Oops, I used it to clear the exhasut had to file the left corner very slightly to get the exhasut to fit. Everything else fitted alright, was tight but no issues? Shouldn't cause an issue m should it? Thanks for spotting anyway.That gold head is not on right, the flat spot is to clear the coil, if that clears your coil its ok.
So explain your theory on NOT posting the exhaust??? You are not making any sense, considering others on this forum have proven some of the things I perceive you are saying.Chrisi is correct about the boost port direction, it should be aimed toward the spark plug. Also boost port height should be the same as main transfers. There is some debates that boost port should be slightly higher so it would help to start the scavenge loop upwards.
The main transferports in stock shape are also terrible in this respect. If you look at it, they have an abrupt angle which seems to be about 90*. They should be pointing slightly upward, following the curvature of piston dome. But it is hard to fix this by grinding because the transfer port roof cannot be raised, it will rise the duration too much. One way is to fill the corners with epoxy.
Edit: some more ranting... about the exhaust port. Enlarging the exhaust duct and making the pipe side outlet larger is a mistake. This will enlarge exhaust duct volume and rob energy from the initial exhaust pulse. (although this matters only when using a tuned exhaust pipe).
It will also slow down the flow when the area is made larger. I'm not saying exhaust port shouldn't be enlarged. But it is the cylinder side port only that should be enlarged, not the duct and exit port at the flange. I think an exit port with a 20mm diameter is quite sufficient for a 40cc engine. This should be of course converted to an oval port with the same area. I haven't calculated it yet so I'm not sure whether the stock outlet is already larger than this but I'm pretty sure that the exhaust duct could benefit from actually filling the bottom side.
This theory is simple wrong, you shouldn't make a smaller exhaust to get less step, you should setup your cylinder in the right position to the piston. At bdc the top of the piston should be in one line with the bottom of the exhaust port, there should be no step.Here is the theory. It's pretty simple to understand. With a higher exhaust duct floor, there is less step between the piston edge and exhaust duct, which should improve exhaust blowdown flow.
View attachment 158241
There is also other benefit which comes from less exhaust duct volume. A tuned pipe can pull fresh charge into the exhaust duct and back to the cylinder more efficiently when the volume is smaller. That helps the pipe to create larger pressure fluctuations.
I bet that no one has done a documented comparison about the exhaust duct and exit port enlargement, without including any other modifications in the comparison. So I don't regard it as a proven modification. I of course want to try this and see for myself, if I manage to do it I will post the results.
Not sure how you will prove it. Face to face hesd to head build would really be the only way. What dimensions are you looking at or do you even know the principals of a TOOL BASED engine in general?Yes the right side cylinder is ported too much.
The header modification is ok, that's how the oval shape should be converted to round, or then using an adapter piece. The only problem is that the header is too large to begin with.
Challenge accepted to prove it wrong