stock mufflers/headers questions. gray?

I've been thinking for the last few minutes about some experiment I want to do, & I have some questions. I've got an 07 wr450 with a 2006 stock yz450 muffler & a pro-circuit stainless header that was supposed to be designed for the 06 yz450. The bike has good power, but I'm always thinking of things to do to it. So I've got a practically brand new stock 08 header sitting in a box, that thing is way fatter than the PC header. So I'm wondering if I would benefit from modding the midpipe on the muffler to accommodate the 08 header. Would the larger diameter of the 08 header add low/mid/top power? or would it possibly rob power from the motor? Any ideas? I know the shorty 08 muffler is crap, but what about the header?

The '08 header is as big as it is to compensate fro the restrictive nature of the muffler. It probably wouldn't work out so well.

The '08 header is as big as it is to compensate fro the restrictive nature of the muffler. It probably wouldn't work out so well.

do you think the larger diameter would rob performance vs. the smaller header? If it was larger to compensate for the restriction of the shorty, how do you think the 06 muffler would react to it?

do you think the larger diameter would rob performance vs. the smaller header? If it was larger to compensate for the restriction of the shorty, how do you think the 06 muffler would react to it?

There would probably be less velocity using the bigger diameter header.

Poorly. The result would likely be a dip in peak with no corresponding gains elsewhere.

Thanks for the replies guys, useful information. It seems to me like I've hit a wall with the bike's power gains, probably would have to go with a HC piston to gain any more significant amounts of power. The WR already has all the typical mods, airbox, grey wire, jetted, 06 yz exhaust, 06 yz cams. Am I missing anything?

No offense, but why not just buy a YZ? Seems a bit more practical than trying to turn a WR into a YZ.

No offense, but why not just buy a YZ? Seems a bit more practical than trying to turn a WR into a YZ.

no offense taken at all, and not to be a smart @ss myself, but read my sig, I already have a yz. It's not that I'm trying to make the wr a yz clone, I just have the itch to make it run the best way possible, and it so happens to be that it resembles a yz in it's current state.

no offense taken at all, and not to be a smart @ss myself, but read my sig, I already have a yz. It's not that I'm trying to make the wr a yz clone, I just have the itch to make it run the best way possible, and it so happens to be that it resembles a yz in it's current state.

Ok, I can completely understand your constant need to improve your wr. If I had the money right now I'd be throwing every performance part on my 450 along with a port and polish lol. btw "Eats CRF450R's for breakfast and spits out their valves..." made me laugh.

btw "Eats CRF450R's for breakfast and spits out their valves..." made me laugh.

hahhaa, it's humorous and at the same time it pushes buttons with the honda owners. I came up with that last year after spanking some hondas on a couple of hillclimbs. The look on the guy's face was priceless when I beat him.

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