Thanks Dx, but I can't quite picture it. From under the tranfer,
closest to exhaust, go down then up again to under exhaust port,
or sideways to under exhaust port? Also, how deep should the
finger ports be? 1-2 mm into barrel?
Another, easier thing you could do, to cool your piston, is rich up the MJ 1-2 sizes. So that it's running a little rich. I think that's an easier way for what you want. Letting it run alittle richer at WOT, doesn't affect the power that much (you won't notice it/only see difference on a dyno).
Sounds like an easier way to me
Also, how much mixture is going thru that port at 1,8ms, maybe you can widen it up..
Yes, richer would be better first step. I am running with a forced air
scoop, and 125 main jet (stock 14mm carb bored to 17mm), which
worked perfect in summer. I will try removing the scoop, keeping main
jet the same first. Hadn't thought of removing the scoop, it's been
there so long that I forgot about it.
I recalculated the time that a finger port to second ringland would be
open. 1.8ms is for transfer port duration, but ring land is only ~2mm tall,
which would make it's duration closer to 0.8ms.
As far as rejetting being easier, of course, but I like to make changes
to the cylinder. Have a new dremmel tool that I can't wait to try.
mopedadenyou, I've been looking at bore scopes on Ebay. Hope to get
one before summer, and a honing tool.
Also where did the piston seize. If you have a reed valve motor the inlet side of the piston can be cut to supply additional coolant to the top of the piston and top bearing.
If you have a good expansion chamber the flow will transfer because the exhaust will scavenge fresh fuel up thru the transfers.