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TXT280 09 gearbox problem


cedec96
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At the very beginning I would like to apologize for my English. In my motorcycle, I have a problem with changing from 4th to 5th gear and from 5th gear to 4th gear, if I overgas it, the gear shifts. I've been driving like this for 2 years but now I decided to fix it. Can anyone tell me what could have been damaged?

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Are you saying if you are in 4th gear and give the bike a lot of throttle (gas) the bike will shift on its own into 5th and if in 5th gear it will shift on its own into 4th?

 

There is a known "clunk" and a little hard shift between 4th and 5th and back down from 5th to 4th, that is just a characteristic of the GasGas Pro transmission.

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@cedec96 First do this  https://youtu.be/G55FU27Z9bU?feature=shared  If that does not improve the shifting gear problem then you have to split the gearbox and check the bearings for wear that support the gear shafts then  check the (in english) dogs (teeth)on the gear disc/wheel  selector sliders and also the teeth of the actual gears themselves and the 'U' shaped selector forks need to be straight also. You need to check the selector drum slots for damage /wear and the 2x small  bearings on selector shaft. If you split the engine it makes sense to just change all the bearings in there any way while it is in parts it is not much money to pay . Good luck . Best wishes Alan.

Edited by Tr1AL
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If you look at that video. The shifter spring is held together by a piece of metal known as the top hat. There is a tab on it that can break and cause movement. You buy it complete with the spring. If that`s not the problem then one of the parts within the shift drum has broke. Which requires the cases to be split. 

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The top hat has a cross bar that acts like a fuse and is supposed to break if the shifter hits a rock then it won't shift at all and you replace that part without splitting the cases. Most likely the shift shaft is damaged and you will have to split the cases. The part on the shaft that breaks is a bicycle chain link looking part that holds rollers onto the shifting drum and you have to buy a whole shift shaft.

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yes, but then the problem would be with all gears, not only 4th and 5th gear, with the parts there is no problem because it is in my city where this part is concerned?

 https://trialsklep.pl/strona-glowna/1978-walek-dzwigni-zmiany-biegow-gas-gas-02-22.html

https://trialsklep.pl/strona-glowna/2487-rolka-zmiany-biegow-gas-gas-02-18.html

Edited by cedec96
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Your transmission has 3 shifter forks, shifter forks are made from soft cast material and prone to wear or bending.   Shifter fork 1./3.  Shifter fork 2./4. and  Shift Fork primary.  If only some of the shifts are a problem but not all, shifter forks is what I would inspect.

When a shifter fork experiences wear there will be an accumulation of metal particles in the oil when you drain it, (not likely to be magnetic) make it habit to dump your old transmission oil into a clear glass container and inspect it for fine metal bits.

 

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Being a Pro model. Anything is possible to be wrong inside. You are right wanting to fix it. A new transmission has to be quite expensive by now, or not available at all. I would pull it apart before any more damage happens.

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3 minutes ago, cedec96 said:

... on my free day I will start disassembling it, I will let you know what happened

Pictures, please!  I would love the see the actual gearsets from their "Four / Six system".  The patent drawings are not great.

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