426 exhaust fitment? & GT Thunder

4 replies to this topic
  • bigtree123

Posted February 12, 2013 - 09:05 PM


Hey guys. Curious about what will fit exhaust wise on this 02 YZ 426. I hear some people saying up to 05 450 fits and others only 426.

Also GT Thunder. Does anyone know what they offer for the 426? This bike has a new jug with GT Thunder sticker and a spacer between the cases and jugs. IM also told it has a brand new crank. Enough of a spacer that the stock timing chain will not fit, even with no tensioner and the cams not bolted in. I am out of the country and cannot call GT that's the only reason I ask. I believe it has a new Weisco piston, I'll try to get a camera down the plug hole to get the numbers off it.

If it is a big bore or Stroker of some kind id imagine I'm going to have to richer it up abit, specially if I go with a full exh system.

Thanks for the time and space guys.

  • jojo1224

Posted February 13, 2013 - 10:16 AM


Sell me the engine, a spacer between the jug and cases usually means its a stroker. Measure the thickness of the spacer and multiply by 2 and that roughly how much more stroke. I wouldn't be surprised if its a big bore also.

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  • bigtree123

Posted February 13, 2013 - 02:16 PM


Apparently GT Thunder does not use spacers with anything he does on the 426. Now it gets interesting. If I wasn't 8000km away from the bike right now that might be ok. I think Falicon also makes Stroker cranks for these, any idea who else does? I just want to figure out what this thing has. Looks like I might be tearing it apart to see. Motor hasn't been run yet because PO couldn't figure timing chain had to lengthened.

  • jojo1224

Posted February 14, 2013 - 07:00 PM


Falicon, Crankworks, Powell (spelling?), those are the only ones I know about that still do them. It is also possible to make a 426 into a 450 using a 450 crank and a cylinder spacer and a 450 piston but that is a lot less likely to be done. Did you buy the bike in pieces? Your best bet would be to tear it down and see what has been done.

Edited by jojo1224, February 14, 2013 - 07:04 PM.

  • bigtree123

Posted February 14, 2013 - 07:21 PM


Bought it put together minus timing chain. I think I'll be taking it apart to see what's actually inside. Would be nice to know, especially for jetting, etc.

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