mild port and polish w/stock bore

[GuavaJam]

What effect would it have on my powerband? I have everything else tuned nicely, liighter weights, center spring, clutch spring, aftermarket exhaust, up jet. Thx

[patthesoundguy]

What scooter is it btw? Where your powerband is depends on many factors. What pipe and what rpm range its designed to work in makes the most difference. Raising the exhaust port can really affect your bottom end as it can move the power band up into the higher rpm ranges. And I would first go and clean up the casting flaws and clean up the boost ports and transition and polish the exhaust and leave the rest of the cylinder alone at first don't raise the exhaust port right away. Especially if you have a stock carb. Ride it a while and see how it goes. You can't put material back once you grind it off and if the raised exhaust port doest jive with the set up you have it would be a real drag. Milling a few thousands off of the head may be a good plan to boost the performance especially in the lower rpm range. All in all a bit of porting where you have a pipe and everything is tuned already you should see a good boost. Just make sure not to over do the raised exhaust port.

[GuavaJam]

Thanks for the reply. I have a dd50 with 26 mm yms pipe. Not sure of the rpm range. What u just said is what a few guys told me. I definitely know how sensitive the ports r, so just wondering if its worth smoothing everything out, and what the gains would b. A few builders on here have said the difference is very small, and barely noticeable.

[patthesoundguy]

A dd50 is an af18 block isn't it? The trick is to get rid of turbulence all the way through the whole motor. So start with the intake tube and clean it up an make it cleanly transition and then rough it up like a cats tongue in side with a stone on the die grinder. Then clean up up the ports on the cylinder and make all of the intake surfaces rough like a cats tongue also. Try to have the smoothest transitions in the ports so the flow is smooth. You'll be surprised in how just doing that will get some better feeling response from the throttle. Better reeds will help as well. Bend the Reed stopper open until it just clears the case when you install the Reed block. That may give you a small gain in flow throw the reeds, every little addition to the flow will add up and may be noticeable.

[GuavaJam]

I believe its closer to the af16 with a few minor differences. Would bending the reed stopper compromise the flexibility of the reed itself. since it would be able to open up more? Resulting in less longevity? Or is this just a common reed mod that I didn't know about. Now I'm gonna have to research the best reeds when my stock ones are done, d***! lol. Just kidding thanks for all the help.

[patthesoundguy]

That small amount of extra travel on the reeds should be fine. If spree reeds hold up those newer reeds should too The cool thing is that there are so many options for reeds for that motor when you decide to get new reeds.

[maddog]

YMS pipes are made for bore kits not stock engines!