3000' change in elevation, what should my change in jets be?

[SnowBigDeal]

I'm running 150 mains on my 35mm KEIHIN PWK's at 5500' elevation now. I'll be riding at 8500' elevation next weekend. Question is, how much leaner would you go when going from 5500 to 8500. I just want to be close, not exact. I won't be riding often at 8500, so I don't want to spend a ton of time fine tuning.

 

I was thinking of going down to a 145 main, but don't know if that will be too much or not.

[dajogejr]

I use a rule of thumb of 1 main jet for 1000 to 1200 feet, obviously each bike is different.

I'd say you're damn near dead on...

Don't forget, at that much higher of an altitude, your compression will be less too...less out of the hole.

If you have a timing plate, bump it a degree or to for some help.