D
Deleted member 12676
Guest
At last! someone else into motocross!
I have rode a CR500 before and loved it. I wanted to buy it but didn't have the money at the time. I wound up getting an '89 CR250 and completely rebuilt it. I used to race motocross, starting on a Husky CR125 in Austin.
widening the ports increase power at mid and high rpm.
Expect 45mph as tops these can do without completely ruining the low rpm power. That's what mine does. But I cheat with a special torque pipe.
Click on my signature link and read about porting these engines.
Port the intake for a 120 degree duration and then raise the exhaust little by little (1.5mm) until it is as fast as you want it, then if it feels too weak on top (such as losing speed when going up a slight incline) then raise the transfers 1mm at a time till the top end is right and without ruining the low rpm power.
Put a good carburetor on it before you port, like a Mikuni 18mm. You will also need a Jaguar CDI and Iridium spark plug. You will also have to enlarge the balance holes in the flywheels.
I have rode a CR500 before and loved it. I wanted to buy it but didn't have the money at the time. I wound up getting an '89 CR250 and completely rebuilt it. I used to race motocross, starting on a Husky CR125 in Austin.
widening the ports increase power at mid and high rpm.
Expect 45mph as tops these can do without completely ruining the low rpm power. That's what mine does. But I cheat with a special torque pipe.
Click on my signature link and read about porting these engines.
Port the intake for a 120 degree duration and then raise the exhaust little by little (1.5mm) until it is as fast as you want it, then if it feels too weak on top (such as losing speed when going up a slight incline) then raise the transfers 1mm at a time till the top end is right and without ruining the low rpm power.
Put a good carburetor on it before you port, like a Mikuni 18mm. You will also need a Jaguar CDI and Iridium spark plug. You will also have to enlarge the balance holes in the flywheels.
