[mitchelldavis450]

hey guys I'm new to the site and have searched all over and couldn't find a similar scenario for jetting recommendations. I've got an 06 crf450r that i am currently rebuilding. the bike HAD a stock motor with a full fmf exhaust and stock (to my knowledge) jetting and seemed to run great.

i will be installing a 14.1 JE piston, stage 2 hot cam, hot rod crank with stock length rod and will most likely run on vp110.

i understand that i will need to richen up the jets and do some fine tuning later down the road but I'm not really sure what a good starting point would be. any help is greatly appreciated.

[Leardriver]

Start with a 165 main.

You don't need a richer jet. You just made the engine slightly more efficient with a higher compression piston, and the stronger carb signal will pull more fuel through any given jet than a stock engine.
I doubt that the bike will run as good as stock with that high octane fuel. It will produce zero detonation, but it burns too slowly.
Try 75% 91 octane pump gas with 25% 110 and see how it runs. These bikes run great on pump gas, but 14-1 is a ton of compression. You will sitting on top of a grenade.

[mitchelldavis450]

alright. never really thought of it that way. theres a few places around here that sell 100 octane. might give that a shot

[Leardriver]

That's a better idea. Still mix it 50/50 at most.

We all get caught up with the idea that bigger is better. More octane, more compression, etc, right up until we have a pile of melted parts.

Teams of engineers with virtually unlimited budgets made those bike with as much compression as they could safely run on, and added in a tiny little human-proof margin.
We should play around with the margin, without pushing it over the ledge.