Yz250f rebuild - cam chain issues-

Alright so i'm putting a new top end in my 07, i shimmed the valves new piston, rings, clips all that and a new cam chain. problem is it seems as if its too short to make it over both cams, i can only get it over one wether it be exhaust or intake.

the tensioner is not even on the bike yet i cannot for the life of me get enough slack.

any tips or help? its the right chain and everything.

please help !

It may be possible that there are links trapped below the sprocket on the crank.

I've had two or three links fall below the sprocket and then the chain grabs both sides of the sprocket and the chain comes up short.

That does make sense, ill check tomorrow but I am almost positive its not hung up.

thanks for he reply I really appreciate it.

That does make sense, ill check tomorrow but I am almost positive its not hung up.

thanks for he reply I really appreciate it.

My pleasure. With the luck that I have been having lately, I have been getting a lot of hands on training with top ends due to the fact that I am rebuilding more than riding for some unknown reason that escapes me.

Kind of a win lose for ya, get good at rebuild but never ride haha. This is my first rebuild ever! did allot of studying and searching but i just got stumped on this.

Kind of a win lose for ya, get good at rebuild but never ride haha. This is my first rebuild ever! did allot of studying and searching but i just got stumped on this.

Not exactly, even when I had someone else do it, I've ended up having to do it all over myself again anyways - so basically, it was a lose, lose deal. Oh, you mentioned that your almost positive that it isn't hung up at the crank sprocket? If not, I always put my exhaust cam in first, then guesstimate where on the intake cam sprocket I should lay the chain before sliding/rolling it up and into position. It may take you two or three tries; but, that is only if the chain isn't coming up extremely short, then that is your alternative.

Edited by nokickstandsallowed

I started with the exhaust too, but i cant even get it near to being over the intake cam. How much slack is there usually? a video i watched just shows the guy tipping the cam down and it slide right over...

I started with the exhaust too, but i cant even get it near to being over the intake cam. How much slack is there usually? a video i watched just shows the guy tipping the cam down and it slide right over...

If it is that short with the tensioner being out and completely off the bike like you said, that leaves one of two possibilities: some links are trapped below the crank sprocket or the chain is the wrong one, which you said it cannot be. So, I'm banking on the first of the two possibilities. There is ample enough room, even with a brand new chain. About a link and a half easy free play slack if I recall correctly, because the tensioner still has to be put in like you stated, because you said that it is out or off of the bike. Your exhaust side guide piece for the cam chain may not be in the groove down by the sprocket either, but that is a shot in the dark as your cylinder head would not have mated easily with the cylinder but, would still go together.

If everything is installed correctly etc, and the chain links are not binding down at the crank sprocket (happens every time to me), then it's all technique to get the chain on the cams.

I install the chain on the exhaust cam first exactly where the cam need to be, then I tilt down the exhaust cam AND the intake cam to get the chain over the intake. There is not much room to play with.

I install the chain on the intake cam first, then take a Sharpie and put a mark 12 dots over so I know exactly where my exhaust cam should be. Then I tilt the intake cam while leaving the chain on and tilt the exhaust cam to get it on. Then just put them into place. It's really easy once you figure out the system. Goodluck

ok so i checked to see if the links are binding up, they seem to be fine. How would i fix it if they were? I still have zero room, i think all the technique in the world couldn't get the chain on because there isn't enough slack.

I tried tilting both cams and i can get the chain on both but they are almost touching, theres no way they would slide back into position....

I just leave off everything around the stator until I get the cams and chain back in, I make sure it's all in order then i'll pop that cover back on. (pretty much not what the book says but it won't make a difference) If you let ANY slack on the chain while putting the cams back in the chain will bunch up and can really jack that guide up if you turn over the motor. Good luck

ok so i checked to see if the links are binding up, they seem to be fine. How would i fix it if they were? I still have zero room, i think all the technique in the world couldn't get the chain on because there isn't enough slack.

I tried tilting both cams and i can get the chain on both but they are almost touching, theres no way they would slide back into position....

If it isn't binding, there is nothing to fix as far as that. However, visual confirmation from the side is your only guarantee that the exhaust side piece for the cam chain is fitting correctly in the slot for it. Unfortunately, removal of the items you had to remove before you put it on (cam chain) in the first place, is your only option at this point. I'm also starting to wonder if your intake side tensioner piece has the chain running correctly through it where it bolts to the motor.

Did you match up the old chain to the new chain and make sure they were the same length? It's not that easy putting the cams in. I had to put the intake in first and bolt it down a little then had to manuver the exhaust in. Was very frustrating

alright, Im going to take back off the flywheel and stator to see whats going on there, one question. how do you loosen and tighten the flywheel bolt without spinning the chain through. i do not have an impact driver. is there a way to hold it so i can break the nut?

alright, Im going to take back off the flywheel and stator to see whats going on there, one question. how do you loosen and tighten the flywheel bolt without spinning the chain through. i do not have an impact driver. is there a way to hold it so i can break the nut?

Type into the search feature in our forum: homemade tools, and it should help get you started. I've looked at a couple of them, but didn't see the good one I saw last month. I'll try to find you a link in the meantime:

Here is a good one to help you get started with some ideas: http://www.thumpertalk.com/forum/showthread.php?t=905863

I apologize, it wasn't in our forum, but if you use the search feature in the General Dirt Bike Forum, it will pull up even more. I believe I typed: Homemade flywheel holder.

Hope this helped.

Edited by nokickstandsallowed
ok so i checked to see if the links are binding up, they seem to be fine. How would i fix it if they were? I still have zero room, i think all the technique in the world couldn't get the chain on because there isn't enough slack.

I tried tilting both cams and i can get the chain on both but they are almost touching, theres no way they would slide back into position....

Take pictures if you can. It will seem very tight but it will work.

There's a couple good, informational videos.

You guys are Smart! haha it was bunching up every time there was slack, i found my old impact driver and pulled the wheel and saw it happening. Put it all back and it started 3rd kick!! Thanks for all the help! couldnt have done it without yall!!

Woo hooo!!! Glad you got it!!

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