Wacky 426 power

I have a 426 that I just rebuilt with a port and polished 400 head. And a wiseco piston. The valves have new seals

the power is weird, hardly any bottom end, moderate mid range, and crazy fast on top.

Im thinking its the clutch going out,

or could my carb be clogged from sitting around ?

or is it the 400 head?

tell me what you think

Check your Cam Timing?

funny thing is the reason my bike broke was the wrong timing. Im pretty sure it is correct now.

by the way, for all of you people who say bikes dont run on wrong timing....... yes they do. mine ran normally for four days.... it just sounded like it was pinging/knocking I thought it was the new piston. turns out it was the three intake valves smacking the piston in the face.

its not knocking anymore..... so it must be right:applause:

where did my low end go?

Are you yz timed? If so, retard the timing to get more low end...

I dont think it is yz timed. I timed it the according to wr426 manual.

Big-ass vacuum leak? That will sure cause what you describe...way too lean on the bottom to make any power, and then as the throttle opens up, the leak has less of an effect.

How did you cap off the vacuum port on 400 head intake port? Might want to spray some ether, carb cleaner or WD40 on it with the bike sitting at idle. If it's leaking and you spray some on it, the RPM should rise...

My first guess would also have been cam timing...it never hurts to double check.

The intake hole was tapped with a screw. I sprayed some wd 40 and nothing happened im pretty sure its not leaking, although the decompression lever is leaking oil is that bad ?

The intake hole was tapped with a screw. I sprayed some wd 40 and nothing happened im pretty sure its not leaking, although the decompression lever is leaking oil is that bad ?

Did you lube the cable? If so then ya it's ok to leak out... if not then, I dont know how else it could happen..

nope not lubed

I have experienced the same thing you are describing. It turned out to be the wrong cam timing. The intake cam was one tooth off. I can't remember which way it was off. but on tooth will make a big difference. If you have stock cams it is an easy thing to check.

Good luck!

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