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I think my gearbox is mashed. Please Help!
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Posted by: thek---------------------

Went riding my 02 yz 250 f today and I noticed a clicking sound and I could feel it too.

I know my chain slider is wearing out so I thought it was just a bit of chain slap, yep no biggie. Anyway it continues to get worse until I pull over and take a look.

I put it in neutral and roll it, it rolls for a metre or so and then click its like the chain is getting caught up on something, roll it another metre then click again.

I take it home and now wheeling it around the back yard the click is a massive clunk with little clicks and the back wheel is stopping even.

Everything 'looks' fine, the chain isnt getting caught on anything.

What do you guys think it is?

Thanks

Posted by: biglou---------------------

Just a guess, but maybe you fragged a clutch plate? Timing chain is another guess, or the guide for it, if it was running ok. Just throwing out the simple stuff first.

Posted by: Ol'89r---------------------

Quote:

Originally Posted by thek

like the chain is getting caught up on something, roll it another metre then click again.

I take it home and now wheeling it around the back yard the click is a massive clunk with little clicks and the back wheel is stopping even.

Everything 'looks' fine, the chain isnt getting caught on anything.

What do you guys think it is?

thek.

What is the condition of your rear chain and sprocket? If the chain and sprockets are excessivly worn, the chain will try to climb up on the teeth of the sprocket for a few teeth and then bind and click back down. A new chain and sprockets should fix this.

Also, check your countershaft bearing. If the chain is adjusted too tightly, it can cause excessive pressure on the countershaft bearing and damage the bearing. The balls can fall inside the gearbox and do extensive damage to the gearbox. Grab the countershaft sprocket and see if there is any play in the bearing. If there is, DON'T ride the bike until you split the cases and replace the bearing.

We did a YZ426F for a local racer that heard a noise similar to what you are describing and went ahead and did several more laps at Glen Helen. We had to replace every gear in the gearbox except two.

Hope this helps.

Posted by: thek---------------------

Quote:

Originally Posted by Ol'89r

thek.

What is the condition of your rear chain and sprocket?
:

Chain and sprockets are perfect. I just did them about a month ago. Thanks for the other advice, I'll check it out.

EDIT; I just checked the front sprocket for play, and there didnt appear to be any.

I drained the oil and it looked really good, like dark brown. No fragments, no silvery glaze.

The click has got so bad that it completely locks up the rear wheel. This happens in neutral, and when in gear with the clutch pulled in.

This is starting to look really bad.

Any help info much appreciated.

Posted by: Ol'89r---------------------

[QUOTE=thek]
The click has got so bad that it completely locks up the rear wheel. This happens in neutral, and when in gear with the clutch pulled in.
QUOTE]

thek.

First you need to isolate the problem. Remove the rear chain and rotate the rear wheel and also the countershaft sprocket by hand. This should tell you if the problem is in the rear wheel or in the engine. Also, it will be easier to feel for play in the countershaft with the chain removed.

It still sounds like a bearing is starting to go. If your countershaft bearing or wheel bearing is starting to break up, most likely the bearing cage is broken. This is the little cage inside the bearing that seperates the balls. If this cage is broken, it will allow the balls to stack up against one another and bind. If this is the problem and you run the bike like this, eventually the bearing will break the inner or outer race. Then, you will have some serious problems.

Posted by: thek---------------------

Just a follow up if anyone is interested. It turned out that yes my gear box (second gears in paticular) was mashed.

4-5 teeth were stripped right off. parts were cheap enough, labour costs to split the cases cost a bomb.

thanks for the help/opinions guys

Posted by: 83MX80---------------------

ya thats what i thought it was too. a mashed tranny. it didnt sound like bearings. so is it all working properly now? are you back in the dirt?

Posted by: thek---------------------

Quote:

Originally Posted by 83MX80

ya thats what i thought it was too. a mashed tranny. it didnt sound like bearings. so is it all working properly now? are you back in the dirt?

Nah its getting fixed this week then I'm selling it so I can buy an 02-03 CR250.

The engine maintenance, which I can't do myself, has become too much of a financial burden, so its back to the smoker.

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I think my gearbox is mashed. Please Help!

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