Smooth that leading edge of your exhaust port out to help. You can read a whole post on it here.Įxhaust Port Chamfering: Fairly often when Polini’s seize it’s because the piston catches the top edge of the exhaust port and chips. Max Intake Porting: This is what I took my intake too in prep for the 24TM and Dio reedblock. You want to keep a smooth ramp maintained, so make sure to take your grinding all the way right up next to the cylinder wall like this. This is from the latest porting I did, so the ports are already taken back 2.5mm and have another 2.5mm marked. Recently I had my motor apart to prep and port it for racing this summer and took it back another 2.5mm. So how much is just enough? When I initially built my bike I took each port back 2.5mm. If you open these transfers too much you’ll hurt yourself.
A Polini’s torque comes from some wicked intake velocity.
Word of caution: don’t go nuts on these if you’re running a 2 petal setup. You can get some power by opening these up. Hookay, If you look at the intake on your cylinder you’ll notice the intake/boost ports are bigger on the cylinder wall than up by where the reed block rests. That said, if you’re ready, this is where things get fun. Intake Porting: A quick word on Polini porting: Don’t start porting if you have no idea what you’re doing. Some highlights.īrass sleeve inserts for a perfect case match and cylinder alignment.
Looking back I could have gone a little deeper towards the top of the case (making each trough a little deeper), feel free to.Ĭast Matching 2.0 A couple years after the initial case match I took the cases further. This is going to maximize flow though those transfers and keep your cylinder/piston cooler. Most all of this stuff exists in a thread or blog already, but I thought it’d be nice to compile it in one place.Ĭase Matching: Make sure you cut the top transfers from the Polini ALL the way back into the crankcase. There’s not much too it, but there are some Polini tips I’ve picked up from Devin at Motion Left Mopeds, Peter, the MA community and a few little things I’ve figured out along the way. There seems to be a lot of nervousness when it comes to building these kits.
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