2001 YZ426F Carb Rebuild

I recently purchased a carb rebuild for my 2001 yz426f. Everything looks like it was there EXCEPT the diaphram. I ended up putting the old diaphram back in, but I am not sure which way it is supposed to go. Does anybody know exactly how describe the correct position? Shoukd I have gotten a new one with my rebuild kit?


I ask because I had the bike running, but it ran terrible and the bike was sluggish off idle (before and after the rebuild). I tried adjusting the pilot screw (1 1/4 turn out) as per the recommended setting, but now the bike won't even start no matter what I do. Any ideas as to why the bike wont start other than a backwards diaphram? Really stuck here need some help. Thanks guys!!

The raised edge of the diaphragm goes toward the float bowl cover, not the apump cover.


This should have no effect on starting.


Clear the cylinder of unburnt fuel: throtle Wide open, kill button held down, kick a dozen times.


Try starting again, with no throttle.

Edited by KRANNIE

I haven't had my YZ long enough to know, but my WR REALLY hates old gas. It was idling lower on 3 week old gas. When I put it in, it ran fine. Let it sit for 3 weeks, it ran poorly. I hit reserve, filled it up, now it runs well again. At one point, on 2 month old gas (I got hurt), I couldn't get it to start. Since finding out that 3 weeks is enough to matter, I make sure to use fuel stabilizer and fill it all the way up (less air to help it go bad). 


I can't say that it's what your problem is, but I sure didn't realize how much mine cared. In comparison, my SV1000 fires right up on 6 month old gas.

I had to do an intake manifold on an S-10 once that cam e in running on a Monday.  It was finished that Friday morning, but wouldn't start.  We found that the gas had gone over the line during the week and was so bad that you couldn't even pour it on the floor and light it with a match.  But hey, the new fuel blends are good for the... something or other.

Slightly lower emissions at the expense of mileage, and they keep shops in business.

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