Time to split the cases on the ole wr400. Worthwhile upgrade recommendations needed.

Well I'm pretty certain the rod & rodbearing finally exceeded their wear limit last weekend on my 99 WR 400.


The bike has a lot of hours/ miles on it. I want to freshen it up, make some good upgrades and get it ready for another decade or so of abuse.


As it sits the bike's current mods engine wise are : grey wire, yz timed, dr.d pipe, and airbox mods, and that's basically it.


The power on this bike has always been ok and it has been a solid runner. starts first kick unchoked stone cold and will go right to idle.


So basically I'm wondering what upgrades are recommended to be done while I have this thing torn down.


Here's what I had in mind.


have a new 426 rod pressed on the crank.


bore cylinder to 95mm.


13.5:1 weisco 426cc piston.


freshen up the head, most likely do some porting or at least port clean up (myself).


was thinking of upgrading the carb to something off a newer 426 or 450 (thoughts on this?)


should I change any bearings out?


should the clutch be upgraded for the increased power?


any other tips/ tricks/ suggestions?





Everyone out riding for the weekend or what?

Personally, I'd not invest the money and time in it and I'd get a later model for the better handling

Even if you replace every bearing and worn out part you are still gonna have a 15 year old bike with handling of a bike from the nineties

the al frame bikes were a good step forward in term of hanlding, over the steel framed 400/426/450 bikes


If you really do want to keep then replace rod, main bearings, any of the gears with pitting on the faces of the teeth, piston, rings & valve seals.

Sorry can't advise on the specifics, as I'm not that familiar with the 400/426 variants

Ya I want to keep it for sure.


The 6 hundred dollars or so for an overhaul is a small price to pay compared to scrapping it and buying a new bike.


Being as its plated in California makes it a pretty desirable.


I'm a pretty experienced rider and am not ashamed to say I've been passed hard by older vets on XR400s out on the trails.


A newer bike isn't going to make me get from point A to B any faster..... That electric start would sure be nice tho!



I actually have had 2 1999 wr400s. I love them. I still have one.

Have you heard of filing down the throttle stop?

I actually have had 2 1999 wr400s. I love them. I still have one.

Have you heard of filing down the throttle stop?


Yeah I've heard of that one, For some reason when I checked mine out it seemed as though the slide opened to it's full potential without any modifications.


When I do this overhaul I have been contemplating putting on a newer carb off a YZ anyhow.

Edited by TurboDon

Good to change the rod, iv seen a heap of wr 426 end up getting scraped after the rod failed, iv got one and they keep coming up on eBay in aus!

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