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Discussion Starter #1
After years of being a cruiser guy, I recently bought a K1200R. Love it, naturally. Could someone please explain the concept and mechanics of clutchless shifting. Is it damaging to the bike?
Thanks,
J
 

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jdj,

in a motorcycle gearbox, all the gears are rotating with the shafts, but the LOAD transfers thru whatever gear is engaged.

pulling in the clutch on each upshift is to allow a 'cushion' so load can transfer to the next gear without a hard inpact to the engagement dogs on each gear.

the same thing is accomplished by quickly rolling off the throttle and shifting without pulling in the clutch.

my R100-S racebike with 1050 jugs and 'very nice' heads will suffer from clutch slippage in a race IF I use the clutch on upshifts. Clutchless upshifts allow me to finish a race without having overheated and spun the clutch. Of course its a racebike and I don't expect the gearbox to last more than a few weekends.

I have clutchless shifted streetbikes Forever and suffered no damage, but typically save this technique when racing another streetbike or as a matter of convience when I am too lazy to reach for the clutch.

I am sure that if a rider makes clutchless upshifts his normal way of shifting, he is reducing the longterm reliability of his gearbox, when viewed over a multi-hunded thousand mile lifespan one would like to think his BMW is capable of.

Used correctly it will spare the clutch disk and shave 100's of a second off a dragrace or a laptime.

Any harm really depends on if the rider is 'hamfisted/footed' and what level of performance vs. reliability he demands from his machine.
HTH,
 

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The concept is fairly straight forward but I will over simplify with a conceptual explanation:

Your gearbox has an output shaft connected to your rear drive wheel and a power input shaft connected to your engine via the clutch. The input shaft can be rotating anything from idle at 1K rpm to redline. The output shaft can be rotating anywhere from stop to the maximum speed of the rear wheel through the tranni equivalent to say 155mph. On each of the 2 shaft are gears of different ratios (diameters and teeth) so when you shift you 'connect' the shaft and a gear rotating at engine speed with the shaft and a gear rotating at rear wheel speed.

If you have two gears on two shafts rotating at different speeds you can understand that the chances of getting the gear teeth to mesh together and join up the two shafts whilst moving at different speeds are going to be pretty slim. The purpose of the clutch is to disconnect power drive from the engine so the power input shaft momentarily stops rotating (actually it's slowing down) so you can connect the gears on the input and output shaft. The occasional 'crunch' you hear is the output gear forcing the freewheeling or stopped input shaft to mesh at the same speed. The gears are made to take these 'knocks' provided they are not powered (clutch is in). When you let the clutch out after shifting, the power is connected from the input shaft and gear to the output shaft and gear with the right ratio.

Engines have higher rpms than the rear wheel, so to reduce the ratio you have a smaller gear on the input than the output shaft. When you shift a gear up or down, you change the relative sizes of the gears so for the same engine and road speed before the shift you will not mesh the two new gears, unless the speed of one is changed.

For each shift there will be a road speed and a corresponding engine speed at which the gears on the input and output shaft can mesh without the use of the clutch. Generally the higher the road speed, and smaller the ratio change e.g 5-6, the easier it is to practice the clutchless change because speed differences in the two shafts going 5-6 are going to be similar. That's where you should start.

How do you know when to do the clutchless shift? You have to watch the tacho. and road speed first. Most riders will put a small amount of pressure on the shift lever whilst just backing off the throttle. If you are clutchless shifting up, you are trying to roll off the rpm just enough so the bike will be going at about the same road speed after the shift (but with lower rpm) as before. Going up is easier than coming down, but harder to get right going from shift 2 than 5-6.

Clutchless down shifting is far more difficult and virtually impossible below shift 3 because the ratios (shaft speed differences) are getting greater and you need practice watching the tacho and road speed with light pressure on the shifter to get it right. You can usually with light pressure on the shifter 'feel' when you hit the sweet spot for the shift.

I clutchless upshift all the time mostly 5-6, but generally not below shift 3 or with loads and a pillion. As long as you've developed a sensitivity at the toe and for any reaction or jolt from the bike, and worked to eliminate it, then I don't think you do damage - but it's down to your skill. You certainly save on clutch and hydraulic wear.

