WR 450 BIG BORE KIT TO 500

Anyone knows if there's any on the market?

thanks guys

You can get a 2mm overbore to make it a 472cc, don't know of anyone making them a 500 yet.

Dirt Bike magazine did a WR470 kit article and test last year and loved the results. I just cant remember the issue. I will have to dig for it.

I do know that yamaha has them (yz) :)

july, 2003 dirt bike mag. thumper racing did the set up for the article. it uses a 2mm over bore wiseco piston. also check; www.eric-gorr.com

he's been doing this kind of stuff for a long time.

Anybody know if the WR450 jug is compatable with the WR400 head? Or is this a possible swap with a complete top end?

Anybody know if the WR450 jug is compatable with the WR400 head? Or is this a possible swap with a complete top end?

??? If you are wanting the larger bore (95mm), I believe you should be looking for a 426 cylinder not a 450(The bores of the 426 and 450 are the same). The 450 is all different and is not compatible.

Right now I have a 426 jug on a 98wr400

it's bored out 2mm, so it's running 444cc I believe, 13:1

but if I want to go 500, can this jug be bored out 4mm? I thought that would be pushing it.

Right now I have a 426 jug on a 98wr400

it's bored out 2mm, so it's running 444cc I believe, 13:1

but if I want to go 500, can this jug be bored out 4mm? I thought that would be pushing it.

I don't think 4mm over is possible. I think I saw a 3mm over and they were having a hard time keeping head gaskets in it. You can go with a Powroll 2mm stroker for like a 469cc motor, YZDAD1 (SP???) did this. It requires a custom thicker base gasket to run with aftermarket and non modified OEM pistons. Talk to Cometic for the gasket, should be roughly 1mm thicker.

The 450 gets its extra CC's from a longer stroke, not a bigger cylinder bore. :)

Right now I have a 426 jug on a 98wr400

it's bored out 2mm, so it's running 444cc I believe, 13:1

but if I want to go 500, can this jug be bored out 4mm? I thought that would be pushing it.

I don't think 4mm over is possible. I think I saw a 3mm over and they were having a hard time keeping head gaskets in it. You can go with a Powroll 2mm stroker for like a 469cc motor, YZDAD1 (SP???) did this. It requires a custom thicker base gasket to run with aftermarket and non modified OEM pistons. Talk to Cometic for the gasket, should be roughly 1mm thicker.

The 450 gets its extra CC's from a longer stroke, not a bigger cylinder bore. :)

And doing this would put you within 3cc of an overbored 450. If you are looking for more, some custom head work and some hotcams may be in order. :D

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