Gas Gas ec 2006 1st gear problems

[Neil E.]

Originally Posted by Munch

Which shaft? The nut is moving the bolt it is screwed onto and not moving anything else. I really can't think of a way to get it off.

Shaft=Stud (hold it using a screwdriver after you slot it). Undo nut.

I don't know about the bottom unit in your picture, but the pin looks to be staked in place.

[Jakobi]

You have the shaft/threaded section and a small nyloc nut with a washer behind it.

You can either do as Neil suggested and try to slot the end of the threaded part so you can hold it while backing off the nut, or you can try and split the nut (cut down it in 2 places length ways) and peel it off the threads, or you can cut the whole nut and thread off entirely.

I'd suggest trying Neils. Once the nyloc nut is heated it should back off with very little force. You may even be able to zap it off with a few quick bursts of an electric impact.

[Munch]

So guys I got to work on the cases after figuring out the above issue.

First of all I noticed there was a lot less fragments/left overs than I expected if a cog had been damaged and ran for 90minutes+ like I thought it had.

Then I noticed something on one side of the crank, it looked like this:


I moved it with my finger and it became clear it is my woodruff key which has been damaged somehow, it looks like this out of it's seat:


I'm assuming that I'm missing part of the woodruff key and that has caused me some issues.
I split the bottom end and I got the gears out and they look perfect? I can't see any damage to anything, no grooves or anything where metal has been munched up between it all.

Gear videos:
1 - https://youtu.be/gGPcADGc-Hg
2 - https://youtu.be/Z_bmuXG6A4M

I know the lighting is bad but hopefully it shows atleast something. I'm not sure which gear cog is gear 1 but I have checked them all and can't see any damage but it's possible I am missing it.

If the cogs aren't damaged, is it possible that a piece of the woodruff key could have caused all of these problems while NOT damaging the cogs? That doesn't sound feasible to me.


Other pics as I'm not sure what I am looking for, do they all look ok?

[RockefellerGG]

How about some pictures of the gear selector and associated parts? When I first read your thread, my guess would have been to start there. If that key broke and has been rattling around in the crankcase, it would certainly cause issues, but I'm not sure why the issue would always be first gear. Was the key partially in the crank shaft still?

From what I can see in your videos, the transmission gear teeth look to be in good shape. How about the shift drum that lifts and drops the shift forks? This is the cylinder in the middle with all the shift patterns that engage the shift teeth.

Check out gears 10 and 20. These are the two that are meshed and under power when in first gear. Also inspect the pockets and inner engagement teeth that fit inside the gears when the shift forks slide them up and down and engage first gear.

[Munch]

Originally Posted by RockefellerGG

How about some pictures of the gear selector and associated parts? When I first read your thread, my guess would have been to start there. If that key broke and has been rattling around in the crankcase, it would certainly cause issues, but I'm not sure why the issue would always be first gear. Was the key partially in the crank shaft still?

From what I can see in your videos, the transmission gear teeth look to be in good shape. How about the shift drum that lifts and drops the shift forks? This is the cylinder in the middle with all the shift patterns that engage the shift teeth.

Check out gears 10 and 20. These are the two that are meshed and under power when in first gear. Also inspect the pockets and inner engagement teeth that fit inside the gears when the shift forks slide them up and down and engage first gear.

Yep it was partially in the crank shaft, it seemed to be been missing a slight piece that I guess is what was being thrown around the engine.

More pics!







I examined the gears further and I couldn't see any damage at all. It's going to be a disaster if I can't find what would cause this after having it all torn down.

[Neil E.]

The woodruf key is made of soft metal and is much softer than the gears. It is possible to have a small bit of the key wandering around without significantly damaging anything else. I would expect it to wind up on the magnet at some point. Based on the condition of your key I would guess that the crankshaft primary nut was not sufficiently torqued.

If a bit of key got stuck in the shift drum, it could prevent the pin on the first gear shift fork from travelling fully and this would prevent solid engagement of first gear. There is some uneven wear on your shift forks, but they don't seem too bad.

The gear dogs are on the sides of the gears. You need to remove snap rings and slide all the pieces off to really get a look at the mating surfaces. Do you know anyone with auto/truck gearbox experience? They could tell if anything looks suspicious.

With all of the shafts and gears assembled into one case half, you should be able to rotate them and watch the action of the shift drum, shift forks and gears. You need to verify that all related parts are moving their full distance when you engage first. The shift pawl also has to index the shift drum smoothly.

[Munch]

Originally Posted by Neil E.

The woodruf key is made of soft metal and is much softer than the gears. It is possible to have a small bit of the key wandering around without significantly damaging anything else. I would expect it to wind up on the magnet at some point. Based on the condition of your key I would guess that the crankshaft primary nut was not sufficiently torqued.

If a bit of key got stuck in the shift drum, it could prevent the pin on the first gear shift fork from travelling fully and this would prevent solid engagement of first gear. There is some uneven wear on your shift forks, but they don't seem too bad.

The gear dogs are on the sides of the gears. You need to remove snap rings and slide all the pieces off to really get a look at the mating surfaces. Do you know anyone with auto/truck gearbox experience? They could tell if anything looks suspicious.

With all of the shafts and gears assembled into one case half, you should be able to rotate them and watch the action of the shift drum, shift forks and gears. You need to verify that all related parts are moving their full distance when you engage first. The shift pawl also has to index the shift drum smoothly.

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?

Also when I removed the sump plug it was full of shavings, no actual hard pieces or anything like that. I think from the whole engine I've had one piece of metal that I could actually feel the rest of it has been very soft weird material or shavings.

If I put the gears back together into the case and they all operate fine is it possible I have been very lucky and it was the woodruff key all along? I am very worried about putting everything back together and still having the issue!

[RockefellerGG]

Originally Posted by Neil E.

The woodruf key is made of soft metal and is much softer than the gears. It is possible to have a small bit of the key wandering around without significantly damaging anything else. I would expect it to wind up on the magnet at some point. Based on the condition of your key I would guess that the crankshaft primary nut was not sufficiently torqued.

If a bit of key got stuck in the shift drum, it could prevent the pin on the first gear shift fork from travelling fully and this would prevent solid engagement of first gear. There is some uneven wear on your shift forks, but they don't seem too bad.

The gear dogs are on the sides of the gears. You need to remove snap rings and slide all the pieces off to really get a look at the mating surfaces. Do you know anyone with auto/truck gearbox experience? They could tell if anything looks suspicious.

With all of the shafts and gears assembled into one case half, you should be able to rotate them and watch the action of the shift drum, shift forks and gears. You need to verify that all related parts are moving their full distance when you engage first. The shift pawl also has to index the shift drum smoothly.

Some good advice here... Are the transmission case bearings in good shape? Before you do your final reassemble, it would be a shame not to completely clean these bearings and not reintroduce and metal fragments or shavings.

[Jakobi]

Few bits of swarf and fragments getting around in there.

I'd definitely be checking the dogs on the gears while you have it apart, as well as the transmission bearings.

To be honest, you've spent the time and effort to pull it down this far. You'll be into it a few dollars to get it back together already. Could be the right time to give her a big freshen up.

[(F5)]

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