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sprtrx300ex
07-10-2005, 06:41 AM
After my race yesterday I realized that the stock 400ex motor just wont cut it. What is the best way to go as far as MX racing... 416, 440....
K_Fulk
07-10-2005, 07:30 AM
http://www.exriders.com/vbb/showthread.php?s=&threadid=170595

I have everything you need right here. :cool:

People will argue all day long over what bore to use. But with that bottom end you could run any compression you want safely. And the cam and ported head will complement any bore you decide to use.
sprtrx300ex
07-10-2005, 07:39 AM
Is the motor still together?? Is there anything wrong with it, how many hrs? What are you asking for it?
FoxRacing81
07-10-2005, 09:26 AM
426 definatly. Faster then 416, revs faster then 440 and creates less heat.
K_Fulk
07-10-2005, 02:49 PM
The motor is still together, but I am going to keep the clutch, flywheel ,starter and side cases. Nothing is wrong with it. I'm just going bigger.

I have probly put 40 hours or so on it since i bought the motor. Don't know what it went through before that. But it still runs pretty good.
Dynoed 42hp last summer with an fcr carb and sparks pipe. The clutch was slipping then too so it may have a little more?