i got a question me and my friend are making a gas scooter the moter is hooked up and its a 47cc cag we have a giovonni dirt bike exhaust thats hooked up and we need to cut the cans off and i wanted to know if that would affect anything and can u bore out one of those exhausts thanks.
I finally got around to doing the Stock Pipe Mod and I must say I am impressed. I am sure a lot has to due with luck that I found the ideal sizes to use the first try. First I made alignment marks on the belly and the header. I cut the weld at the cone where the header connects and removed the excess from inside the cone. Then I cut 1 1/2 Inches off of the header and Mig welded the header back in in alignment with the marks I made. I then cut the widest part of the belly open as straight as I could and added 2 inches of 2.75 exhaust pipe. That is how wide my stock belly is. I also cut the weld where the muffler extension comes out of the cone and made sure there was no excess in the cone. I then welded the extension back onto the cone.
I started the bike and noticed the sound difference right away. It sounds a lot crisper and it has a snappier throttle. Thats with stock jetting and air box. I have a rocket key, reeds, and clutch springs. When I took it for a ride I noticed the bottom end increase right away! It also has a wider powerband. Top end increase is 2 mph easily verified with my GPS.
I ran it against my buddies modified CAG and he has a fatboy pipe, velocity stack, and his is jetted. He has the same mods as me. I beat him off the line easy, and kept pulling on him. So a very noticeable increase in power and top speed with the sizes that I used. I have not pulled the plug yet as it runs so good! I may still need to open the airbox up and go up a size on my jet for maximum power and performance. But so far so good! Thank you whoever first tried the mod and realized its gains and sharing to the community!
I then cut the widest part of the belly open as straight as I could and added 2 inches of 2.75 exhaust pipe. That is how wide my stock belly is.
I got the piece of belly from my old tailpipe from my 2004 Silverado. A part of the tailpipe fits perfect, I cant describe which part but all you have to do is cut the belly in half and measure, then start hunting down a piece of pipe to fit. Could always use sheet metal, tack it up and weld the seem.
ok ive kinda skimmed through the posts, im runnning a hot 47cc cag with high compression spark plug ( vw plug lmao had to rethread too lean burned the stock on in lol) with a 6 inch boost bottle help me out here, my pipes got a PHAT hole in it and i wanna CCR the sucker ( chop cut rebuild) i need some direction as far as how to construct it. my low to lowmid range is KILLER! but my mid to mid high is weak but she tops off beautifully and runs solid bearings out at the top guys.
Just read through this thread, bradmack87, and you'll learn how to do it. All it takes is a little patience and a lot of reading - skimming through the posts isn't going to help.
Let's see some pics of your bike, and a list of the mods you've done to it. A VW spark plug??
I put together this graphic showing modification of the stock cag pipe. The mod consists of three cuts and welds, removing part of the header and adding belly. The resulting pipe looks much better, how does everyone think it woud perform?
itll gain horse power but youll lose acceleration bad for turns and turns r where u want it the most.
Thanks,
You guys gave me alot to to think about cause I have to Mod.
two pipes, I want all out TOP END, for my Drag Bike, with two
Big Bore 49cc HP, w/ full circle cranks!! I am turning the head
pipe, 180%, an running the exhaust under the Bike!! Some of
the Head Pipe must go, about 4 to 5" total off the Chamber &
I might come out the back of both to One Big Pipe, 2"!! EPR!
Stock pipe mod night and day difference! 
