I cleaned up the ports before I put the Taida head on the 61mm engine. I also changed the carb mounting - I removed the black plastic spacer plate. This helped the accelerator pump clear the engine mount. My only concern is the temp of the carburetor. I think that plastic spacer was acting as an insulator. I put my palm on the carb earlier and it felt much warmer than I remember it feeling in the past. I'm still on the stock exhaust.
Anyway, the buggy seems to make plenty of power down low and is very responsive to throttle changes. I seem to have gotten my top speed back, too. I'm right at 35mph on the same straight I've been testing on.
I'm really excited about redoing my exhaust. I'm half-way through the header creation process and have a cheap can en route. I measured the recesses that were cut in the Taida head and ordered carbon steel tubing that fits exactly in the inner groove. Basically the ID of the tube matches the port width and the OD of the tube matches the OD of the first step that is cut into the head. Should seal up nicely and have no step changes in passage diameter all the way out to the silencer.
Honestly I'm not sure if it would be beneficial to step down and increase the exhaust gas velocity (this would increase the vacuum experienced at the valves at TDC) or if it would be better to not step change at all as I plan to do. Anyway, I picked one and went with it. Hopefully next weekend I'll have the header/pipe complete and mounted. OD of my pipe is 1.125" with around 1" ID.
This pipe will fit inside the other pipe I was using. Apparently the last DIY header was 1.125" ID.
