Gas Gas ec 2006 1st gear problems
 

I picked up an gas gas ec 250 2006 and on my first ride my first gear was ok for around 45minutes and then I felt this weird "jolt" when I would give it some throttle in first gear, I guessed something had gone wrong with chain/sprockets so had a look, all looks fine.

I would give it around 20% throttle > jolt > release throttle > throttle again > jolt. That is what happens with slow throttle.

If I rip back the throttle then it will power > jolt > power > jump into neutral.

It seems like some sort of selector/shaft issue because it's only happening in first gear, I tried every other gear and they work 100% fine all through the RPM.

I rode the bike for approx 2 hours after I first noticed it and it didn't get any worse or better, if I ride slow I can ride first gear for a very long time which gives me some hope that the gears aren't mashed or anything.

Any suggestions?

Yes, strip that gearbox before it gets terminal.

That's a shame.. You just got that bike running how you wanted.

You're about to learn a whole lot if you intend to do it yourself. Luckily, Rockefeller just did his own rebuild and documented the whole process. I'd check it out if I were you.

Yes, it's a huge pain in the ass lol!

Luckily a bearing in the gearbox in my kx 125 destroyed itself a few months ago and I did that myself so hopefully this isn't too much different.

I am really tempted to get another ride in on Sunday before stripping it all down though and not use first gear. What do you guys think about that?

Your problem looks to with first gear only. There is another shifting issue to be aware of, but it is not specific to any one gear.
http://www.gasgasrider.org/forum/sho...selector+shaft

Before me a family member owned it and I remembered him saying when he would rev it hard in first gear it would jump into neutral.

When I was riding it for my first ever time (last week - 2 hour ride) I noticed while in first gear if I went to a hill climb or something similar which required a lot of RPM it would jump to neutral, I thought it could have been the gear lever on the case where it was vibrating so much so I changed it but no luck, still doing it in first gear.

The above has happened for approx 5 hours riding time, it was only today the "jolt" was happening. Does this provide anymore insight into what it could be?

What you are describing is often from badly worn engagement dogs on the gears themselves. Seen more on the higher gears on street bikes that are continuously "power shifted". The corners of the dogs round off and no longer hold engagement.

I'm not sure how you'd get this on a dirt bike unless a previous owner was in the habit of ramming it into first and spinning the rear wheel to show off. Clutchless shifting between gears on a dirtbike is works OK as long as the throttle is eased off during shifts. With good oil and reasonable care a gearbox will last for years.

The only other damage I might expect is a bent shift fork. That makes for difficult shifting, but doesn't necessarily make the bike jump out of gear. Looks like you will need to split the cases to find out what's wrong.

Unfortunately it's not something that will be able to be diagnosed from a computer screen.

You'll need to start digging. RHS engine case. Check the shift assembly and make sure everything is as it should be. Clicks through the gears. Springs are in place. No fatigued welds on the selector/acutuator. Check the shaft isn't bent.

From there it's only going to become a bigger job.. and I'd be inclined to agree with Neils thoughts.

Ever the optimist. Gears are incredibly tough. And bits of gear are still incredibly tough. So if you've lost some bits off the cogs and they are happily churning around in less than a litre of oil being flicked in the Maelstrom of churning gears and frothing oil. . . what happens if a little tooth decides to fall between let's say 4th and its mating partner?

I decided to drop the oil and the sump plug was full of shavings so I'm going to split the cases over the next few days and find out the damage.