probably shitty connection or a bare wire barely touching something enough to make it flicker from motor vibrations or something. sounds like its time to pull out the ole multimeter and start testing
21cc dome is just a pump gas dome... you wont notice that much of a gain at all. like everyone else has already said, get a nasty port job done then some velcro cause you will need to strap your ass to the seat
theres this oval track where i live that the sprinters and modified cars race on that is open sundays to quads... a bunch of my friends go, hoping to have mine back up and running soon so i can try it out.
that swing arm is similar to the first one i bought on ebay... long story short shitty welds and waste of money, lasted about 2-3 months then got scrapped. your better off getting a chromoly one that wont let you down