Gas Gas ec 2006 1st gear problems

[RBrider]

Originally Posted by (F5)

You must check the dogs and the slots they fit into. The have to be square and not rounded even slightly.

I'd replace the first gear set and the shifting fork. The dogs only need to be slightly rounded and the fork slightly tweeked (bent) to cause the problems that you've described. (I had the exact same thing happen to me on a YZ 250 and a Buell streetbike, both times replaced the above mentioned parts with good results)

Then, by all means, do any additional upgrades or freshening up that might be needed.

Good luck with it. I'm sure you'll do fine.

RB

[Munch]

Originally Posted by (F5)

You must check the dogs and the slots they fit into. The have to be square and not rounded even slightly.

I think this may be the problem then? I have checked what I think is first gear and it's much more worn/marked than any of the others but I'm not sure if it's enough to cause me problems.




What do you think? Could this be my problem?

Originally Posted by RBrider

I'd replace the first gear set and the shifting fork. The dogs only need to be slightly rounded and the fork slightly tweeked (bent) to cause the problems that you've described. (I had the exact same thing happen to me on a YZ 250 and a Buell streetbike, both times replaced the above mentioned parts with good results)
RB

After seeing the above pic do you still suggest I replace the fork? It always shifted through the gears perfect with no problems.

Also in regards to freshening up I was thinking crank bearings and a new piston. What else should I be looking at? I don't want to spend a crazy amount of cash but don't want to shoot myself in the foot either. All transmission bearings and nice and smooth and luckily it seems there aren't many fragments.

[pscook]

I would replace parts 17 and 20, as 17 is the gear that drives the rear wheel when first gear is engaged. 10 and 20 are first gear, yes, but 20 free floats on the driven shaft and is always engaged with 10 (drive shaft) and will never, ever slip in its engagement with gear 20. 17, however, is pushed into the pockets of 20 when you select first gear, and if those dogs are worn, it will happily jump out given any opportunity. I have reasonable experience chasing transmission woes, and if this were my bike I would replace 17 and 20 as well as the associated shift fork.

[Munch]

Originally Posted by pscook

I would replace parts 17 and 20, as 17 is the gear that drives the rear wheel when first gear is engaged. 10 and 20 are first gear, yes, but 20 free floats on the driven shaft and is always engaged with 10 (drive shaft) and will never, ever slip in its engagement with gear 20. 17, however, is pushed into the pockets of 20 when you select first gear, and if those dogs are worn, it will happily jump out given any opportunity. I have reasonable experience chasing transmission woes, and if this were my bike I would replace 17 and 20 as well as the associated shift fork.

This is gear 17:


Does that look bad enough to be causing my problems?

[Munch]

Looking in the manual it shows ME25636008 x2 for gear 1-2-3-4 so do I buy both? Is there a way to see if they are worn because they are looking to be around ?50 each.

[pscook]

Originally Posted by Munch

Does that look bad enough to be causing my problems?

Yes. That and gear 20 are well worn, and the amount of wear indicates, to me, that those dogs won't stay locked together. As I'm budget conscious, I would buy exactly gear 17 and 20 and be done with it. I would also take my cylinder and piston to a reputable shop and have it measured before I bought a new piston. I would suggest at a minimum replacing the rings, but only after a thorough examination of the piston and cylinder. Main bearings? your choice, but they are easy enough to replace while you are in there. But then, in for a penny in for pound, right? If the bike is a keeper, might as well rebuild the whole thing. But as I said, I'm a cheapskate, so I would just do the minimum and get back on the trails.

[Munch]

Originally Posted by pscook

Yes. That and gear 20 are well worn, and the amount of wear indicates, to me, that those dogs won't stay locked together. As I'm budget conscious, I would buy exactly gear 17 and 20 and be done with it. I would also take my cylinder and piston to a reputable shop and have it measured before I bought a new piston. I would suggest at a minimum replacing the rings, but only after a thorough examination of the piston and cylinder. Main bearings? your choice, but they are easy enough to replace while you are in there. But then, in for a penny in for pound, right? If the bike is a keeper, might as well rebuild the whole thing. But as I said, I'm a cheapskate, so I would just do the minimum and get back on the trails.

Thanks!

I'm thinking of ordering:
Piston kit
Full gasket set
Gear 17
Gear 20
Woodruff key

My barrel is in really nice shape, no marks or anything that catch on my finger nail.
Piston:
http://i.imgur.com/3OZELKt.jpg
http://i.imgur.com/mJjNJSo.png

My current piston is a "B" (66.34mm), am I ok to just buy another one of that? I can't get an accurate measurement of the barrel and I don't know of anywhere I can get it done either.

[Neil E.]

Originally Posted by Munch

Now you have said that you reminded me of something. My uncle that had it before me rode it a few times since he had owned it and half way through his ownership it developed quite a loud noise, it would go slightly quieter when you would pull in the clutch and I was reading on the forum it could have been the primary gear nut. It makes sense it being that because it went away after 2 rides or so, could this have anything to do with it?

Quieter when you pull in the clutch is normal. A loose primary gear nut will create noise as a result of the backlash that happens. A loose primary nut will not usually create gear shifting problems, but chunks of metal in the oil can cause all kinds of problems.

[Neil E.]

As to the wear and rounding of the engagement dogs. The actual working face of the dogs is cut on a very slight back angle to help keep the surfaces fully engaged. It is the "wearing flat" of this angle that is the real problem. As a rule of thumb, by the time the corners of the dogs are rounded, the engagement angle is also lost. As others have mentioned those gears are due for replacement.

[Munch]

Originally Posted by Neil E.

As to the wear and rounding of the engagement dogs. The actual working face of the dogs is cut on a very slight back angle to help keep the surfaces fully engaged. It is the "wearing flat" of this angle that is the real problem. As a rule of thumb, by the time the corners of the dogs are rounded, the engagement angle is also lost. As others have mentioned those gears are due for replacement.

How do these look also?



And what do you think about replacing my current B wossner piston with another B? It seems really well seated and compression/power and everything else felt spot on, no marks on piston or barrel too.