You can get a 58.5 kit with a higher copmpression piston . I put this kit on my red buggy and cranking compression went from stock 125psi to 145psi. Valve lash at .003intake and .005 exhaust. Made a good improvement but the port job was probally the most noticable. Also I tend to do more than one change at a time so the results are mixed together.
Before you do the piston kit I would get the 1500rpm torque spring and some 10 or 11 gram rollers. Scooter elements has a roller kit by oko with 12 different sets for 35 bucks!
That would be a great tuning tool for the money. Also if you like top speed keep the gearing stock and run 11 gram rollers. I have run 12 gram sliders and 11 gram sliders and keep going back to the 10 on the blue buggy. My red buggy has dr2 variator with 8/9 gram rollers and it hauls but but top speed is 31mph. I also got a A9 cam and am waiting for my stiffer valve springs before it goes in.
When you do the bigger bore kit measure the case opening because some 60mm kits will fit without boring, but the lower part of the sleeve is thin so beware.
I bored the case on the blue buggy this summer with a ncy boring tool and I will say it was not that easy because the tool would not line up the same every time and the power gain is worth it but a 58.5 or 60mm kit will work pretty good also.
Also remeber if you mill the head it will retard the cam timming a bit and could hurt the bottom end. Also the valves are closer to the piston. I had to shave off 15 thousandsth from the head on the 3mm stroker build becaust the timming chain was so tight the cam would not sit flush. I used a 1.6mm base spacer with 2 gaskest to get the piston to sit
.025 down the hole. And the first 62mm kit I got the piston was crooked, measured .015 on the chain side of the piston a .035 on the other side. I found a piston for 35 bucks on ebay and fixed the problem. The compression was 155psi and was slow to crank over.
So every major mod can have its problems. I Put a A12 cam in it and opend the combustion chamber a little more for the 62mm bore and the compression is now 145psi.
Now the motor runs strong compared to the stock cam. Just waiting for the valve springs for both buggys before we test them in the desert. Will find out if they stay together next month. I can only test drive down my street that is only about 50 yards or less. I have run it down the main street but am worried about getting run over.
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