OK, first, all the issues I had initially when I put the 15mm rotary on, were instantly cured by an adjustment to the metering diaphram and needle valve, it loved that. As for the plastic manifold that came with the 15mm rotary, it has 2 seperate sets of holes, one has nuts pressed into the plastic, those holes bolt the carb to the manifold. The other set of holes (there might be 4 holes, but only 2 are used) bolts the manifold to the head (these go on first). As it turned out, these were only a few mm, like 4 or 5 too close together to bolt to the huasheng head. However, there is enough plastic around those that by drilling and some dremmeling, all the way out until the outside corners are as thin as you can get them, the bolts go in and go on. The sealing surface is on the inside, between the bolts, so it doesn't matter what you do to the outside, as far as those holes go. Also note that the carb doesn't sit straight up and down like this, the manifold will be twisted counter clockwise a couple of degrees.
Look at the manifold for the 15mm, look at it from the front where the carb goes on, the top left, and the bottom right through holes just need to be stretched out to the edge of the plastic, the corner of it. In fact, take the carb and manifold off the 4 stroke, and hold the two together, and you can see that those holes dont have very far to go.
And like I said, a tweak to the metering diaphram, and my 15mm started to sing like the fat lady, it runs awesome, now.
There was a tiny issue, and that is that at a couple of corresponding spots, there was just barely enough overlap of the different surfaces to make a seal the whole way around. I got sick of constantly buying new carb base gaskets, and then this, so I found a little roll of gasket meterial, and made my own gaskets, old shcool, like my daddy and grandpappy used to do back in the day. Being able to make a new gasket that took nnto consideration the difference in the shapes of the parts, and made sure that those got sealed good.
If you want to, me your snail mail, and I'll mail you some gasket(s) to expediate your project for you.
You know, come to think of it, I have a couple of those manifolds for the 15mm's floating around here, it only took me 5 or 10 minutes to do the holes out, I could do that for you, too, if you want, or dont have one to spare.
