Ok, how should a K75 shift?

[crgrbrts]

Hello Gurus,

A remark by a correspondent in a post about "how to shift a K75" has led me to wonder what, if anything, is wrong with my gearbox. I acquired my bike, a 1990 K75S, with about 86K miles on the clock. I've ridden it an additional 5K this summer and over the past three months have treated the machine to spline lubes - front and rear - and a new clutch (with new springs, etc.).

I've developed a method for smooth shifting but wonder if I've simply found a "workaround" for worn parts. The transmission seems prone to false neutrals unless I blip the throttle when downshifting. Also, when at a standstill, finding first gear sometimes requires rolling the bike backward or forward slightly. Before the clutch replacement, it tended to slip out of second gear from time to time, but that's no longer the case.

So, what quirks, if any, does a low mileage or rebuilt K75-series transmission exhibit?

 

[cjack]

Hello Gurus,

A remark by a correspondent in a post about "how to shift a K75" has led me to wonder what, if anything, is wrong with my gearbox. I acquired my bike, a 1990 K75S, with about 86K miles on the clock. I've ridden it an additional 5K this summer and over the past three months have treated the machine to spline lubes - front and rear - and a new clutch (with new springs, etc.).

I've developed a method for smooth shifting but wonder if I've simply found a "workaround" for worn parts. The transmission seems prone to false neutrals unless I blip the throttle when downshifting. Also, when at a standstill, finding first gear sometimes requires rolling the bike backward or forward slightly. Before the clutch replacement, it tended to slip out of second gear from time to time, but that's no longer the case.

So, what quirks, if any, does a low mileage or rebuilt K75-series transmission exhibit?

The workaround for BMW transmissions is to keep the shift lever all the way lifted until the clutch is all the way out. That way the dogs find their place and you don't miss any shifts. Naturally with a dry clutch you might have to slip the clutch at a standstill (or move the bike) for an alignment to occur.

 

[kayseventyfive]

I find the 1-2 upshift the most problematic. The only way I get a decent shift is to shift early. The earlier-mentioned preload and follow-through do help, though. I don't recall my R90S being quite so bad. But it was clunky.

 

[crgrbrts]

Yup, that's also my experience with the 1-2 upshift. You can really feel the notch through neutral. Maybe my bike's okay after all. I've never ridden a K75 with fewer than about 80K miles on it, so I wouldn't know what's "normal."

My wife's F650CS, on the other hand, has the "clunkiest' gearbox I've ever experienced -- and I grew up driving farm tractors. There's no doubt that you've shifted successfully, though. That little machine is a blast to ride!

 

[98lee]

Here's an interesting article about BMW gearboxes:

http://www.roadkill.com/~davet/moto/trans.articles.html

 

[stewby]

I have 21,000 miles on mine and I can't say it has any quirks (yet). Shift from 1st to 2nd is smooth and positive. Best BMW clutch/transmission I've had out of 3.

 

[OfficerImpersonator]

The nature of a dry clutch is that you will frequently have to roll the bike an inch or so one way or another to get 1st when stopped.

I'd blame your shifting difficulties on unfamiliarity with the bike except for the fact that you've put a ton of miles on her, so that's obviously not the case. I do suggest that perhaps the new clutch requires you to get a better sense of the "feel" of how it operates and behaves in various gears in various situations.

I don't need to remind you that BMW trannies are famous for their "clunky-ness", and it seems as if you're simply experiencing a few of the quirks that make BMWs BMWs. I think you're "workaround" is simply you getting used to your bike - and how to most easily and efficiently operate the clutch/gearbox.

At least I'm hoping that's your situation!

 

[crgrbrts]

I think you're right. I adopted the downshift throttle blipping routine when my clutch was bad. It became a habit which I probably don't need anymore. I'll shift normally tomorrow and see what happens.

 

[bikerfish1100]

additionally, try upshifts at 5,000 rpm or above, on a "strong" acceleration. it really smooths things out. it's a trick i was taught by an R90S rider over 20 years ago, and it has always worked to perfection- be it airhead, K, or oilhead underneath me.

 

[breyfogle]

The nature of a dry clutch is that you will frequently have to roll the bike an inch or so one way or another to get 1st when stopped.

Hmmm, I don't recall ever having to rock my K75 to get into 1st gear.

 

[crgrbrts]

Got it!

Many thanks to all who've responded to my questions about shifting my K75S and Beemer gearboxes in general.

I've taken the advice and am now retraining myself. Missed shifts and "crunches" had really been few and far between, but this bike still changed gears in a manner I wasn't used to. (This is my first BMW).

