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07 CRF250 - Broken transmission (3rd gear)

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I just had the 3rd gear on my 07 CRF250 broke (around 100 h on the bike), and was wondering if anyone had the same thing happened. I did my first crankcase splitting, and if you take your time, then it's not that difficult.

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While the motor is opened, I will change the crankshaft and some bearings (and piston, and cam chain, and ....etc). Are there any tricks I should be aware of (or special tools) to remove the crankshaft bearings (A on picture), and countershaft bearing (B on picture), or am I better off going to my dealership (or machine shop)? I tried to remove the torx screws (crankshaft bearing holder plate), and so far ... no luck.

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To get the screws out, you need an impact driver. It's pretty inexpensive around $20. I've been successful getting them out with an impact gun. It's not the best thing to do, but you can use an adapter down to 1/4" socket and put in the torx bit in the socket. A couple of quick jolts gets them right out. They also have loctite on the screws, so a little heat helps out.

I so far have not encountered any broken teeth on the gears. The dogs that engage the gears together is what usually goes bad, but they have to be replaced regardless. I not positive, but the 09 may have the same gears as the 07. They've been treated different in terms of process of hardning. It doesn't look like you have a choice in the matter, but you always replace them in pairs. The gears on the main shaft and the counter shaft both. Be prepared to spend a few bucks. They're not cheap.

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Thanks for the quick answer.

To get the screws out, you need an impact driver. It's pretty inexpensive around $20. I've been successful getting them out with an impact gun. It's not the best thing to do, but you can use an adapter down to 1/4" socket and put in the torx bit in the socket. A couple of quick jolts gets them right out.

I will definitely try this.

They also have loctite on the screws, so a little heat helps out.

Do I use blue or red loctite when I re-install these screws? Do I have to torque them really hard or the loctite will take care of it?

It doesn't look like you have a choice in the matter, but you always replace them in pairs. The gears on the main shaft and the counter shaft both. Be prepared to spend a few bucks. They're not cheap.

Yes, you're right, I have no choice but this is a good advice to change them both (mainshaft and countershaft) :bonk:. Each gear is around $50, so it's no so bad. I can't imagine how much I would spend if I was not doing this job myself !!!

Charlie C : thanks again. ALWAYS GOOD ADVICES FROM YOU ON THIS FORUM. :bonk:

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Being where the screws are at, I always use the red loctite so I don't have to worry about them backing out. Off the top of my head, I don't remember what the torque spec is, but make sure they are tight and the loctite will take care of the rest.

Before you think you're off the hook with only 2 gears, look at the dogs on the gears where they lock together. Not where the teeth come together. As you look at the gears on the main shaft or the counter shaft, where they slide together and lock into each other is where you'll find wear. The picture you posted that shows the main shaft 3rd gear, the 3 things sticking up off the gear is what I'm talking about. Those are called the dogs. They round off and effect your shift firmness. If they get bad enough, the bike can pop out of gear and you also can have whats known as a false neutral. My kids 08 did it after 80 hours. That was a $300 bill for the 6 gears I had to replace. Better to find this stuff now and replace them like that crank.

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WOW! that gear really got torn up. good slow winter project while you finish the season on the 450.... see you at etown... :bonk:

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See Billy, I told ya last Wednesday how badly that 3rd gear was messed up (maybe, I should shift sometimes! lol). I ordered all the parts and will get them soon so I can rebuild the motor (I love doing that stuff).

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good slow winter project while you finish the season on the 450....

Got all the parts Wednesday .... changed the crank, bearings, oil seals, transmission (3rd gear + fork gearshift), cam chain, piston (put an 08-09) ... like a brand new engine! Finish rebuild this morning .... started FIRST kick (not second, I swear! lol) .... I hate slow winter projects :ride:. I may still leave the 450 in the garage for a while.:smirk:

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I had the same thing happen to me, same year also. Be very carefull to clean everrything, especially behind the ball bearing that holds the small end of the main shaft. After the second time I took it apart I pulled that bearing and you could not believe the amount of metal Ifound there:bonk:. Replace all the bearings because those flakes fron the gears damage them

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my 05 blew the tranny end of 07. Had been skipping out of gear on the shift from 3rd to 4th, and i was trying to nurse it to the end of the season. Sure enough, last moto of the last race of the year she let go.

Broke 1 gear into bits, and chipped some other gears

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you can see the side loading force on the shift fork had made a mess of it too

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