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Just curious as I don't find myself on a track with a motorcycle ever, but...

OK, straight cut, sequentially shifted transmissions such as the open-wheel variety, I have always had to "spin-up" on downshifts; heel and toe shifting style, for those familiar. Since I have never truly run a motorcycle often enough in such a situation where I was under threshold braking and rapidly downshifting such as in a race car, would this become necessary on the BMW transmission during hard deceleration and downshifts? If not, why not? My guess is the answer might be no, I say this because the same boxes we simply preloaded and "burped" the throttle for a few milliseconds and banged it into the next higher gear with no clutch, something (riding clutchless) Duane has mentioned takes practice on these bikes. Clutchless up-shifts on those transmissions were easy, but not 100% fool-proof, the preload was key, or you could find a false neutral, usually accompanied by a whole lot of grinding going on. Downshifting was even more of an art (heel and toe at threshold braking, down four gears is not so bad when everything else is going your way - much more stressful when you are doing so sideways looking at a wall looming in front of you...) Rookies usually got passed at the end of any long run due to shifting issues; some never overcame it... Of course now, microprocessors handle the throttle "burping" for everyone; some do the "spin-ups" as well (F1 comes to mind...)

I have always questioned this after seeing the guts and parts blow-ups of these transmissions and reading enough. Other than the apparent weakness of the dogs and their lack of precision from the factory (not matched, simply cast.) Is it this same difference I don't readily see in the BMW design that allows for not having to spin the engine up to match (OK, one usually exceeds it initially, but...) with the drive-train on downshifts, the same reason we can't simply preload the shifter and up-shift clutchlessly all day? I am unsure I know exactly how the designs differ all that much, those boxes we used to race and these BMW boxes.

Could anyone elaborate for me? BTW, I am not implying we should want to chance ripping a BMW box up on our bikes nor that they were made to take such abuse, just trying to understand something I do not readily... Also, it's really darn easy to pull in our clutch levers and unnecessary for us to attempt to keep power to the wheel 100% of the time at open throttle on (nearly) every acceleration - unlike a race car on a track.

Thanks in advance anyone that humors me...

Don't know the finer details of our gearbox's design, but I do blip the throttle on downshifts. I do it the same way as you do in a car (that heel+toe thing). Clutch in, blip, downshift, clutch out. It all happens in an instant and usually while on the front brake. It just became second nature to me after a while.

I don't like there to be a big mismatch when I let the clutch out.
It is mechanically impolite.

dougie wrote:Don't know the finer details of our gearbox's design, but I do blip the throttle on downshifts. I do it the same way as you do in a car (that heel+toe thing). Clutch in, blip, downshift, clutch out. It all happens in an instant and usually while on the front brake. It just became second nature to me after a while.

I don't like there to be a big mismatch when I let the clutch out.
It is mechanically impolite.

Yes, I do as well - anything with a manual; people who ride in my truck always inquire. My '53 it was/is mandatory for the synchro's are out in all but third gear. This also meant if one were in a "hurry" IE if you stopped at a stop sign and wanted to leave it like everyone else, you had to get the three-on-the-tree into third before putting it into first; otherwise the synchronizer drum was still spinning and ate up on the dogs pretty good on the way in (or, got "stuck" and you had to go neutral, then clutch out, then in, then first...) Seemed silly to need to "double-clutch" first gear at a stop...

I still would like to know about our BMW boxes though... Thanks for commenting.

Are you asking why we don't double clutch the bikes?

Chuey

dwire wrote:

dougie wrote:Don't know the finer details of our gearbox's design, but I do blip the throttle on downshifts. I do it the same way as you do in a car (that heel+toe thing). Clutch in, blip, downshift, clutch out. It all happens in an instant and usually while on the front brake. It just became second nature to me after a while.

I don't like there to be a big mismatch when I let the clutch out.
It is mechanically impolite.

Yes, I do as well - anything with a manual; people who ride in my truck always inquire. My '53 it was/is mandatory for the synchro's are out in all but third gear. This also meant if one were in a "hurry" IE if you stopped at a stop sign and wanted to leave it like everyone else, you had to get the three-on-the-tree into third before putting it into first; otherwise the synchronizer drum was still spinning and ate up on the dogs pretty good on the way in (or, got "stuck" and you had to go neutral, then clutch out, then in, then first...) Seemed silly to need to "double-clutch" first gear at a stop...

