Clutchless shifting - bad for your bike?

[kwaka_crasher]

Modern motorcycles have a sequential gearbox meaning there are no synchro or baulk rings incorperated in there design:

That's not what sequential means. Sequential means the order of the gears never changes i.e. you can't go to 3rd from 1st without pasing through 2nd. What is of interest in the context of clutchless shifting is the fact they're constant mesh gearboxes with drive dogs.

While excessinve and prolonged preloading will indeed prematurely wear shift forks, this wear will not be excessively accelerated if you just lightly preload the lever to take up the freeplay on the drum mechanism prior to backing off the throttle to effect the change.

[The Pink Panther]

i gather if your wining and your race team has no probs with gearbox rebuilds.

[Maha]

There is about a million threads on this, covering every spectrum of response.

No theres not, thereis four, I have checked properly by using the seach function, hence the the dredge...
Anyway....I clutchless downshift from top to at least 3rd.....never clutchless upshift, didn't realize you could to be honest?
I don't preload the shifter either, its a matter of fact movement...coupled with rolling off the throttle until gear is engagaed....happens all very quickly.
So what is the general consenus on this subject?..


My Bike My Rules!

[bogan]

What are the other 3 then? I recall some good info (fuck knows what it was now though) in one I've posted in...

[Maha]

What are the other 3 then? I recall some good info (fuck knows what it was now though) in one I've posted in...

here....this is what search function brings up http://www.kiwibiker.co.nz/forums/se...archid=7243618

[bogan]

here....this is what seach function brings up http://www.kiwibiker.co.nz/forums/se...archid=7243618

Hmmm, search links don't appear to transfer over, all the ones I could find were old and didn't deal so much with downshifts anyway, just start a new thread!

[p.dath]

No theres not, thereis four, I have checked properly by using the seach function, hence the the dredge...
Anyway....I clutchless downshift from top to at least 3rd.....never clutchless upshift, didn't realize you could to be honest?
I don't preload the shifter either, its a matter of fact movement...coupled with rolling off the throttle until gear is engagaed....happens all very quickly.
So what is the general consenus on this subject?..

Beyond my mechanical capabilities, but the way it has been explained to me is that when shifting down you create a load on the dog gears, and the harder the shift down the greater the load. So I try to be nice shifting down and use the clutch and a blip (the closer the speed of the two on the down shift the less load). Less load should mean less wear on the dog gears.

The other way, shifting up, is not such of a drama, as the relative speed of the two is the same. So no clutch needed. Just, as you say, a momentary reduction in RPM to allow the dog gear to slip in.

[p.dath]

Funnily enough, I just found one of my old threads on a very related subject:
http://www.kiwibiker.co.nz/forums/sh...why-I-am-wrong

[Reckless]

I ran karts for many years with Kawasaki, Cadgiva and YZ engines with no clutch basket in whatsoever. The first thing we did to increase power was remove the clutch basket (except for the gear on the back). We used a dog gear disengage for road racing. Never blew a gearbox and Karts make thousands of shifts.

Pre Loading the lever will cause excessive wear and un-necessary.

On the road bike there's not much need but somtimes I do.
On the MX bike I do it 80% of the time both ways up and down.

The trick to clutchless shifting to be "off throttle", even if its only for an instant when you shift. Ie no load on the gears! This is essentual, Its about timing. Its not hard do it right and you wont stuff your box.

Just my 2c ????

[bogan]

The other way, shifting up, is not such of a drama, as the relative speed of the two is the same. So no clutch needed. Just, as you say, a momentary reduction in RPM to allow the dog gear to slip in.

The relative speeds are fixed either way though, as are the gear ratios...

In both cases its just matching the engine speed to wheel speed; the bigger the rpm difference, the higher the engine inertia, the greater the engine torque output, and the quicker the shift, all leads to higher forces on the gearbox components. How you shift determines what parts of components see the bulk of this force.

With downshift the engine characteristics is more of a factor than for upshifts. Upshifting you'll get less torque, which is fairly proportional to the gear ratio increase, but downshifting you get a lot more engine braking torque both due to the gear ratio change, and the much higher engine braking torque for higher revs. Another concern for me is the chain, I have to run a lot of slack and a roller, bashing it down is going to bounce that chain around and wear the roller out a lot quicker. Obviously correct throttle control could get engine braking really linear through the change, but its a lot trickier than for upshifts.

[ducatilover]

Bogan, does your bros lock up a shit load off the gas in the wet? Mine would in anything under 4th and 3rd in the dry would get snaky unless you feather the clutch.

[onearmedbandit]

Clutchless up and down here, 75% of the time. Gearbox has in my time done 40,000km and doesn't miss a beat (or a gear).

[tri boy]

Pointless on the road.
Helpful in racing.

A real challenge is shifting a crash box A7 through town when your loaded to the back teeth with double brown, and no lights, and license, and wof, and no clue............

[pete-blen]

I have clutchless shifted all my dirt bikes maybe 50% of the time for over 30 years..
Never had a dead gear box yet..
Have noticed Honda's like it more than the others... 2 strokes seem to un-load
the gear train quicker than 4 strokes when closeing the throttle...
When I was road raceing we use to hold the throttle full open.. clutch & shift..
Throttle never left the stop when up shifting... I did have quite a collection of
worn kawasaki & yamaha clutch plates..