Thumper Racing 430 kit



4 replies to this topic
  • Rando400

Posted November 07, 2002 - 08:54 AM

#1

Has anybody tried the 430 big bore kit on their 400? I have been told by some local riders that boring the 400 creates problems and makes the engine unreliable. Any comments on this?

Randy

  • SFO

Posted November 07, 2002 - 10:45 AM

#2

the thumper kit utilizes a cast iron sleeve instead of nicasil plating.
I believe you can make a 400 a 420 and a 426 a 444.
There is reduced headgasket sealing area but proper assembly will yield a reliable machine.
My experience has been with the eric gore 444 kit and it uses a replated nicasil bore, BTW.

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  • ThumperWR450F

Posted November 07, 2002 - 02:32 PM

#3

i have a 97 suzuki DR350 that i put the thumper racing big bore kit in and made it a 435. about 2 weeks later it blew the bottom end. i wouldn't recommend getting any big bore kits cause it's gonna cost ya big time. just my 2 cents

  • Rando400

Posted November 08, 2002 - 06:02 AM

#4

Thanks for the info, I think that I will leave it a 400 and be happy it runs every weekend.

  • SFO

Posted November 08, 2002 - 06:34 AM

#5

This is my favorite part about my big bore kit in my 426.
Before and after dyno runs.

http://209.197.247.2...ne_yzf_ 444.htm



The extra ten hp on top is really fun for fifth gear wheelies and 15/42 gearing...
I got 50+ dyno runs on the motor and 1400+ baja miles without a single wimper reliability wise.

I got my stuff from

http://ericgorr.com/




 
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