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Transmission surgery - or swapping enduro gears into roadster trans


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I bought my 04 R1150R summer of 08, first BMW I'd ever even sat on.


One thing I noticed pretty much right away was the high first gear which seemed hard on the dry clutch in my hilly country. I've driven lots of vehicles with dry clutches incl high power hot rods and heavy trucks and so am sensitive to excessive clutch slippage.


Another thing was that on the predominantly 2 lane 60mph roads I travel, 5th gear was a little too low putting the engine in the very upper 3k rpm range when near 60 which makes the handgrips buzz, and with the wide spread between 5th and 6th that 6th is too high for those same 60 mph 2 lane roads resulting in lugging the engine. So frequent upshift / downshift. My old nerves in my hands and arms are in bad shape and just can't take the vibration, which was bad enough to cause major discomfort even with foam grip puppies and padded gloves.


I've wrenched on a lot of different vehicles incl engines, trans, diff's, etc, so am not afraid of digging into something like that. Doing some research, I first found the roadster trans & final drive ratios. Then I discovered the low first & sixth gears in the Enduro trans which got me to thinking. Would solve the high first gear but would take away too much speed in 6th for the occasional foray onto the interestate.


Then added different FD ratios into the mix, being that's the only other way besides trans gears to juggle the overall ratios.


Calculating road speeds vs rpm, it was readily apparent that the only cure for the low 6th enduro gear was to go up in FD ratio.


More research revealed that the only higher ratio in a straight bolt in FD was a 2.75 which doesn't have much of an effect on 6th, certainly not enough, and doesn't cure the 5th - 6th gear shuffle on 2 lane 60 mph roads.


Then I discovered that K1200LT's had a 2.62 FD as one of two choices. The FD housing is the same as the R housing, the K yoke mates to the R driveshaft slipjoint, the pivots/bearings and reaction arms are the same and attach the same. But the K brake disc and ABS ring attach to the hub, necessitating use of a K rear wheel which is the same size and configuration and appearance as an R rear wheel, just doesn't have the ABS ring and brake disc mounting bosses. Also the K caliper mounts differently and is not interchangeable, but the K and R rear master cylinders are the same cc volume, and the K ABS sensor plugs into the R ABS harness. Only non BMW parts was a custom 31" rear brake line I got from Spiegler.


So I shopped used parts for awhile and now have a 2.62 K1200LT final drive and Enduro gears in my trans.


Please don't think I'm touting this as something lots of folks might want to do - I had a specific goal in mind for rpms/mph for my 2 lane roads and I'm the unfortunate type of soul for whom it "either is right or it ain't" and it gnaws on me till I make it right. So mostly just sharing all the fun I had doing this


Am thrilled with the results. Even tho only a 7% overall reduction in 1st gear, it seems to make a very noticeable difference in reduced clutch slip and revving to get a smooth start.


And now my 5th gear is finally in a sweet spot rpm-wise for 2 lane roads. 3k rpm is 50 mph and 3.6k rpm is 60 mph. No lugging or vibration and no up or downshifting. And 6th is 3k rpm at 58 mph and 3.8k rpm at 75, which is as fast as this 64 yr old codger likes to cruise any more when I do venture out on the freeway.

And in 6th, 3800 produces no handgrip vibration like it does in lower gears.


Here's some pics of my trans surgery (yup, did it myself with my wife's help with the heating and hurry-up-before-it-cools stuff) and I'm (very) happy to report the trans shifts at least as smoothly as it did before. Of course a new clutch disc and slave went in too, but all else is OK as the bike only had 30k miles on it.


I shopped around and got good prices on the parts so still was less expensive than the risky (from what I've read) proposition of buying new gears and having them swapped into the existing FD.


Plus now I've got a good stock R1150R final drive, trans, rear wheel w/brake disc & ABS ring, and caliper to sell which should get me really close to minimal net cost for the whole thing.

I bought an enduro trans that had a bad front seal and input shaft that I took the enduro gears out of. Then I actually tracked down a good used input shaft! That took several months, but now with a new front seal I can assemble a perfectly good stock roadster trans.


As is often said, "I LOVE it when a plan comes together!"


Looking at the post it apparently doesn't show the links as links, so you might have to copy and paste into your address bar.




And here's pics of the K final drive in the R bike.





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I admire your dedication to solving niggling problems. I have to say that the only thing I don't like on my newly acquired R1100RT is where the gearing puts the engine at about 45 MPH and again at about 60 MPH, two speeds at which I find myself traveling a LOT.


I also wish the bike had a 6th gear for slab trips, I always seem to end up on some stretch of Interstate either at the end or beginning of a nice ride...

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With my 1100 I rarely ussed 5th unless 80ish on a freeway or droning.

Otherwise 3rd/4th carried all the high end speeds in those ranges

and rpm's kept above the referenced range also.

4500 plus for the rpm's worked great.

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Well, the way I've always been, if somebody else can do it

(and it doesn't involve higher math :-( or special tools that

I can't make and can't afford to buy) I should be able

to do it also.


Sometimes it even works out! :-)



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My sweet spot on my R11R is bewteen 4 & 4.5K, but the R is also geared a bit lower than the RT in the the lower gears. At 80 on the highway I'm right at 4500 in 5th.

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