The weirdest thing last evening was that in the quest for more performance I put in my 110 Mikuni jet. Every time in the past that I tried using the 110 jet I would get nothing but too rich four stroking.

Last evening I was rewarded with a clean running engine with a bit more acceleration. The ambient temperature here was still close 90 degrees with high humidity. Does the 120 jet need to be tried? Guess I had better get one.

Jennings speaks to this in his book. He shows this graph of typical behavior of an expansion chamber:
I have been adding 2 inch sections to my pocket bike pipe. I have been using an old standard LP tank for my tubing. I basically have the full length of the tank inserted on my pipe. I figure that if I richen the jetting and get away with it I could be either lowering or raising the resonant frequency of my pipe as I may be increasing or lowering the exhaust temperature.

I would really like to cut the chopped up part of my expansion chamber (It is so ugly) and put in a new piece of pipe but figure that I had better work on the jetting first. Form follows function. Depending on temperature of the exhaust I am around 11000 rpm at peak power. I don't think that 48 mph is 11000.

Much to do!