[Hpc0507]

Currently stock piston running 135 main 45 low with baffles out and power up needle in third notch. I just pulled the engine apart after my timing chain tensioner failed and the chain came off and piston popped the intake valve. I'm installing BBR valve springs, Outlaw stainless valves, Tokyo manual tensioner, new timing chain and a wiseco 11:1 piston. Can anyone point me in the right direction for jetting with the increased compression? Thanks in advance

[JimDirt]

Welcome to the site !!

Hopefully Ray (he is the resident 230 expert) or Leardriver (he is the resident jetting expert) will chime in and get you on the right path ... They will need to know your elevation , to give a accurate recommendation ..

[Hpc0507]

Welcome to the site !!

Hopefully Ray (he is the resident 230 expert) or Leardriver (he is the resident jetting expert) will chime in and get you on the right path ... They will need to know your elevation , to give a accurate recommendation ..

Thanks elevation is around 700-900 above sea level.

[Aussiecrf230]

Well I am a little surprised you can use the 120 main with the power up needle C30F. So I have to guess you are at a higher elevation, is that correct?

In my experience increasing CR actually makes the the induction pulse a bit harder so it will suck more fuel for the same jet size. Similar to going to a big bore and it sucks harder on the carby as well.

Not saying that changing jet size or clip position may not prove worthwhile but not by huge amounts.

If you thinking of modifying head or a cam change you are physically go to get more air in so will need more fuel.

[Hpc0507]

Well I am a little surprised you can use the 120 main with the power up needle C30F. So I have to guess you are at a higher elevation, is that correct?

In my experience increasing CR actually makes the the induction pulse a bit harder so it will suck more fuel for the same jet size. Similar to going to a big bore and it sucks harder on the carby as well.

Not saying that changing jet size or clip position may not prove worthwhile but not by huge amounts.

If you thinking of modifying head or a cam change you are physically go to get more air in so will need more fuel.

Thanks, makes sense. So I was mistake on my jetting. I'm 135/42 at the moment. Honestly wanted to go a bit lower on the low side as I still picked up a rich lag on throttle but this hot summer it seemed ok. I will still with my current settings and try to read plug after a little break in period. Thanks again

[Aussiecrf230]

I have found the 132 is a bit rich in summer and would probably run better on a 128.
I don't bother changing it as a little extra fuel helps keep piston cooler when the aircooled engine can't get rid of the heat.

Just right when it is cold though.

[Leardriver]

When 450's were in Denver for the MX race years ago in the carb days, they ran a main jet 2 sizes leaner than we normally would based on dyno measurements. The idea was that the ported heads, big cams, and high compression engines made the bikes a more efficient air pump, and therefore pulled more fuel through a given jet.

The point is that you don't necessarily need a different jet when you raise compression if you were right on to begin with. The main jet is more for constant wide open throttle anyway. Drivability is more related to the pilot and needle.