yz426 rev problems

[iraq66]

i have a yz426 motor just got it all rebuilt. it ran fine for a few rides and then it seemed like it was hitting red line a bit earily. so i still ran it thinking it was just me.......then i went riding again was doing the same thing but hiting it alot earilyer...and my vaule cover gasket blew out.......so i changed the oil plug, fixed the gasket and went over all my wires.....start it up and go riding still doing the same thing......

so now it is at the shop.....its been sitting there for 3 weeks. 1 reason is b/c he things it is a drifrant wire harness....just for the fact there are a few plugs that go to nothing.....and the yz426 did not come with lights...that we know of. but im thinking it is the cdi...and that it is the 426 harness.

if anyone has any ideas please let me know. could there be a drifrant harness? if so what?

thank you
brent

[iraq66]

anyone???

[jrspawn]

It can be Alot of things really. Id say start with testing what you can. Test the stator and make sure you are getting the proper readings first.

Also you mentioned you blew out your valve cover gasket blew out. What happened there? Ive never had an issue out of any of the yzf or yfz engines valve cover gaskets. Just sounds a little odd.

Justin

[iraq66]

this is like the 4th time it happen. its like it has to much pressure in the head and it just pops out. i dont know why it keeps doing that.

but ill see what i can find out.

[Co_Racer]

Start buy doing a CYL. leak down test

[jrspawn]

Do you have the breather tubes on the valve cover or blocked off? It shouldnt be able to build that kind of pressure when properly vented.

Thank you
Justin

[jrspawn]

Pull the valve cover vent tube off and make sure its not blocked, got alot of gunk in it, pinched anywhers, and routed without any sharp bends. More than likely this is your issue with the gasket blowing. Ive had other YZF and yfz engines with almost unreal amounts of blowby and never had this issue. Also have you replaced with a new gasket and are you using any type of sealant on it?

Thank you
Justin

[ss440ex]

Originally posted by jrspawn
Do you have the breather tubes on the valve cover or blocked off? It shouldnt be able to build that kind of pressure when properly vented.

Thank you
Justin

The small dia hose top front of the rocker box must be free and clear.....
Should be vented back into the oil tank.

I`ve also seen it cause lots of problems.

Sounds like you need a manual for the other wiring issues.
Make sure all wire are connected where they need to be....there`s not many.

Good luck,
Keep us up dated.

[iraq66]

the tube is clear i even pulled it off to see how it runs to make sure thats not it.....

as for the wireing could be it a drifrant haress? like a yfz450 or no?

could it be my cdi???? im just trying to get it down to a few things. im going to pick it up tomarrow and do it my self he has had it for way to long

well thanks guys

[ss440ex]

Stator maybe going bad...