Far TOO Rough Shifting with HOT engine. HELP!

[barcelona_r65]

So, summertime has rolled around, and I wanted to go out for a nice long ride yesterday.  While crossing the city to get to the country roads I hit far too many traffic lights ... little by little my 1980 R65 was heating up, and longing for the open road.

30 mins of stop-and-go in 37ºC (98.6ºF) was too much.  By the time I tried to get past the last traffic lights I found that I couldn't downshift (or upshift for that matter) too smoothly... in fact, I couldn't drop into neutral at the light.  I've never had this problem in cooler weather, and when I let her cool down, it was fine again.  This morning all was back to normal.

Too much crunching and rough shifting for me ... Being that there's a few more months of nice hot weather ahead, I'd like to get this resolved instead of having to keep it down to short "urban" rides.

Any help anyone?

[steve hawkins]

I have heard that a synthetic gear oil might improve things.  Mine does the same when it gets hot, and next time I do an oil change on the transmission I will try this out.

My R100 also does this as well - so thats another one to do.

[montmil]

Perhaps your bike is asking you for a spline lube? Most riders find their gearbox becomes much more easier to stir after this maintenance chore.

Monte

[weasel01]

+1 on the spline lube, my bike was doing that too and I did the spline lube /throwout bearing service and the bike is shifting "perfectly" now even in super hot stop and go traffic.

[Semper Gumby]

+1 on the spline lube.

During the summer (april- october Atlanta GA) I uses a good semi-synthetic blend (Valvoline dark blue bottle) 85W140 gear oil in the final drive, drive shaft and the tranny.  Seems like it runs smoother.

[drewboid]

Difficult shifting sounds like the clutch was not fully disengaging. I once had similar problems and there was too much free play and the clutch did not fully disengage.
Not sure what the root cause was - thermal expansion or such but taking free play out of the clutch cable cured the problem. I'm now checking that the clutch cable is not fraying or stretching ( a symptom of an impending cable break).
ps - always carry a spare clutch cable.

[barcelona_r65]

drewboid ... you may be onto something there.  I took up some of the slack and it seemed to shift much smoother.  

I just had the entire transmission rebuilt in March, so up until now, all was just like new.  My mechanic advised me to keep an eye on my clutch cable and to make sure I take up the slack, or let some out ... I'm not sure ... but always to keep it tensed, but with a few millimeters of "play in the clutch handle" ... to make sure when it's released it's completely "closed" ...

If I understand the clutch well, when we pull the handle toward us, it pushes a rod that separates 2 plates that when released, clamp down on something and make it all spin (or something like that).  I guess that when the cable is too loose (or a bit loose then heated up to make it expand and gain a bit of length) then those plates don't separate as much as they should and something keeps spinning inside and doesn't let us change the gears ... I think.

I got spooked by my mechanic telling me to "Make sure you keep it tensed to where it's just right or you'll burn up the new clutch in no time" ... So maybe I'm a bit wary of adjusting the cable ... being that I'm not quite sure exactly what I'm adjusting ... This is my first and only bike (I've had it for 10 years now) and my previous "ride" (for 15 years) was a '70 Chevy Chevelle Malibu convertible with an automatic transmission ... same idea, different machine...   ) ...

... any tips or comments on all that?

[weasel01]

There is a very clear clutch adjustment procedure.
On your engine block on the right hand side there is a bulkhead molded into the block under and kind of behind the cylinder the clutch cable passes thru this.
You will see a rubber accordian cover then the exposed cable the plastic outer tube of the clutch cable stop at this bulkhead and the bare inner cable passes thru this bulkead over to the clutch control arm.
Measure 201mm from the rear facing side of the molded aluminum to the front facing side of the clutch control armn right where the cable goes in.
I cut a piece of stiff wire to the exact length then fed that thru the rubber accordion piece on the wire then adjusted at the handle till it fit perfectly inside those 2 points then removed it and put it in my drawer of BMW tools.
The control arm I think is at a 4 degree angle from the tranny.

[drewboid]

There are two places to adjust the clutch cable - at the handlebar lever and at the clutch arm at the back of the tranny. Ampliflyer's 201mm is probably correct but I eyeball the adjustment at the tranny until the arm is just back from 90 degrees. When the clutch is pulled in the arm will then move to and through the 90 degree point.
Then use the adjustment at the clutch lever so there is about 1/8 to 1/4 inch (3 to 6mm) of relatively easy movement before you feel a greater resistance of actually pulling against the clutch spring.

One last thing to check if you still find it hard to shift when hot - stop the engine and put the bike on the center stand with the rear wheel off the ground (may have to block up the rear end to do this) then put the bike in gear, pull in the clutch, and try to turn the rear wheel. It should turn easily. Slowly let out the clutch while turning the wheel and you should begin to feel resistance as the clutch engages.

If the wheel did not turn easily with the clutch fully pulled in you need to adjust the cable until it does.

Many of the BMW clutch cables look alike but are different lengths - the previous owner (PO) may have installed the wrong cable. Just a thought.   YMMV but I hope this helps.