big gun over rev box

5 replies to this topic
  • majesticwoods75

Posted July 14, 2007 - 05:59 PM


I have an 06yzf450. I have a full yosh exhaust hot cam and a 13.5 high compression piston. I notices when I put a big gun over rev box on it will not pull hard in third gear or under load. Take it off and the same thing. Need some help do i have somethng wrong in the motor or is the cdi boxes shot

  • KJ790

Posted July 14, 2007 - 06:45 PM


Sounds like it could be jetting. Did you rejet when you added all of the mods? My experience is that when you add a pipe and hotcams you need to lean your jetting. When a fourstroke is running rich it feels like it won't pull hard.

  • majesticwoods75

Posted July 14, 2007 - 06:49 PM


I have rejetted, I have gone down to a 160 and it gets hot and I have also gone up to a 170. Feels like the same power through out.

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  • KJ790

Posted July 14, 2007 - 07:01 PM


Well then start with the real basics and work your way through. Make sure your CDI is plugged in all the way (since you were messing with it maybe it isn't plugged in right). Make sure your spark plug cap is pushed down all the way (Yamaha's have a nasty habbit of working their way up and losing spark). Try changing the spark plug. It doesn't sound like your timing is off, but you can check to be safe. Then you can start getting more technical. Check your clutch to see if it is slipping. This happened on my 250F when I did a bunch of mods like that the bike stopped pulling and it turned out that the clutch springs were not strong enough and the clutch was slipping (I wasn't getting extra enplay though which through me off). Then you could try a compression check.

  • majesticwoods75

Posted July 14, 2007 - 07:28 PM


Thanks for the info I took it a mechanic here the one that did the mods for me and he is baffelled to what to help me with it good to have another head in the game.

  • KJ790

Posted July 14, 2007 - 07:32 PM


Keep us updated as to what you do and what you find.

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