By: Anonymous: Andrew ()  Monday, 06 June 2011 @ 02:18 PM ICT (Read 1599 times)  

O own a well-maintained 2003 Kawasaki ZZR1200 with 20,000 kilometres on the clock. I bought it new an have never abused it. So, why do I manage to get this motorcycle into what I guess you would call a 'false neutral' or 'in between gears'? I wear proper hard-soled motorcycle boots, but I still often get the transmission stuck between gears, and it makes a 'weird' noise that sounds like it's not properly engaged (which of course it isn't). If I pull in the clutch and fish around with the shifter, I might get it engaged. But if I don't and hear the 'weird' noise again, I'll shut the motorcycle down (for gear of doing any damage), pump the clutch a few times and I'm on my way.

At first, I thought this might be a characteristic of the motorcycle, but I bought a Triumph Scrambler as a second motorcycle, and this problem happens on it, too. I'm not familiar with how motorcycle transmissions work, so please tell me why this happens, how it can be avoided and if the weird noise is doing damage. It must be me, right?

By: ThaiDesign (offline)  Monday, 06 June 2011 @ 08:26 PM ICT  

I hate to tell you this, but I think you're right: It probably is you. As I was reading your posting, I began thinking about the various shift-mechanism glitches your Kawasaki might behaving; but when you said you're also experiencing the very same symptoms with your Triumph, and that you sometimes 'fish around with the shifter' and 'pump the clutch a few times' with the engine turned off, that told me what I needed to know: You're shifting too slowly and too gently.

Motorcycle transmissions are entirely different than car transmissions, in design and in the preferred method of shifting them. With either type, every shift requires two gears moving at different speeds to have their speeds equalized as they engage each other. Car transmissions have synchronizer rings that use friction to 'synchronize' the speeds of gears as they engage; those transmissions respond well to shifts made comparatively slowly, giving the synchronizers time to do their work. Motorcycle transmissions, however, shift through the meshing of gear dogs, which are peg-like protrusions on the sides of gears and that change ratios by engaging with similar protrusions or matching holes on adjacent gears. This type of gearbox reacts most favorably to quick, firm shifts so the mating dogs can engage each other almost instantly. But if you shift slowly and delicately, the dogs tend to bang and skip off one another as they meet, creating the weird noise you describe. They also often reject neutral between gears and potentially bending the shift forks that slide the gears from side to side.

I have observed this same shifting disorder with quite a few other riders, and when I've told them to shift much more quickly, they at first thought such a technique would damage their transmissions. But after they tried it and became adept at it - which usually required very little riding time – they realized it was their previous shifting style that had been harmful to their transmissions and that gear changes on their motorcycles had become smoother than ever before.

   

ThaiDesign


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