crf450r Outlaw Go-Kart

[bluescionxa]

I have a 2003 crf450r motor. I've put a 490 athena big bore kit. Oversized intake & exhaust valves. A web Mysto Cam. Now I'm installing a Revloc clutch. This will all be installed on a Outlaw Go-Kart. I need help with what size Carb and the jetting size I might be looking to put in it. Any help will be appreciated.

 

[Masterphil]

What do you plan to run for fuel?
Compression Ratio?
Estimated RPM at peak HP?

 

[SFO]

who did the head?
What web grind?
Some of their grinds are very agressive.

 

[bluescionxa]

Masterphil, the fuel will probably be VP 108 or 112 (not sure what the track is allowing) Compression Ratio is 12.5:1 I'm estimating RPM at around 8.5K to 10K not real sure as of yet. Haven't got the motor to fire, so I can get it broke in.

 

[bluescionxa]

SFO, My brother in-law owns a shop in Oregon and did the head work. It's just a pretty simple port and polish. Web won't give out the specs on the CAM. It is the MYSTO CAM. Most agressive grind I believe. They said that it is what they recommended for the oval track, high RPM that it should be turning. I'm not to sure about the wide open thing yet. I'm just hoping for some decent horse power. First I have to get in the ball park with the jetting, also need to know should I have the carb opened. I believe it is a 40 mm FCR, should I go to a 41 or 42 MM. Thanks for the advice and Info

 

[Masterphil]

For a project like this, a dyno is your best friend. It will show you if your carb is too small for the cam and allow you to jet it spot-on for best power. I was mainly asking about fuel because I know most Kart classes allow alcohol. If the track allows oxy fuel, check out VP U4, if not VP C12 is also a good choice. At your compression ratio, you don't really need 108 octane fuel, these motors are very tolerant of low octane fuel. For comparison, I ran a 13.5:1 CR in my YZF and could run 93Oct pump with no problems at all.