Floppy chain on YZ 450s

I know a few guys with new 05 or last years 04 YZ 450. Seems like these bikes have the same problem no matter what year they are though. The bikes are almost completely stock(hard to believe, ain't it!). One of the few mods done to these machines has been to replace the stock rubber band chain with a real O-ringer for the trails. The new chains are slightly wider(a few millimeters) but I don't think the width makes a difference. The new chains do not hit the cases but they are carving up the subframe right above the swingarm. The chain has been tensioned perfectly according to the service manual and aligned too. The chain continues to saw into the subframe most noticeably in the off-throttle/cruising mode. Get on the gas and the chain stays reasonably straight. The chain appears to flop sideways too much and without more side clearance the damage continues. I know some chain slap is normal, but that is up and down movement, not side to side. What is going on here? Does the stock thin(and cheap) chain have to go back on the bikes?:naughty:

yup, all to common. Do a search for some fixes...or order a TM designs slide/glide plastic part to replace the stocker

I don't know how to break this to you, but neither of my 2 YZF's has a single mark on the inside of either the subframe or the frame itself, and both run hefty O-ring chains. To be honest, I haven't heard of the YZF having an issue with it (CRF's are apparently a different story), so I did a search and got 3 hits going back to 2002.

All YZ's from '97 up have a problem with grit under the chain slider abrading the swing arm ( here's my fix ), but if you adjust the chain by the book, align the rear wheel properly, and use a decent chain, they don't hit the sub, if when they're run loose. :naughty:

grayracer513, that is slick as heck...thanks for sharing that. You ought to mass produce that and make yourself some weekend riding money...

Two things. Number one you've got to make sure the slider is tight on the swingarm. Do something like Grayracer did or just use a fitted washer under the hat bushing that clamps the slider to the swingarm, that keeps it from moving. Then get some aftermarket axle blocks like Pro Circuit's. They provide much better rear wheel alignment and rigidity.

I don't know how to break this to you, but neither of my 2 YZF's has a single mark on the inside of either the subframe or the frame itself, and both run hefty O-ring chains. To be honest, I haven't heard of the YZF having an issue with it (CRF's are apparently a different story), so I did a search and got 3 hits going back to 2002.

All YZ's from '97 up have a problem with grit under the chain slider abrading the swing arm ( here's my fix ), but if you adjust the chain by the book, align the rear wheel properly, and use a decent chain, they don't hit the sub, if when they're run loose. :naughty:

?? I did a search and found many hits regarding this issue. I thought it was often recommended as a YZF "must do mod". Many different ideas on how to fix the issue. One guy suggested automotive goo underneath the chain slider.

My buddies had it real bad, tried JB weld underneath but that didn't work.

-oh and thx for tip regarding the axel blocks.

?? I did a search and found many hits regarding this issue. I thought it was often recommended as a YZF "must do mod". Many different ideas on how to fix the issue. One guy suggested automotive goo underneath the chain slider.

My buddies had it real bad, tried JB weld underneath but that didn't work.

-oh and thx for tip regarding the axel blocks.

We have to be sure we're talking about the same thing. The slider wearing into the swing arm is a for real problem. A lot of your responses seem to be focused on that.

However, the original post stated that the chain was swinging laterally and hitting the subframe, not the swing arm. That is almost always due to a misaligned rear wheel on a YZ. Under light loads, if the wheel points off at an angle, the chain will come off the rear sprocket headed somewhere besides directly at the front one. As it gets pulled back to the center on the way forward, it swings past center, then back the other way in a kind of whipping action. If it gets bad enough, it hits the mud flap or subframe. Getting the wheel in straight should fix it.

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