gear box and I don't see Motobins or anyone else carrying this single gear.

The broken gear dimensions are:
outside diameter: 58 mm
height without dogs: 25 mm
height with dogs: 38mm
Number of dogs: 4 on top, 4 on bottom
type of gear: non helical, straight cut.

Here's a pic.

The inner part of this gear is splined.

DaveM
1975 R90S, 2000 R1100RT

[Roy Gavin]

Try Motorworks in England - I recently bought second hand single gears from them.

[Dave Backmarker]

I purchased a new 15 degree intermediate shaft (very expensive) and the helical gears fit with my 1975 R90S output shaft beautifully. Ah, but the top, third and fourth gears from the top down (reference #) are different sizes and have different numbers of teeth. On closer inspection, I purchased a intermediate shaft for a "Sports" gearbox, up to 4/82.

.......Old..................New................................Delta
Ref # # teeth.... Dia (mm).. # teeth.... Dia (mm).. # teeth.....Dia (mm)
...1......17........46,0..........19.........53,6.............-2......-7,6
...2......31........74,5..........31.........74,6.............0.......-0,1
...3......21........58,4..........23.........63,4............-2.......-5,0
...4......28........68,1..........29.........70,0............-1.......-1,9
...5......29........77,8..........29.........78,0.............0.......-0,2


The #3 gear on the old intermediate shaft is damaged. If I press off the new #3 from the new intermediate shaft, I then have a size and ratio problem. I plan on calling Bob's BMW and asking if the 2nd gear (that's the one that mates with this gear on the intermediate shaft) will fit on the older output shaft. At $210 for the gear, I'd like to be sure. I'm $1,300 parts into this adventure now so I would like the additional $210 to solve my problems.

Alternatively, I could purchase an output shaft for a "sports" gearbox.

Any thoughts other than telling me I would have been better off buying a transmission from ebay would be welcome!

DaveM
1975 R90S, 2000 R1100RT

[Major Softie]

The Sports intermediate shaft can't be returned?

[Dave Backmarker]

MS,
I want the "good" gear from the new intermediate shaft, so I don't want to return it. I've just spoken to Bob's BMW and they feel the Sports 2nd gear should mate with the sports intermediate gear I want to press off the new intermediate shaft and press on the old intermediate shaft.

DaveM