Going 5-6 is quick and lazy so I do it a lot. Lower gears need time to get the right rpm/road speed balance so I'd say it's slower to do if you are really pacing the bike and virtually impossible under hard acceleration without risking damage. The other lazy saving technique is double shifting up or down with clutch, but not under hard acceleration or perhaps fully loaded with pillion. The K has bags of torque and clutchless shifts get better with practice. Most of what I posted is memory and whilst I can do it successfully, getting all the details right when not riding is a tall order. So only practice 5-6 6-5 first, until you get no sharp decel reactions from the bike.

I started by reducing my clutch pull before shifting on higher gears to the extent I'm now hardly separating the clutch at all - that's good for clutches, bearings and you're well on towards clutchless changing.



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no clutch/bucks

I read a report somewhere on an oil company web site. General advice to motor cylists. The writer advocated clutchless shifting on the up change.

I proceeded to ride that way

Until club service day.

A rider there had just spent $5000 on a gearbox. All because of clutchless shifting.

Now if had have been any one else, I would have thought, riders fault. But this guy has done 400,000 on his current late model bike, has featured on TV commercials in the jungle of South America.

Back to using the clutch. Incidently, sold my last bike at 130,000. Clutch on the new bike and the old bike feel the same.

Some old truck drivers do not use a clutch either shifting up or down. I have also done it, especially in a battle tank. But I am the guy paying for this K so I shall declutch with care.
 

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MikeK said:
jdj,

the same thing is accomplished by quickly rolling off the throttle and shifting without pulling in the clutch.


HTH,
I have pretty good luck with clutchless upshifting on my K12RS but not on my R11R. Any idea why?
 

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Yes.. it will damage your bike if done improperly.. any bike.. and don't listen to those advocating it...They are in need of meds. ;-)

Bottom line... the clutch is there for a reason.. VERY smart enginneers designed it to be used for shifting ... why on earth would anyone choose NOT to use it when it's virtually an effortless, no-brainer action??.. You'll NOT be any faster...or smoother.. or sexier.. racers don't do it.. Sure you'll be able to brag to your friends that you don't need no stinkin clutch.. the smart ones will think you are a moron.. the uninformed mght think you are cool..

I'm baffled every time this comes up...

Just my opinion, but it oughta be yours.. "Shift with the force, Luke"

and that's all I've got to say about that..
 

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I have clutchless shifted for years up and DOWN!. 6th to 1st
I also will use the clutch. depends how I feel.
But you will get better performance with-out the clutch. "faster shifts"
I spoke to my BMW mechanic about this and he said " tranny is built like a rock crusher, I won't hurt it"

I also have a big rig with a 600HP eng. and 15 speed trans. I NEVER use the clutch up or down shifting.
You can not speed shift!! Big truck transmissions don't have Synchromesh gears.

When the engine reachs the top RPM say 2,000 you fully lift of the throttle and wait for the engine to lower it's RPM so that when you shift the trans. it will smoothly go in to the next higher gear. The gears will match up. maybe 300 RPM lower.
It will depend on the Trans gear ratio's. A close ratio Trans. will have 300 Rpms between shifts. A wide ratio may have 500 RPM drop.

Now this is for Advanced Truck Drivers Only. You know that big trucks have engine brakes right? No, Ok
It changes the engine into an air compressor, so it will slow down the truck. On big engines it can make 600 HP for braking. That's the BDDDDDUUU noise you hear when some trucks slow down.

So, you can use this engine brake to slow the engine down faster so you can shift faster.
NOW YOU Know how to speed shift a big rig!!!

HAPPY MOTORING
 

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Transmissions with straight-cut gears will shift themselves when you pre-load the shifter and simply release the throttle for a split-second. The K1200RS will do it. You don't have to pull the shifter, just pre-load it. The transmission simply changes gears the moment you unload the tranny (by releasing the throttle). Race car transmissions are built this way and racers use clutchless shifts all the time.
 

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mbohn said:
We'll need to let Kevin Schwantz know this. He is still teaching it at his Road Atlanta school.
While crewing for an AMA Formula Extreme racer, I get to entertain these young guys with stories from the 'good old days' when men shifted gears un-assisted by electronics, and read spark plugs rather than computer screens.

Every AMA FX and SS bike I've seen uses a Dynojet PowerCommander and a Quickshifter. Slightest pressure against the shiftlever triggers Quickshifter sensor, which causes PC to shut down ignition for a preset time (in milliseconds) and allow the rider to snick into the next gear. His hands/arms are then free to focus on keeping the motorcycle going where he wants it to go.......consistently around the track.

