Originally Posted by Chrisflik
What up to the L.A. heads. Dodgin' cars and dodgin' cops. Am I the only one on one of these contraptions? In almost a year of riding one of these bikes i haven't run into another motorized bicycle bike rider. What up!?! Well... If I'm gonna be the ambassador to motorized bicycling in the Greater Los Angeles area. I promise to be a poor representative. I promise to break all safety and speed laws, ride against traffic and without my helmet. If you ride in the L.A. area and care to cause chaos with other like minded heads feel free to give me a shout. Must be a hooligan by nature though. Have a medical card. And not ride a piece. Peace!!
Chris below is what I did to get biggest HP gain:My chopper / bike is using a Yamaha Y80 # speed engine and is 2cycle based..
The biggest gain you will get if everything else is perfect and RPM is in torque range is a Exhaust Expansion chamber. I was Top at 65 mph This is with 80cc Yamaha 3 speed. I made a dual tube exhaust pipe that the top tube was a dummy and just the end sealed off. I drilled a hole for oil drain into lower tube and use 1/8" steel tube braised to connect. back at entrance of tube I used 2 3/4 elbows to go from top tube into bottom tube and braised everything together. then I installed turn downs on both tubes Lengths bottom with turn down 22" and top 19" and 2" round used exhaust pipe from muffler shop scrap.
the Shop owner studied on how to hide to tubing at entrance and how to fasten to exhaustpipe. we tacke a peice of 4" exhaust pipe to enclose and smooth out then heated it and bent it around the pipe sealing everything and using cutter wheel trimed excess. (we had done the same to seal each entrance tube already)
Once the cover was trimmed and tacked inplace we total braized it to make it look as one. we had fitted hangers to it and once aligned tacked it to exhaust pipe. went back and made a large washer to fit inside lower tube (just a flat circle no holes and braised a 90 degree plate with mounting hole and nut attached and drilled 1/8" hole in bottom tube about 4 " from exit This plate is about 1/16" smaller then the inside of tube.. for sound baffle and helps to raise back pressure.
I am useing original yamaha rims and tires and speedometer so I am close to corrected speeds as the motorbike was within .5 mph of reading on radar gun