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CrazyMotorcycleGuy
Most users ever online was 4,519, September 2, 2015 at 03:26 AM.
Go Back   DCSportbikes.net > Sportbike Operation > Test and Tune

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August 20, 2003, 10:55 PM

Warning, this is boring, do not read !

Anyway, in case you weren't aware, I know little about motorcyle mechanics, but have been trying to learn. One of the many things that I have never worked on includes transmissions, so I decided to try to educate myself a bit. Started where I always start ( www.howstuffworks.com ) and read about manual transmissions in general. Then went to my trusty VFR Sevice Manual and tried to assimilate the information about the generic automobile transmission with my VFR transmission. Really a struggle at first. I couldn't figure out where the collars were. Then I noticed that some of the gears are fixed to the main shaft while others are fixed to the countershaft via splines. And, oh look, some gears have dog teeth and some have holes. and the 3/4 main gear is one piece. Aha! The gears themselves act in a manner similar to the collar in the generic manual automobile transmission. Pretty cool stuff. These guys that design these things are smart! I can see where the shift forks move the gears to engage their neighbor, etc.

Haven't yet figured out exactly how the shift drum and shift forks interact to engage the correct gears, so I'll have to keep digging.

Clutch is quite different, too. Instead of a clutch plate and flywheel, bikes have a clutch inner and several clutch plates and a clutch outer and several clutch discs. Obviously similar principles apply, but the motorcycle system appears to be an ingenious way to create a larger friction surface area within a smaller circumference.

Actually, ArlingtonRider got me started down this road with his question about the rear wheel spinning with the clutch disengaged, so blame him. I'd seen the rear wheel spin with the bike in neutral with the bike on the stand before and figured that with all those gears so close together, that the rotation of the main shaft moved the oil around enough to rotate the counter shaft. Wasn't sure if the same could happen with respect to the clutch and the bike in gear. I figured since it's a wet clutch, perhaps. With the splines on the clutch center and the groves in the clutch outer, I suppose it's possible. Hard to imagine that there would be much transmission of rotation from one to the other since the clutch plates and discs are in between. But I don't really know anything about fluid dynamics. Anyway, that's enough mindless rambling for the evening!

Yes, yes, I know! Nerd!


[Edited on 8/21/2003 by rddy]
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August 21, 2003, 12:23 AM

Oh, and Woody uses a fork to disengage the dog teeth from the holes in his main shaft! :o
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August 21, 2003, 09:06 AM

Dave - I assume you did not rip up your VFR after being inspired by my post!
Thanks for the information - as for my problem; most likely it is an adjustment. This is what I have learned so far.
My clutch not disengaging is probably a warped plate or adjustment needed.

When a clutch starts to go; is remains disengaged (loss of power, slip, etc). I am pretty clueless too. Every bike's wheel will spin on a stand, just probably not as much as mine. If the bike is on the ground and you put it in gear and feel a pull - you have issues.

Either way - my bike is going into the shop Tuesday to Rick at Fast Lanes to have my transmission rebuilt, and a general bike tune up. I have crashed it enough to warrant some professional service, and not my half ass attempts and 5 wrong attempts before I get it right work.

I just hope it makes through the next 3 days at the track.

And BTW - GERBILS and DOMESTICATED RODENTS are COOL.
Woody's testicles, and peanutbutter are NOT cool.
Try and keep the two as separate issues people, don't taint the rodents with Lee's balls.
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August 22, 2003, 08:30 AM

Quote:
the motorcycle system appears to be an ingenious way to create a larger friction surface area within a smaller circumference.
Exactly Dave! The metal dics are just like the flywheel in a car. The fiber discs are the same as the plate. When you pull in the clutch the plates don't seperate very far. JP's advice was right on...so was R1Meyers. The oil has viscosity. That is why the rear wheel turns in neutral while on a stand. Step on the rear brake and it will stop. That is also why the first time in the morning when you select first gear there is usually a clunk...gets worse the colder it gets (oil is thicker).
If you look at new fiber plates there isn't much material there...
HTH...

[Edited on 8/22/2003 by SteveZX9]


Steve
2015 Yamaha R1
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August 24, 2003, 10:30 PM

Someone kindly made a shockwave animation of a CB1 transmission, where you can controll the shift and see which sets of gears engage:

http://www.timberwoof.com/motorcycle...nsmission.html

Good stuff!


-- Chris
BMW R1100s
(previous rides: '82 KTM250, '95 CBR600F3, '98 Buell S3T, 2000 Hayabusa, 2008 R1200R)

"Any sufficiently advanced technology is indistinguishable from magic." -- Arthur C. Clarke
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September 5, 2003, 04:15 PM

Hey Arlington:

Before you go and spend cubic dollars to fix your tranny why donít you replace the clutch plates and friction discs to see if that solves your problem? Does you tranny pop out of gear or is it hard to get into or out of a gear? If not and it just is a slipping clutch, identified by the tach needle zomming up to red line much faster than your road speed indicates, you are spending money drop a motor out of a bike and split cases when you could perform the work your self in a few hours with regular hand tools.

Please describe your problem further!!!!


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September 5, 2003, 04:25 PM

hEY wOODY:

Some gears are even called sliders. These sliders are the gears moved by the forks that are moved by the shift drum, that is moved by the star selector that is moved by the shifter peddle, to engage with the fixed gears on the primary and secondary shafts of the tranny.

Your shift drum moves the shift forks in unison moving the gears that they are slotted into all at the same time. The slots in the drum determine what gear is engaged to what. Sequentially from first to neutral ,where no gears are engaged, to second and so on, and then backwards to first again.

Any thing not make sense?


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