Trying to tune a 15mm Puch Bing carb (not a clone) on a stock 50cc Sachs 505 D motor with Sachs MLM sidebleed pipe from Treats. I'm starting to think I went too big with the Carb/intake and was hoping someone else went down this road before me. I fabricated an intake riser to match the 15mm manifold in order to raise the carb up to fit on the bike (a very nice and clean 1980 Prima that ran beautifully with stock set up). I got curious after riding stock for a while and wound up jumping down the rabbit hole.
I've tried every jet from 58 to 82 with the needle set on the bottom notch and second to bottom notch and four stroke with every combo. The closest I've gotten on the needles bottom notch is with a 68 jet (low/mid range perfect with nice idle). The closest I've gotten on the second to bottom notch is with 74 jet (low/mid range perfect with nice idle). Still four strokes a bit at 30mph on both settings though. Before I move on to the third notch from the bottom I was hoping someone could tell me if I've got an unusable combination of parts to begin with.
At one point a friend reminded me to check for air leaks in the carb and I noticed that I'd damaged the very top gasket so I carefully cut out the profile of the original gasket from a cereal box and am currently using that to seal the top of the carb. Doing that certainly helped a bit but did not fix the problem. The bike does not four stroke with the air filter off. I've tried both metal and foam bing high flow filters.
I impulsively bought the performance parts and everything actually worked pretty well for a while but it was because the intake riser was leaking air. Probably should have left all of the components stock which I could go back to easily but as long as I've got the performance parts I'd like to use them. My goal was to have this bike hitting 35-37 with the stock cylinder while keeping a large sprocket on the back wheel for super strong low/mid range.