new timing chain problem

I’m in the process of replacing the timing chain in my yz426.

The problem is that I cannot get the new chain on the exhaust cam gear.

I’ve spent 2 hour so far with no luck.:p

The chain tensioner is not installed!

It feels like the new chain is too tight/short

But it is identical to the old one! It is a Yamaha original chain 94591-50120

Compared to the old chain, they are of the same length and pitch, I measured before installing.

When I just removed the cams several times in the past, getting the old chain back on the cam gears was never a problem and took about 2 minutes or so.

Please advise

I just did the cam chain on my 426 last week and had the exact same issue. It boggled the mind. I also used an OEM cam chain that was identical to the old one except for a minuscule amount of stretch.

Unfortunately, I don't have any magic words of wisdom. I eventually installed the exhaust cam first keeping the chain tight between the crank and the cam before installing the intake cam. Its important to keep all the slack on the tensioner side. Even doing this it took me a while to figure out how to get the intake cam on and I can't give you a step by step on it. Just go slow, pay attention, make sure the chain is seated fully on the teeth of one cam before starting the next, and that all the slack is to the rear of the motor. It doesn't completely make sense, but to get the intake in, I had to put it in at a bit of an angle and rotate it down the chain into it's seat (after I had the exhaust cam already in place).

Good luck!!

Be sure you get all of that red shop towel lint out of there or it will clog up your oil screens. You should be using lint-free "paper" shop towels.

Just located the cause of the problem. It was chain slack at the crank.

http://img15.imageshack.us/img15/7795/slack.jpg

I had that exact same problem when putting together my 426, and it ticked me off until I pulled everything apart to check it out. New procedure for me: Timing plate goes on last, after cams are installed.

Be sure you get all of that red shop towel lint out of there or it will clog up your oil screens. You should be using lint-free "paper" shop towels.

Thank you for bringing this to my attention!

Also I'd like to clean the oil strainer and replace the oil filter after reassembly

Timing plate goes on last, after cams are installed.

You're absolutely right :p

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now

  • Similar Content

    • By PFOS58
      Lightly used Clarke Gas Tank (model #11614) for a 2010-13 YZ450F.  Includes cap.  For fuel injected YZ450F, so needs to have fuel pump transferred over.  Rest of stock tank hardware fits perfectly.  2.8 gallon capacity, so great for desert, hare scrambles, or WORCS.  Retails for $240.
      E-mail me with any questions or offers at billsworld@scinternet.net
      Buyer pays shipping from 84726.
    • By faizakhtar125
      Like this comment if you have a YZ. I want to see how many people have YZ's, especially YZ125's
    • By PFOS58
      ProMoto Billet KickIt kickstand for 2010-13 YZ450F.  Model 5006.  Used, but in good shape.  Buyer pays shipping from 84726.  Will take PayPal.
       
    • By PFOS58
      Used FMF Factory 4.1 Full Exhaust System. Includes slip-on muffler and two piece header.  Includes approved spark arrestor.  No dings or dents.  Fits YZ450F from 2010 to 2013.  You pay shipping from 84726.
    • By Christopher Harkins
      2009 YZ 250 for sale. Brand new top end, no hours on it. Pro circuit pipe and silencer. No trades. Selling for $3300.