xr650l piston comp question

3 replies to this topic
  • sweetk30

Posted August 12, 2006 - 02:37 PM


i have been reading about hot cam & big comp bigbore kits all together. the hot cam from what i see eliminates the decompression kit. and the 10.5:1 pistion kits with the cam make it hard to start when hot even for the electric start with good fresh battery.

so i was thinking what if you milled down the dome of the pistion to drop it a few points like 9.5:1 compression . would this help and or do thay make a pistion like this.

added: or get a custom pistion made as some offer to do for about the same money.


Posted August 13, 2006 - 02:23 AM


milled the piston? not a wise move.

better to add one more gasket to raise the top a little, thereby reducing the compression ratio.

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  • zodran

Posted August 13, 2006 - 05:18 AM


My megacycle cam retains the auto decompressor, but you have to use hardened rockers. I also had to send my stock cam as a core. I've never had a problem starting hot or cold, usually get 3 or 4 years out of a battery. :thumbsup:

  • sweetk30

Posted August 13, 2006 - 06:14 PM


some on other threads and sites have stated thay the hot cam and the 10.5:1 together with out the decomp is hard to start when hot. i plan on keeping this street and trail. but figured when apart to fix the problems i would just bump it a bit. i just dont want to make a big mistake when its all said and done as i have the few extra buck for the mods but i dont have the money to rework it if its a big upset.

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