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SWM tl320 1982 jammed gearbox

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Hi All,

While doing a pivot turn over a log on tl320 no. 2 I smacked the gearshift lever onto a branch stub bending the gearshifter in against the cases and twisting it. Even after gaining clearance from the case no more shifting and stuck in 1st gear. The impact was more or less straight onto the end of the shaft. Is it possible that it maybe worked back out to get end float clearance? Or is it likely that a shock to shift drum may have stopped it working. The kicker is still working fine and I'm assuming the gear shaft is not bent in side the kickshaft due to this.

Any theories/ advice welcomed.

While ive got your attention my no. 1 bike is leaking gearbox oil and air into the crank - we replaced the clutch side seal - no good. Next step is to replace rotary induction o ring.

Heard a suggestion yesterday that there was a additive which behaves similarly to tire sealant and may force its way into the air leak and seal it off. Sounds to good to be true and Id imagine wouldn't be very clutch friendly??? anybody tried such a thing?



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Hi Reginald

Q1. Unfortunatley you will have to split that motor. There are only two ways I can think that the gearbox would jam up.

First one, is the selector barrel is located by a tensioner arm.....its the bit that locates it in position every time you change gear. Its possible to build a motor with this arm wedged behind the selector barrel (I have done this enough times !!), so I guess with a big enough hit it would knock the barrel and pop the arm.

Secondly, is that the shaft would probably bend at the weakest point, this being at the point it either enters or exits the kickstart shaft...so it would be possible that its bent inside, therefore allowing the kickstart to operate as normal, but not select any gears.

So, split the motor, I have plenty of decent used gear shafts if you need one.

Q2. Change the seals and O ring on the disc valve may sort the problem. Dont use any form of sealent, as the disc valve lubes the left side crank bearing and jamming that up with lube will create more problems than it solves. If not, you will need to split the motor and check out the cases. Its possible that the magnesium around the crank area has rotted away. Any water thats been sat in the motor will react with the magnesium, and I have plenty of cases that have rotted through where they have been left exposed to water. Alternatively, it may just require the centre cases sealing up, but will more likely be either seals or rot.

Let me know if you need any further help or explanation.



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