I still would like to know about our BMW boxes though... Thanks for commenting.

When upshifting or downshifting you , with the throttle, you match the speed of the input shaft with the output shaft of the gearbox to allow the shift dogs to slide together without trauma.
Trying to understand your question is difficult because of all the extra wording getting in the way.

My thought is:

You can speed shift these trannys for a while..up maybe a long time..but down is brutal and crashing with force.

My thrust bearing failed in my 75/7 and I was forced to crash shift. Matching speed and gear fairly smooth going up.. but going down was brutal... I would not recommend it as a regular practice as the tranny will evenually complain with a not so pleasant failure. I pulled in to a lot and hit the kill switch and re-adjusted the thrust pin to just get home.

The clutch and lever is there for a reason... use it wisely and the bike will perform to satisfaction.

There is no point in clutchless shifting unless you like to work on trannys' all the time. Their lives will not be prolonged by this abuse.

I stand by my opinion.

Jim, Ketchikan, Alaska

I've been continuously riding Airheads for nearly 40 years. I have never had any problem shifting them. You just shift them like they want to be shifted. A smooth rider is always a better rider. Airheads reward the smooth rider. These are mildly tuned touring motorcycles for mature individuals. Unless you are building a bike for racing I see no reason to explore clutchless shifting. If it ain't broke.... don't break it. When I want to get all nasty I take out my Jap bike and ride it like an animal. It doesn't see to care and goes really fast. Can't understand why guys want try and go fast on these old Merecedes like bikes.

Could you explain non sequential shifting please?

Zombie Master wrote: Could you explain non sequential shifting please?

Non-sequential shifting cannot be done with a sequential gearbox. To shift from 1st to 4th you must shift through 2nd and 3rd (and vice versa). The basic manual gearbox in cars can go from any gear to any other gear. World Rally Championship cars, F1 cars, shift sequentially, as do passenger cars with paddle shifters.

Zombie Master wrote: Can't understand why guys want try and go fast on these old Merecedes like bikes.

Not "go fast" ZM.
"A rather brisk pace."

Zombie Master wrote:I've been continuously riding Airheads for nearly 40 years. I have never had any problem shifting them. You just shift them like they want to be shifted. A smooth rider is always a better rider. Airheads reward the smooth rider. These are mildly tuned touring motorcycles for mature individuals. Unless you are building a bike for racing I see no reason to explore clutchless shifting. If it ain't broke.... don't break it. When I want to get all nasty I take out my Jap bike and ride it like an animal. It doesn't see to care and goes really fast. Can't understand why guys want try and go fast on these old Merecedes like bikes.

Could you explain non sequential shifting please?

Yes, just trying to understand the design...

QUOTE:

Zombie Master wrote: Could you explain non sequential shifting please?

Sequential = lever with no "pattern" just higher and lower gears selected "IN SEQUENCE."

Non-sequential = any transmission that one may select the gear ratio directly - you can pick any gear you like, whether it be the next higher or lower gear or not. One can't do that on anything that is sequentially shifted (LIKE ALL MOTORCYCLES I've ever ridden.) Think "H" pattern here...

dougie wrote:

Zombie Master wrote: Could you explain non sequential shifting please?

Non-sequential shifting cannot be done with a sequential gearbox. To shift from 1st to 4th you must shift through 2nd and 3rd (and vice versa). The basic manual gearbox in cars can go from any gear to any other gear. World Rally Championship cars, F1 cars, shift sequentially, as do passenger cars with paddle shifters.

Zombie Master wrote: Can't understand why guys want try and go fast on these old Merecedes like bikes.

Not "go fast" ZM.
"A rather brisk pace."

Yeah, knowing Mr. Penske's propensity to find ways to innovate around the rules like one year at Detroit their cars' engines were totally rebuilt to fire on two cylinders simultaneously - (torque monsters; they lapped everyone...) I have been awaiting the day when they find a way to go from 2nd or 3rd to 6th, for that "itty-bitty" fuel savings when the yellow comes out. Or perhaps a good thing on tracks with a lot of corners that are heavily trail-braked; don't know, but it has to be "good for something" if no one else can do it...