So, as of this morning, I've been upshifting using a partial clutch pull, shifting more deliberately - though not harshly - and holding the gear lever up momentarily to assure gear engagement.

I've slowed my downshifts a bit and am using a more positive throw rather than a "toe tap" -- also with a partial clutch pull. I no longer blip the throttle as I found necessary before my recent clutch replacement.

The result has been good with a much better gearchange feel and no hint of missed changes or false neutrals. My new regimen has also relaxed my riding style a bit which, at my age, is probably a good thing anyway. The real test will come in a couple of weeks when I go down to Suches, Georgia to visit my son and toss the Beemer around on my old mountain twisties playground. Doing that smoothly and expeditiously takes lots of quick gearchanges.

Thanks again.

 

[pglaves]

Hmmm, I don't recall ever having to rock my K75 to get into 1st gear.

Dumb luck, then! Or you slipped the clutch slightly.

If properly adjusted, when the clutch is pulled and fully disengaged, the transmission input shaft stops turning. If the dogs are perfectly lined up with the stationary holes in the gear set engaged to the output shaft it will slip into gear. If not - then either the input shaft must turn a little (slip clutch slightly) or the output shaft must turn (rock bike forward or backward).

 

[crgrbrts]

Paul said -- and he would know -- :"...if not - then either the input shaft must turn a little (slip clutch slightly) or the output shaft must turn (rock bike forward or backward)."

Thanks very much for the explanation, Paul. So, I'm not crazy after all (at least about that).

Craig
Washington, DC
"Red Sonja" K75S

 

[breyfogle]

Dumb luck, then!

And I thought it was basic riding skill....

Seems like there is only three possibilities when stopped at a light/stop-sign;

(1) Tranny in 1st gear and clutch disengaged => Obviously no need to do anything extra to engage 1st

(2) Tranny in neutral and clutch engaged => The input shaft is rotating and a normal coordinated clutch&shift motion should engage 1st just as easily as a rolling downshift.

(3) Tranny in 1st gear and clutch disengaged => Nobody would intentionally do this, right ?

I suppose a fourth possibility would be a panic stop that left you in 3rd maybe 4th gear and stopped with the clutch disengaged. But even then, just a minimal amount of feathering of the clutch lever is enough to get the transmission down thru the gears.

 

[st3ryder]

Adjust or replace cable. Properly adjusted cable length, and pushrod bolt will yeild wonders if experiencing shifting problems. If the cable is too stretched, it cannot be properly adjusted. I realise there is a set limit/measurement, but each bike may need a bit of "personailsed" length adjustment to finally get it right. At least that's what I found on my K75 even after replacing the cable. I dicked with the cable length and push rod bolt adjstment on mine until I got it right for *my* bike. Bike shifts very smoothly now, up and down, and I now always use the "BMW" method for shifting gears on any bike I ride.

 

[pglaves]

And I thought it was basic riding skill....

Seems like there is only three possibilities when stopped at a light/stop-sign;

(1) Tranny in 1st gear and clutch disengaged => Obviously no need to do anything extra to engage 1st

(2) Tranny in neutral and clutch engaged => The input shaft is rotating and a normal coordinated clutch&shift motion should engage 1st just as easily as a rolling downshift.

(3) Tranny in 1st gear and clutch disengaged => Nobody would intentionally do this, right ?

I suppose a fourth possibility would be a panic stop that left you in 3rd maybe 4th gear and stopped with the clutch disengaged. But even then, just a minimal amount of feathering of the clutch lever is enough to get the transmission down thru the gears.

Or - you just rolled your K75 backwards out of the garage, climbed on and attempted to shift from neutral to 1st. I do this a lot. This topic is about the mechanics of transmissions - not about who is the superior rider.

 

[cayuse60]

Adjust or replace cable. Properly adjusted cable length, and pushrod bolt will yeild wonders if experiencing shifting problems. ....

Bravo...adjustment of the clutch lever adjustment screw and freeplay made all the difference in my K75's "shift ability".

 

[Troutluck]

When i had my k75, I experimented with various tranny-honeys to try to settle it down (proper clutch lever adjustment should come first). I found the plain 'ol 80w-90 gear oil worked best. That's what's specced, too. Valvoline makes a semi-synth version that's fairly cheap if your brain needs to see synthetic on the label.

As with all older BMWs, shifting is more of an agreement between you and the bike. I hated false neutral, too. They could be downright dangerous in the wrong conditions.