bad gear box? help me shift!

last oil change I asked the mechanic to open the cover and have a look. We found the second gear is completely worn down. Perfect timing, just before my trip... my love/hate relationship continues with the Long March..

Right, the engine came apart, and in went a new second gear, new oil, fire it up... things turn. OK, thats a good sign. Put the engine in the bike, gas up .. tada !!! Wheels turning!

What's the problem? When I downshift from second to first, I hear a rattling sound until the bike starts pulling again. I'm scared this will grind my first gear down like the second gear. Now I try to use the brake to slow the bike down more than just using the engine, as I should be doing. Maybe I'm too slow on the throttle/clutch release? Well, if so that's because I want to slow down.

Any idea what could be the issue? What should I look out for? Chain tension is ok, chain is lubed, bike up-shifts just fine.

Just as an example when you replace the chain, you should also replace both sprockets, things should all be kept even, not one worn and one not worn.

I would think that would be the same for gears, putting a brand new cog into a set that has been worn is cost effective but not the ideal.

I think if one gear goes the other were following behind it, so unless its ridiculously expensive the whole set should have been replaced and then you have 500 km of wearing in, like a new bike.

Not sure but what you may be hearing is slop in the transfer, a new gear against an old gear.

I think using a 125cc gear case on a larger head eventually shows up as the transmission wearing out faster, aren’t all these 200cc-229cc engines sitting on gear case designed for a 125cc engine?

You should never engine brake on these bikes, the down shifting should be to avoid detonation not to brake or slow down, the transmissions cannot take that. That is why they gear them so tall, it give you more of a range to stay in the higher gear. Also why they offer so many with shift indicators, so as you can keep track easier.

Thanks, truer words could not be written. New gears at 12,000 km? I should have stayed with a 125cc bike that performs long enough to get me somewhere.. Anyway, now I just want to make it to Beijing and there the engine could explode to smithereens for all I care.