Gearbox locks up...

[Wilmer]

Hello, I need help with my GasGas EC 125 05 that something have hapend with my gearbox...

I can't get it down to neutral or first gear, and it locks up in all the gears exept for second gear. I have split the engine to see if I can find the problem but can't find anything wrong except for a broken washer that i found all the pices for. But that doesn't effect the gearbox when the engine is split.

I took the gearbox out of the engine case to look at it more and everything is in good chape, cant find anything wrong with it.

Here is some pictures of it. It's very hard to get good pictures of the gearbox but I can take new pictures if someone needs. I also got a video but for some reason it doesn't work to upload it here...

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Very grateful if someone can help me

 

[Anders]

Wilmer,

I cannot get anything out of your attachments.
All links are "invalid attachments".

 

[Wilmer]

Anders,

Okey, I saw now that they don?t work. Im going to se if I can fix it









I also got a good video of it but can’t get it uploaded on the thread...

 

[Anders]

Now, the images are good. What exactly do you mean by 'lock up'? Doesn't the rear wheel rotate, or is it gear selection mechanism that locks up, making it impossible to select a different gear?

 

[gasgasman]

If the shift drum is " out of time", the transmission will lock up.

 

[Wilmer]

Anders,

The rear wheel locks up. You can change the gear but it can be pretty hard. And you cant get it in to first gear or neutral. When you get it in to a gear you can spin the transmission a little bit and then it binds up. And the same thing if you spin it backwords. It’s almost like it is a specific spot that lock up all the time. The higher gear you have the less you can spin the transmission before it locks up.

 

[Wilmer]

Gasgasman,

Okey, how can I look up if it’s out of time. And how do I adjust that? When I looked at it it seems to be right. All the shift forks is installed correctly.

 

[(F5)]

Well I'm not an expert but I'm pretty sure all those bits should be inside the engine. That might be the problem.

 

[(F5)]

It's not practical for most but I've seen people who cut a sacrificial case to load gearbox into. With one end unsupported it's a swine to drive through gears as they only have to skew a mm to bind.
You can then see how much engagement (which is what they were looking for to fight jumping out of gear) or check if gear selectors are bent a tiny bit. Check for telltale bluing or scuffing.
Have you swapped a selector around?

 

[Wilmer]

F5,

This happend when I was driving, I drove in 5th gear in 50km/h and then the rear wheel locked up.

 

[Anders]

Sounds like a gear wheel has moved sideways on its shaft. Are you sure that all your shift forks are in good shape? What about the shift drum? If both forks and drum (and their interconnections where the forks engages with the drum) are in good shape, I cannot really see how this could happen.

regarding the video; why don't just upload it to Youtube and give us a link?

 

[Wilmer]

Anders,

When i looked at the shift forks and shift drum everything looked good. I can take pictures of it later when i come home. I think I?m going to take the both shafts apart and look at the parts-diagram so everything is as it should.

Do you have a mail that I can try to send the video to?

 

[Wilmer]

I?ve now taken both shafts completly apart and everything looks good. No teeth missing, nothing bent or anything... I also looked at a picture from the partslist and everything is there and on it?s place.

But when I took the the shaft apart where the front sprocket is mounted on (sevendary axis) I couln?t get the last gear of. It is stuck on the shaft. Can that be the problem? Here is some pictures of it. The name on the last gear is ?SECENDARY GEAR II?







Im pretty sure that it doesn’t locks up in secend gear.

 

[Neil E.]

Your third picture is interesting. The bluing makes it look like that gear is friction welded to the shaft. Maybe someone who knows the 125 engine can comment?

 

[Zman]

Your third picture is interesting. The bluing makes it look like that gear is friction welded to the shaft. Maybe someone who knows the 125 engine can comment?

Good catch in the photo!

I think you have found your problem. That gear needs to be able to move on the shaft.

 

[Wilmer]

Yes, then that maybe is the problem... When I looked at the partsdiagram it looks like you are able to take the gear of. I just wonder if someone knows that it?s not a gear that is pressed on and is going to be stuck like that?

 

[gasgasman]

I don't believe any of the gears are pressed on.
They are either splined to the shaft or have a bearing surface.

 

[Wilmer]

Gasgasman,

Okey, then I will try to get the gear of it?s chaft. But I cant see how that can be the problem because that gear is on splins on the chaft so it?s not suppose to spin without that the chaft is spinning. But it?s the only weird thing I can find in the gearbox so that is maybe the problem...

 

[Wilmer]

Okey, now I?m pretty sure that that gear is the problem. At first I thought that gear had splines. But after looking at the partslist I can see that the gear doesn?t have any splines. And is going to be able to spin freely on the shaft. So I think that the gear have moved a little bit sideways and on to the splines and then locked up. Now I?m going to try to get the gear of and look if the shaft also is damaged and order a new gear. I will let you guys know if this was the problem.