DRZ400S big bore kit?

[BellevegasB]

Anyone here used or heard anything about the 436 and 470 big bore kits from Thumper Racing? Any performance specs? What kind of power increases each offers? And is the 436 a safer bet than the 470? Does the 470 bore the cylinder too much for reliability? Or the 436 for that matter? Any and all info is greatly appreciated!

 

[jodog]

I own a klx400 and looked into the bore kit, I havent found a lot of info on it but several people have told me the 470 is a bit risky because it can compromise the strength of your head. If I were going to do it i would say the 436 is plenty.

 

[beefking]

I would stay away from the 470 kit! Some people have had nothing but troubles with keeping the head gasket seal...there is hardly any room for the gasket to hold against. I'll be getting the 436 kit this spring; But the best way to do it is the Yoshimura 450 bore/stroker kit, mostly because it only increases the bore 2mm (with plating, not a sleeve) and alot of the power comes from the longer stroke. That route is also close to 3x the cost of a 436 kit.

 

[beefking]

Forgot to mention...the 436 kit will add low-mid power without sacrificing top end power or rev-ability much, but the 470 is slow revving and a torque monster. Of course the yoshi kit adds huge midrange and top end...it also increases the stock rev ceiling from 10k up to 11k and gives ya new cams. ;)