Can I used a 150cc head with a 155cc cylinder?

DisillusionedPrepper · 01-11-2017, 04:36 PM

Hi,
Tire pressure makes a bigger difference in performance than the A9 cams do. Don't get me wrong but the difference is nominal at best but there is a small increase in top end breathing so you may get another mile or two in top MPH.
I put the A9's in every scooter I install cylinders on so there is a market for them.

Your head will work just fine with both the BBK, and the cam so no worries there. There is another new thread here (forgot which one but it's new/recent) where the fella is having an issue with the valves interfering w/ the piston on an A9 set-up.
You'll see in that thread that I suggested a possible cure, and reasons so DOUBLE check your adjustments before firing up the first time, and retorque everything after a short test run (a mile or so).

Jetting... No one can say. Go with the fattest jet to begin with, and jet down until you get what you need.
When you first fire the bike up do not expect idle to happen. Use the throttle to keep it at a mid-high idle, and adjust your mixture screw to allow a slightly richer mix. That means if you have an air screw (closer to the intake manifold) turn it in (clockwise) a quarter turn at a time until you get a good idle.
If you have a fuel screw (closer to the air box side of the carb) turn it out a quarter turn at a time to get a good idle.

The rest is all A,B,C's.
Lighter rollers?sliders, stiffer control spring, and stiffer fly springs in the CVT.
These are where the best bang for the buck come from.
For around 30 bucks you can gain a lot of take off torque, and a few MPH in top end.

Hope this makes sense, and helps.

01-11-2017, 04:36 PM	#2
DisillusionedPrepper Join Date: Dec 2016 Posts: 109	Hi, Tire pressure makes a bigger difference in performance than the A9 cams do. Don't get me wrong but the difference is nominal at best but there is a small increase in top end breathing so you may get another mile or two in top MPH. I put the A9's in every scooter I install cylinders on so there is a market for them. Your head will work just fine with both the BBK, and the cam so no worries there. There is another new thread here (forgot which one but it's new/recent) where the fella is having an issue with the valves interfering w/ the piston on an A9 set-up. You'll see in that thread that I suggested a possible cure, and reasons so DOUBLE check your adjustments before firing up the first time, and retorque everything after a short test run (a mile or so). Jetting... No one can say. Go with the fattest jet to begin with, and jet down until you get what you need. When you first fire the bike up do not expect idle to happen. Use the throttle to keep it at a mid-high idle, and adjust your mixture screw to allow a slightly richer mix. That means if you have an air screw (closer to the intake manifold) turn it in (clockwise) a quarter turn at a time until you get a good idle. If you have a fuel screw (closer to the air box side of the carb) turn it out a quarter turn at a time to get a good idle. The rest is all A,B,C's. Lighter rollers?sliders, stiffer control spring, and stiffer fly springs in the CVT. These are where the best bang for the buck come from. For around 30 bucks you can gain a lot of take off torque, and a few MPH in top end. Hope this makes sense, and helps.
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