250 r chain/sprocket questions

[traxxasx]

We went riding today and my freind was riding his r the his chain popped off. Well i looked at it and its kinda too loose. So i looked and for some reason i couldent find out how to tension the chain. I was looking at the slide, the carrier bolts everything couldent figure it out since ive never dont it before. Also i checked out his front sprocket and its loose! Well the bolt is tight but the sprocket is loose on the shaft, i think its missing a spacer that goes behind the sprocket? Cause the shaft is say about 1/2'' and the sprocket is about a quater inch so its got some major play, where could i get the missing peices or does sombody have an extra i can get for free? Thanks guys!

[traxxasx]

wow i thought i would atleast have one reply, nobody tightens there chains?

[Red Rider]

All of the mind readers work late at the casinos. ;)

What year 250R is it? I've never tightened the chain on an 81-82 250R, but the 83-86 250R's use an "eccentric cam" chain tightening system. On those, you loosen the 2 pinch bolts on the back of the swingarm, then rotate the carrier backward to tighten, or forward to loosen, the chain.

[traxxasx]

All of the mind readers work late at the casinos. ;)

What year 250R is it? I've never tightened the chain on an 81-82 250R, but the 83-86 250R's use an "eccentric cam" chain tightening system. On those, you loosen the 2 pinch bolts on the back of the swingarm, then rotate the carrier backward to tighten, or forward to loosen, the chain.


Its an 85, yea i was looking and i figured that was the only way to do it but i had no allen wrench, also what is the bolt for thats in the middle of the to pinch bolts?

Thanks red rider.

[Red Rider]

That center bolt keeps the carrier from rotating beyond the chain-tightening limits. You be welcome!

[traxxasx]

That center bolt keeps the carrier from rotating beyond the chain-tightening limits. You be welcome!


Hey thanks alot. Now i need to find out hy the sprocket is so loose. It might be a sprocket off a dirt bike or somthing, as i remeber it goes bolt/washerplate/sprocket and thats all its loose!!!!

[traxxasx]

nobody knows about the sprocket?

[Mr. Sandman]

It sounds to me like the shaft or bearing is worn which is allowing the play you're seeing or if the sprocket is actually loose on the shaft and the bolt is tight, the bolt is too long and is bottoming out before tightening up or the splines on the shaft and or sprocket are worn.

[bigred1981]

Probably the splines man.. there's only one way to fix that.

[traxxasx]

Ok dont laugh at my drawing but i seriously did it in 1 minute to show you what i mean, the bolt is tight its tight to the shaft, the sprocket itself has like half inch plat like i can slide it back and forth. Like as it isent thick enough to acomendate the shaft. It fits on it but it seems like theres supossed to be a thick washer that goes behind it so it wonthave play and it would be tight? Take a look i can get real pics if you can understand my funky drawing.

[Red Rider]

When the sprocket is slid onto the countershaft, the sprocket should be flush with the end of the splined countershaft. If not, something is missing behind the sprocket, or you've got the wrong sprocket. The correct sprocket will be flat on one side, and have a raised edge on the other side around the splined hole.

[traxxasx]

When the sprocket is slid onto the countershaft, the sprocket should be flush with the end of the splined countershaft. If not, something is missing behind the sprocket, or you've got the wrong sprocket. The correct sprocket will be flat on one side, and have a raised edge on the other side around the splined hole.


Yes thats what im saying, the sprocket is no were near flush its got about 1/2'' play. So how thick is the sprocket supossed to be like a estimated guess, so i can see if he has a totally wrong sprocket on. Im sure it does. I will try to get a pic but i would have to borrow one of my freinds camera and then go all the way to my freinds house to get a pic lol. Thanks again red.

[Red Rider]

The sprocket is about 1/4" thick where the chain rides, and then the raised edge around the splined center is another 1/8" to 1/4" thick, so the total thickness of the sprocket where it meets the splined countershaft is 3/8" to 1/2" thick. These are just estimates, as I didn't feel like digging through my gear box this time of night to get actual measurements. I'm gonna go to bed now, good night. :)