1999 WR400 Big bore kit or a 426 cylinder


8 replies to this topic
  • acarter92

Posted February 16, 2009 - 02:13 PM

#1

I'm soon getting ready to do a complete rebuild top and bottom end. Although it has enough power it wouldn't hurt to have a little more. I did some forum searches and didn't really come up with anything. Does anybody know if it's possible to put a wr426 cylinder and piston in it. Are they compatable, would I need to get a 426 connecting rod too. Also, is a big bore kit available for my bike? Just looking for options.

Thanks,
Austin

  • 123BigcoopDawg576

Posted February 16, 2009 - 08:08 PM

#2

Does anybody know if it's possible to put a wr426 cylinder and piston in it. Are they compatable, would I need to get a 426 connecting rod too


the answer to both your questions is YES...for more detail, search under the user name "Birdy426" as he is the man when it comes to the 400/426. :lol:

  • 02WR426Cali

Posted February 16, 2009 - 10:34 PM

#3

I think at minimum you need the 426 connecting rod as the pin diameter is different, and a 426 cylinder. But unless you can find a good used cyl for cheap it might be best to check out lukesracing.com and get the 444 kit.

  • acarter92

Posted February 17, 2009 - 03:33 AM

#4

Ok, I'm going to check out "Birdy" tonight (I have to go to school now). One of the reasons I want to do the 426 mod as oppossed to a big bore is reliablility. I don't want to compromise how greatly reliable this bike is.

Austin

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  • Just_a_trail_rider

Posted February 17, 2009 - 07:56 AM

#5

I'm soon getting ready to do a complete rebuild top and bottom end. Although it has enough power it wouldn't hurt to have a little more. I did some forum searches and didn't really come up with anything. Does anybody know if it's possible to put a wr426 cylinder and piston in it. Are they compatable, would I need to get a 426 connecting rod too. Also, is a big bore kit available for my bike? Just looking for options.

Thanks,
Austin


Austin,

Why fix it if it ain't broke? A good running bike with "enough power" as you stated just needs to be ridden harder. Twist the wrist...

Nowadays, yz426's are going for about 2K or sometimes less for people who really need money. Why not just invest in a different bike that already has additional cc's and power?

btw... I've ridden wr400, 426 and also own a 450. I would not be looking for too much more power from them. The cost per additional hp gets really expensive at some point.

  • acarter92

Posted February 17, 2009 - 03:17 PM

#6

Austin,

Why fix it if it ain't broke? A good running bike with "enough power" as you stated just needs to be ridden harder. Twist the wrist...

Nowadays, yz426's are going for about 2K or sometimes less for people who really need money. Why not just invest in a different bike that already has additional cc's and power?

btw... I've ridden wr400, 426 and also own a 450. I would not be looking for too much more power from them. The cost per additional hp gets really expensive at some point.


What you say makes sense. But, it is broke :-) I hit a rock a while back that went through the skid plate and broke the case where the oil drain bolt was. I had a professional welder weld it the best he could, but it still leaks more than I would like (even with JB weld all around his weld) I have a spare case sitting on my workbench ready to go on. I put at least 200 miles a week on this time a year and more in the summer. I work to ride :-). I'd really like to get this issue worked out before summer when everybody else rides too. I think it's not to far from taking a sh$$ because just since last year I have over 3,000 miles on it and I know the guy before me rode it alot. It's also burning a little oil.

The more I think about it the more I'm thinking I'm just going to rebuild it and keep it as a 400 though. I'm all about reliability. I sometimes ride alone and really get out there in the bush. The bike really does have plenty of power, I go through tires, chains and sprokets way faster than I'd like and adding more power is just going to make that worse. I do think that if I could get ahold of a 426 cylinder and connecting rod pretty cheap I would go for it. I could re-sleeve it and really wouldn't be out much more than just rebuilding my 400.

Austin

  • 02WR426Cali

Posted February 17, 2009 - 05:27 PM

#7

I think the 426 is even more reliable due to the bigger piston pin being bigger. They made it bigger to be more reliable from what I've read

  • Birdy426

Posted February 17, 2009 - 11:11 PM

#8

I think the 426 is even more reliable due to the bigger piston pin being bigger. They made it bigger to be more reliable from what I've read


First, BigCoopDawg, thanks for the props, but there are lots of folks on the boards here smarter than I am.

I was going to respond the same way here...the 426 got two improvements over the 400 in the crank department. The first was the bigger "small end" bearing, and the second was the splined primary gear as opposed to the keyed gear on the 400s. Both were to improve durability. When I went thru my motor, the cost of a rod kit and the labor to split the crank, reassemble and rebalance was very near the cost of a new crank from the TT store, so I went that way (your mileage may vary depending on location and who you know...)

I took my 426 out to a 444 and was amazed at the increase in bottom end that 18 cc's made! (of course, that may have been helped by the 13.5:1 compression). You could do the same to your 400...send your 400 barrel off to Luke's Racing as a core and get whatever size you want.... When I went thru my motor, I needed to either replate and hone to size or go big bore. I was out of round, over taper, and just a bit on the big side of the bore. Again, it was really a push cost-wise to get my barrel replated and honed, along with a new piston kit, or go big bore. As there is no replacement for displacement, I went big.

The bottom line is it depends on the condition of your motor...If your rod bearings are nice and tight at both ends , the keyways aren't worn, and you trust the whole bottom end, you have a couple of options...first, if the bore is also in good shape, just run a glaze breaker thru it, put in a new piston kit ansd press on with pride (assuming the piston checks bad..rings if it checks good...I would change it anyway, myself, just to be safe. You can't always see, and certainly can't measure cracks). Second, if the crank (really bottom end) is good and the bore is bad, Luke's has a big bore kit that takes the 400 out to...I believe 420 cc's...and may be a push cost-wise to having your stock one reworked. The guys at Lukes and Eric Gorr both really know their stuff, and have said that they really have no reports of early failures in the 400s or 426's with big bore kits. Finally, if the crank is a bit on the loose side and you have to replace the rod anyway (along with the piston and barrel), I would look seriously at installing a 426 crank and doing the 444 mod. If you go with a 426 crank, you will also need the primary gear. Be preparred, though...if you do need to do that much rebuild, you're probably looking at a grand in parts...

  • acarter92

Posted February 18, 2009 - 03:32 AM

#9

Thanks Birdy,

Right now (before I got a bigger cc in my head) I was planning on spending about $1,000 all together and that's top and bottom end rebuild with all new oil seals and gaskets. I still got a lot going through my head and am not sure what I'm going to do yet. Right now the bike is still running so I'm in no big hurry, but as I said before I do want to get it done before the warm weather hits and I expect this to probably take over a month for me to do. If I had all the parts sitting there I could probably do it within a couple days (when I start something I finish it), but I know that I'll need parts that I forgot to order and have to wait for them to come.

Austin




 
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