Jetting changes necessary for hop up kit?

5 replies to this topic
  • Bibleman

Posted July 23, 2007 - 06:21 PM


Hi guys, I'm thinking of installing the Hotcam (which I already have) and a HC piston. I have the stock carb with the complete Daves mods setup. Are further jetting changes generally necessary if I do this?

  • martinfan30

Posted July 23, 2007 - 07:32 PM


hey, im looking at the same thing. i want to do the hotcam and the hi-comp piston also. from what ive read you may need to richen the carb SLIGHTLY to make it work well. although i'm not positive, so lets get some more input!:excuseme:

  • cleonard

Posted July 23, 2007 - 08:47 PM


With the high compression piston it is a good idea to richen it up some. The reason is that the margin for error is reduced with more compression. The high compression also makes the engine run hotter. It is always best to start off rich and work your way leaner as you gain more experience with the new setup. As you must be close to sea level it is even more critical.

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  • Denn10

Posted July 24, 2007 - 10:40 AM


i agree with what cleo said what jetting is in it right now?

  • Kawabuggy

Posted July 24, 2007 - 01:43 PM


See my signature.. I have those parts installed already. As per my signature you can see where my jetting is. I am going up to a 160MJ for a weekend ride.

If you have changed the air filter to a higher flowing one, or have changed the exhaust you definitely need to go up on the jetting. Better to be safe, than sorry-I would start with a 68S and see how you like it. If the 68S makes it run too rich, at least you won't have burned the piston up figuring it out.

If you are going with a cam and compression, you need to have a better exhaust than stock. Those updates will really make the bike a beast. Enjoy.

  • Bibleman

Posted July 24, 2007 - 05:43 PM


Right now I have 55/160 Kehin jets and the FMF Q2 slip on. Jetting seems to perfect right now. I am assuming that part of the power increase is from the cam allowing a larger charge into the chamber. If it pulls in more air I'm guessing it would also pull in more fuel too??? Regardless, if I go this route I think I'll take the advise of going on the safe side and go one size larger on each jet and then take a plug reading.

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