Sign in to follow this  
Followers 0
bluebreadtruck

Piston, cam, bigbore for 400?

6 posts in this topic

I have my wr timed to yz specs and love the top end power, however i would love to get some more mid/low power without loosing the top.

With my old 4 strokes, i would always add a highcompression piston and a cam, and maby bore it.

My question is with the 400, what is stock compression, and can i run a higher compression piston with pump gas?

would an aftermarkert cam set like a hotcam, etc really make a difference in power?

Do they make a big bore for an older 400 like mine?Is it possible to swap in a newer 450 cyl? thanks alot guys....been riding the bike stock and love it, but always looking for more power....ive been riding with streetbikes lol.

Share this post


Link to post
Share on other sites

check out this link. They offer a 400 to 426 with a bore change or 400 to 440 option with a bore and stroke change.

I was looking into this and didn't finish the research. I was thinking that if you only wanted to go to 426 you could buy a 426 jug and and a proper oversize piston for the 400, you might be able to do this without the crank/rod change. Maybe some else knows if the piston is availabe. This could save some cash.

http://www.powroll.com/P_YAMAHA_YZFWR426F.htm

Share this post


Link to post
Share on other sites

Yes you can because I've done it 4yrs and 5000 miles ago. Wiseco carries the piston 13.5 to 1. Stock is 12.5 to 1. I'm using a stock 400 head, crank and carb. Runs on pump gas all day long and man is it tons more powerful. I bought a stock WR 426 jug off of E-bay for $50.00 in great shape no boring needed. Jetting was nothing to figure out.

Share this post


Link to post
Share on other sites

OK, i just checked out my wiseco catalog

I see they make a 13.5:1 400 piston and 426 piston.

Could I buy a 426 or 450 jug(same 95mm bore), buy the correct piston and bolt it up?

Do all years use the same wrist pin size? I heard there is a cutoff year, but wanted to verify.

can you run 13.5:1 on premium?

Share this post


Link to post
Share on other sites

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
Sign in to follow this  
Followers 0