This is an email i just sent out to someone from MA, figured I would leave it here for searches and to just get the information out…
So, the biggest differences in the Batavus cylinders (20, 25, and 30mph) are the Squish Band on the cylinder side (I think the 30mph is about 3mm and the 20mph is closer to 6mm)
The exhaust port size, the window is always the same. There is a cast in “nub” of sorts right where the exhaust port enters into the window, grinding that down effectively raises your exhaust timing when you get rid of it.
I believe the transfers are always the same.
The reed cage / carb is the same, but jetting changes.
And the other difference is the header diameter (26mm for slower bikes, 28mm for faster models)
The easiest way to tell what version your cylinder is is by header size, but it is also cast into the cylinder (1, 2, or 3) however isn’t stamped in the pistons like Puch cylinders are.
I think that’s pretty much it.. Hope it helps!
Also, MB5 got a fresh paint job while I was redoing some of the wiring and adding a taillight, I’ll post on that later though.