The advantages of clutchless shifts are only what the streetrider makes of them, but in racing it is a necessity......
 

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Kevin Swantz does it?? Oh.. then it must be OK for street riders with about 1000th of his skill... Funny Rossi doesn't... at least when he's on the track...

So an average street rider might shave off .002556 of a second my not using the clutch with a 50/50 chance of doing expensive damage to his bike... Sounds worth it to me... Geezz..

mbohn said:
We'll need to let Kevin Schwantz know this. He is still teaching it at his Road Atlanta school.
 

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Discussion Starter #13
Wow, I guess I opened up a serious can of worms here. I guess the heart of my question is "Will I damage my brand new, shiny, sweet, precious, lovely, light of my life (behind wife and daughter) bike If I don't use the clutch when shifting?" Some say yes, some say no. For the time being, I will use the clutch. The wife and I enjoyed Pirates allusion to "VERY smart enginneers"
-J
 

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Then my work here is done... and your bike will live forever.. being shifted as God and the Germans intended..

so it is written.. so let it be done..

jdjones said:
For the time being, I will use the clutch.
 

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Pirate said:
Kevin Swantz does it?? Oh.. then it must be OK for street riders with about 1000th of his skill... Funny Rossi doesn't... at least when he's on the track...
Ah, erm... what? Rossi doesn't? Well, he does use the clutch while downshifting, but he does not while upshifting, come on.

I don't think there's any MotoGP or WSBK currently racing without a powershifter. That means the rider stomps on the lever and the power is cut for a n/th of a second to unload the gears. Exactly the same effect - albeit quicker and less torque-wasting - as on a clutchless upshift.

On WSS 600s, powershifters are not allowed, so all the teams "trick" the regulations by rewiring the kill switch on a trigger (just like the passing flashlight), so the racers can preload the shift lever and just pull the trigger to have a "manual" powershifter.

Oh, albeit I'm a journo, you don't have to take my word for it - just read any test of a racebike, or ask any racer if he does use the clutch while upshifting. Downshifting, though, is a whole other story. But there's a lot of racers who just downshift without clutch - just ask any stroker racer, or Troy Bayliss for that matter. Clutchless downshifting *do* stress the gears, on that I do agree with you. But upshifting? If done correctly, no way...

CYA, Ed
 

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FastEddie said:
...snip.... Clutchless downshifting *do* stress the gears, on that I do agree with you. But upshifting? If done correctly, no way...

CYA, Ed
I guess the operable word there is "correctly"..... :ricky
 

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Two points:

1. I'd leave racing out of the discussion, since those guys rebuild their engines and trannies after every race or two. Irrelevant how they shift, don't you all think???

2. It doesn't have to be an absolute YES or NO on clutchless shifting; the right answer is somewhere in the middle... depending who you ask. Voxmagna laid out very well how shifting works, so everybody understands. And Pirate is right about the risk of damaging your transmission for trying. The risk goes up the lower the gears on upshifts, and same on downshifts, but you start with a WAAAY higher risk of damage.

My bottom line? Only on 4-5 and 5-6 UPSHIFTS, and on steady throttle or very gentle acceleration. So I only 'approve' 2 out of 10 shifting combinations... and with conditions <he he>.

As a final comment, I only do the above (4-5, 5-6 mild upshifts) because of fear of my slave cylinder crapping out on me (a very well known problem on KRSs), and because the chance of doing any damage to my transmission are next to none. But at the end, rather remove the transmission to replace a bad slave than tearing it down. Later.
JC
 

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Fast Eddie may have a point about clutchless/electronic cut-out shifting for racers during downshifting..The article I read with Rossi didn't mention this and I should have assumed.

However.. the question goes back to... Why?? Why would ANY street rider choose to do it? No one here has given one logical reason besides cutting down shift time which is.. oh about 3/4-1 freakin' second when done properly... Am I missing something here?? If anyone here is a professional rider where hundreds of a second make a difference of a trophy or not.. I might understand the virtues of all this... for the rest of us mortals out here who could and probably will permanently damage our street machine.. can the proponents enlighten me?? I have an open mind... Please..


sportrider said:
In the upper gears(4th->), it just drops in when blipping the throttle. I would be surprised if there would ever be any damage. If it clunks hard into gear, that's where I'd worry.
 

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