'06 YZ450 Jetting Question

Right now my bike runs great at 1500-3000 feet. I have a 165 main jet and a 50 pilot jet. This Saturday I will be riding between 8000-10,000 feet. I have the ZipTy fuel screw at 3 turns out. Is there enough adjustment to choke off enough fuel in the pilot circuit to leave it alone? I am thinking that I should drop to a 45 pilot if not. What about the main jet? The guy I'm riding with has a CRF 450 that he drops 5 sizes on the main. That would put me at 152. Does that sound right? Needle is in the stock position. Does that need to change?

Any help would be appreciated.

To correct for a net increase in altitude of 7000 ft, multiply your jet size by .94. That comes out 154, so a 155 should be right.

I cannot believe your bike runs well at all with such a rich idle circuit, however. Both my '06's run great at altitudes between sea level - 4000 ft with a 45 at about 1.75 - 2 turns out.

Either way, try the 45 for this trip. Needle will probably be alright.

Thanks for the info...where does the 0.94 come from?

I was surprised too. Its a first kick machine with moderate backfire on off throttle engine braking.

My pilot jetting steps are here.

155 main and 45 pilot worked great today. Not perfect, but good enough. Just because...I'm going to leave the 45 pilot in and see how it runs.

I bought the bike used, but I was never told that there was any flow / head work improvements. I cannot understand why the 50 pilot works either.

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