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Old 03-25-2009, 11:30 PM
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Default 04 yz250 front sprocket removal

So I have been driving myself crazy with this all day, and I'm going to have a go at it tomorrow, just doublechecking before I break anything.

Is the big nut on the front sprocket reverse-threaded or anything? Nothing other than the chain/sprocket cover needs to come off right?
Is it fine to just sit on the brakes, instead of diving into the clutch and wedging something in between gears like the manual says?

And last, is the nut size a 32? That's what I'm using and it seems kind of loose, it looks close to 1 1/4" but I haven't tried it, and SAE would seem kind of wierd.
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Old 03-26-2009, 12:31 AM
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I have never worked on a YZ 250, but 32 seems HUGE for a front sprocket bolt. That's what size my rear axle nut is. A break-over wrench or even an impact might do the trick. [Only registered and activated users can see links. ] has it listed as "spec'l shape".
Btw, 32mm and 1 1/4" are the same.
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Old 03-26-2009, 01:15 AM
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It's big, I've been using my open end on the rear axle nut and it specs out at 27.
I tried using the open end on the sprocket nut, but it wasn't working. This sucker is tight, I've PB'd it twice, gonna let it soak down overnight too and hopefully a couple minutes with the heat gun tomorrow will loosen it up.
It's times like this that make my cry about my broken 20gal compressor. I have a 2 gal. mini and it just won't cut it for my impact gun.

Last edited by 808BMW; 03-26-2009 at 01:25 AM.
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Old 03-26-2009, 03:28 AM
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808BMW,

I have the same bike as you and just recently replaced my front and back sprockets. Anyhow leavethe chain on it and flip up the lock washer. I cant remember the size and am not near my bike to tell you but 32mm sounds close. Anyhow put the bike in first gear and apply the rear brake and crack it open. It should only be torqued down with about 30lbs psi so it isnt hard to get off. I dont recommend putting anything between the gears and crank case. In fact the manual states to apply the rear brake when you do it. Trust me it will come off if you apply the rear brake and it is NOT cross threaded, standard threading directions apply.


Cheers!

Ford
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Old 03-26-2009, 07:26 AM
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Ford is on it - good info.

The nut is standard thread direction.

Access to a pneumatic impact would dramatically reduce your stress over removing this nut - it would pop right off.

Scott
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Old 03-26-2009, 09:38 PM
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No matter how hard I stand on the brakes the wheel keeps turning. I tried strapping the tire to the pegs so it won't spin, but it still just lifts the rear suspension.
I weigh 205 and just can't keep the suspension down while standing on the brakes. I've heated it and used PB, and I'm using a 1/2" breaker bar with a pipe on the end. I really don't know what else to try, this sucker is tight.

Last edited by 808BMW; 03-26-2009 at 09:51 PM.
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Old 03-26-2009, 10:51 PM
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Did you bend the tabs on the washer away from the nut?
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Old 03-27-2009, 03:43 AM
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Quote:
Originally Posted by 808BMW View Post
No matter how hard I stand on the brakes the wheel keeps turning. I tried strapping the tire to the pegs so it won't spin, but it still just lifts the rear suspension.
I weigh 205 and just can't keep the suspension down while standing on the brakes. I've heated it and used PB, and I'm using a 1/2" breaker bar with a pipe on the end. I really don't know what else to try, this sucker is tight.
808, that is just bizarre but maybe the person before you locktited the nut which is not supposed to be and also as suggested in this thread did you unfold the flaps for the lock washer? It folds right over the edges of the bolt. There is also a circlcip type of locking measure too but i dont think they are on the 2004 yz250 or they arent on mine. At any rate make sure you remove the lock washer and unfold them or remove the circlips. Then here is the manual for removal and installation of the drive sprockets, hopefully it helps?!

removal:


install:


If this doesnt help you just might have to wedge a large screw driver or a tire iron between the sprocket teeth and the frame or engine but "BE CAREFUL". let us know how it works out for you!

Cheers
Andy

P.S. Sorry about my above post i quoted 30lbs psi and that was wrong, it is in fact 54 ft * lbs of torque for the nut
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Old 03-27-2009, 07:05 AM
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Good post, Ford!

PO - find an air impact.

Scott
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Old 03-27-2009, 11:52 AM
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Quote:
Originally Posted by MXtras View Post
Good post, Ford!

PO - find an air impact.

Scott

Thank you Scott, i do appreciate the compliment. I think you are right too, he is going to need an impact wrench to get that bad boy off.

Goodluck to you and i hope it works out!


Cheers!
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Old 03-27-2009, 03:45 PM
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Yeah the tab is bent flat. If I can't get it today I think I'll just give up and take it to my mechanic.

The sprocket doesn't even look worn much but I have new sprockets front+ rear with a new chain, I don't want to leave the old one on there and end up wearing out my new chain.
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