General Thoughts - Expansion Chambers

Those pipes arn't going to give you any better performance than your stock pipe. I wouldn't worry about spending any money on an expansion chamber. Only reason I put one on my last bike was I had one lying around from an old pocketbike project.
I think people get way to carried away trying to add performance parts to these bikes. After all they are motoized bicycles not motorcycles.
As far as your pedal hitting your muffler, just put a bit more clearance in the holes on the flange that is bolted to the block. That will give you a little more adjustment.

John

About your pedel hitting thr muffler. I lossened my muffler pushed in away from the muffler holding it, then tightened it up putting preasure on it, and it cleared. If that dont work open the holes on the muffler flange, like said before. I had the same clearence like you have, with the peddle, so I had to put my expansion chamber upside down. I had to put heat wrap around my expansion chamber, so it wont bern my leg. Other wise my putlng upside down was easy

In my oppinion there is no reason to get a expantion chamber unless you know you can get away with the noise were you live....Im happy with my stock pipe and its nice and quit and keeps the cops from bothering me....

Now on the other hand if these bikes had lots of power and this is what it took to make them come alive and squeel the tires I would go for it,but we are dealing with bikes that just dont have much power but lots of fun....
John

Something for you guys to ponder. I was involved in APBA during the '60s-70s. I crewed for an outboard legend, Ron Anderson. He raced Alky burning 15cid (A hydro) and 20" (B hydros) and was the first person to run 100mph with a 15". The engine was an Anzani twin and Ron was the first to use expansion chambers. You can imagine how difficult starting an allout engine from the low speed leaving the beach, to running 100mph down the straights. I can tell you that it's difficult. Ron decided what he needed was one lenght to get off the beach and up on plane, and another for top end. His first effort was two expansion chambers with a valve to switch them. It worked, but four expansion chambers was a lot of stuff hanging off the back of the boat. He then went to a sliding setup (trombone)and using a lever in the cockpit would shorten the lenght after getting on a plane. It worked very well and resulted in a World record surpassing those of 3 classes above him. He also built a dual expansion chamber 125cc bike with the diverter vlave that was a terror on a little dirt track somewhere northeast of Seattle.
The bottom post in this link mentions the "trombone" expansion chamber
Ron Anderson - Boat Racing Facts Forums

There is a lot of potential in the expansion chamber. They can be tuned for different RPM ranges as well. The ones you are buying are generic, built more often for fitment and style than for maximum effectiveness. However they can be "tuned" for a particular RPM range that you feel you can use the most help in. For those with hills in their riding, longer will be better. For those in the flat, play with shortening it. As Ron Anderson showed the outboard world 40 years ago, you can even have one do both, or two with a valve to switch between them if you had room for dual exhaust. Have fun

i grew up riding two stroke dirtbikes and 4-wheelers, so when i bought my china girl kit i knew that an expansion chamber pipe would be necessary. I went with the kit from SBP, after installing it (i've only ridden it once with the pipe on) i noticed an immediate increase in throttle response with a much wider powerband in the mid range rpm's. Now it sounds like a dirtbike instead of a weedeater. just my two cents.
squirrel

ADDICTED BICYCLES said:

Ok guys, I think I'm torn. Lol. The Expansion chamber seems good and all, but to be honest, the bike I have my engine on right now, barely fits the engine in terms of pedal clearance. My pedal hits the muffler, and the pedal arm has very slowly been grinding into the muffler. There isn't anything I can do here to fix that, for I have next to no tools, and I've never done any kind of fabrication or welding on one of these kits.

That being said, for me to get an expansion chamber, that means a huge string of mishaps. In my history with these engines, I need something that will install simply, and not be a pain in my ... Anyways, here is some exhausts I've found. Do any of these add any kind of power or performance like the expansion chamber? Is one better than the other?

Thanks for your posts guys, I know I ask a lot of questions, but I want to put my money in the right place this time. I'm tired of buying junk.

Here's the pics. Thanks again!

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from what iv'e read on the forums before those could actually make you lose power, butit would seem quieter to you since it would put the exhaust, and therefore the nose behind you.

as for your pedals hitting, look into getting a wide arm crank set. they sell em for $20-$30. if you have the right type of crank and basic knowledge of bicycles you can easily install it yourself.

bluenosegoat said:

The kit comes with everything you'll need including a nice quality gasket. I purchased the extra silencer (I think it was 5 bucks, figured I'm paying for shipping get it all). I never ran it without the extra silencer but if you look at the pic of it in my previous post you'll see the included "muffler" and the extra silencer behind it. Side by side with my other bikes I would not say its any louder at all. I actually think its a little quieter. Definately sounds better and now my bike has zero four stroking and good power through all throttle posistions. Mounting is fairly easy. On my bike the clearance's are very tight for the pipe between missing the pedal crank and tire. I think sometimes it touches my tire but at that point down stream it is not very hot. I have almost 200 miles with the pipe now and wish I had them for all my bikes! If you have any questions at all Pablo and Jim at Sick Bike Parts are fantastic! They have the best customer service I have dealt with. Super fast to respond and more than willing to help you. Very good guys! You get what you pay for most of the time and with sbp you get that and a lot more. Hmm I sound like a comercial! Anyway I'm sure you'll love it. I know i do.
I havent tried any of the other pipes out there but after having the shift kit and knowing the quality these guys put out figured I couldnt go wrong. I am going to experiment with a pit bike pipe as I'll be welding in extensions for a cruiser I built so I dont want to mess up a more expensive pipe. I am so hooked on these bikes!

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those guys make great products, timely shipping, comprehensive paperwork and even include a little sticker. very professional. but their attitude does change a bit when you tell them you're not a shift-kit rider...patience shortens.

Russell said:

This may not go by the 12" max rule but the power increase shocked me. I built it to go with the flow of the frame.

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I notice you didn't mention that's a Motovelo chamber. I'll tell you what Fellas- those motovelo guys are doing some pretty cool s**t. I'm building a stretch mustang, and with SBP pipe in hand, I have just discovered the straighter, smooth flowing lines and high polish of the santa barbara crew's expansion chamber. It looks like the perfect pipe for a stretch. just sayin...