I have a Rappy with a Trinity 686 Kit, Basically brand new. We cant seem to get this thing dialed in. Its Jetted 180/185 and Im running VP U4 fuel. I had been running a C12/93 pump mix. When I switched to the oxygenated u4, it seems to pull hard down low, but when it reaches about 6500 rpms, it just goes flat and wont climb anymore, kinda chugs a little. The bike had done the kinda the same thing throughout the RPM range when it was jetted lean on the racing gas mix, but now that Ive went up in jet sizes and switched fuel, I get this mess. Ive checked the CDI box, valves, everything. Im hoping someone else has experienced a problem similar to mine

Thanks Josh

 

I ran U4 in my raptor...to make it run right I had to up my main jet 2 sizes and one on the pilot screw. It ran awesome on that stuff. Its highly oxygenated and needs more fuel...well add more fuel and you get more O2...up your jetting again...richen up the needle one clip...I had the SAME issues I think I landed in the 192 187.5 main jet range

 

Thanks Jason, I have Jets through 200's coming.

 

higher oxygenated fuel actually leans your mixture, since there is O2 molecules that separate during combustion. so if you have it dialed in on non-oxygenated fuel, and switch to oxygenated fuel, your mixture goes lean, so upping the jet's should compensate. Likewise, if you get it dialed in on oxy fuel, it will run rich on non-oxy fuel.

good luck

 

Have you or anyine ever drilled jets...or know where you can get a set of bits designed to do so.