Expansion Chamber

squirrel said:

I got the SBP expansion chamber kit but it only came with one of the blue silicon tubes...the big one that mates the bent tube to the chamber. the other two were black rubber which deteriorated.
squirrel

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Thanks - Just to be clear all our pipe kits and replacement hoses are now expensive black 4 ply silicone. Pretty tough stuff. If your exhaust even comes close to melting it, you are running way too lean and hot. The seal pieces were never rubber, they are pure silicone and did fine as seals. The problem is that they tear easily with any little gouge, because they have no layers and no fiber reinforcement. The 1" is for the main connection and 7/8" for the seals. The seals are not structural.

I have only done 4 or 5 SBP Xchamber builds but never have liked the hose stuff.

Sorry Paul, I know the reason is so we can route and tune the pipe and copper is easy to cut, but I just haven't ever been able to make the old blue and new black stuff work or look good.

I have heard of two things that are supposed to work.

1. You can do a hybrid solder/braze with a propane torch on the copper/steel joints if you use Silver solder.

2. JB weld in and outside the seams. I figure a nice JB weld blanket around all the copper on to the real pipes might be great.

Again, I haven't tried either, but plan to so I'll share.

The REAL trick with any Xchamber is how to route it and where to anchor it.
The SBP's are big pipes that can't just rely on the cylinder mount alone.

I bring that up because I have a local customers bike here that he started an extreme build on, and ran into way more mechanical problems than he expected for his second build so he brought it to me.

He had 3 boxes of all top quality parts and got a really good start, but his bike is full suspension and he put a NuVinci hub in. That is not important though, the point is the back end is full suspension so from the BB back there is no place for a back pipe mount that didn't move.

Long story short he bought a one-piece Xchamber too but it literally stuck out like a sore thumb that the pedals hit by 1.5", and final output right up against the BB.

I took the SBP perfectly port matched first piece and the one piece other Xchamber up to my great little welding shop around the corner, had them hack off the crappy fixed small flange on that one piece pipe, and weld the SBP part on it so it aligned exactly where I wanted it.





A little high temp silver motor paint on the $20 fitting/welding and the sacrifice of the SBP flange it works for this build.

Paul, can anyone buy just your perfect port matched initial mount piece?
Can I at least buy another one so the rest of this new pipe can be used (please)?

I will attest to this, I have used a few of each type of pipe, and though SBP's is bigger and requires more work to mount and tune, they sure kick ass performance wise over the one piece cheap ones... IF you do it right.
if you are a rookie looking for just 'a little more', the one piece pipes are your speed, but if you have the skills and want the most, you can't beat SBP's pipe performance and adjustable tuning.

It's fine if you improve on it yourself. I've got no problem with that. But the silicone hose works fine - no they don't last forever but they last a good long time. Remember the small pieces are for sealing - they are NOT structural. They don't hold anything together. They simply seal the seams after you have your pipe in place very securely.

Anyway - I sure wish we could sell the header, but we never have any spare and we can't even keep up with regular production. We'll try to get some made separately but in almost 3 years we have none left over!

The SBP expansion chamber is a must have. Initial assembly is relatively simple, other than stretching the supplied heat resistant rubber tubing over the pipe connections. The supplied rubber lasted me about 6-7 months, and I've since replaced it with fiberglass muffler repair tape & header wrap which when done right works great. I've wrapped the first foot or so of my pipe around 5 times using different methods, all failed. My mechanic gave me the secret which is the fiberglass muffler repair tape, but first wrap the pipe seams with approx 3 layers of household tin foil, neatly folded NOT scrunched around the pipe, then the fiberglass tape which seals by itself once you run the engine, then the header wrap of your choice. Use a small radiator hose clamp at both ends to secure the header wrap & you are good to go, also leave a small opening in the wrap where the spring tensioner attaches to the pipe or else it will get too hot & pop the spring.....and the longer the pipe between where it exits the cylinder head & the point where it bends around, the more torque you will get. I didn't cut mine at all & can practically take off from a quick push & I'm 190. Good luck!

Pablo said:

Anyway - I sure wish we could sell the header, but we never have any spare and we can't even keep up with regular production.

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Those are good problems to have, there is no such thing as selling too much Paul ;-}

derekian72 said:

My mechanic gave me the secret which is the fiberglass muffler repair tape...

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Thanks for the tip ;-}
Most people run direct drive and the low end, especially on 48cc motors, are what benefit from that long straight piece for the low end torque.

I run nothing but SBP shifter bikes myself.
With them and good gears I don't need low end torque, the gears do that for me, where I need the power is around 3/4 throttle to push me once air resistance is a bike factor (35 MPH and above) so I cut mine in half, which leaves about 1/4" after it is coupled.

Heck, I spend more with SBP than on the motor kit!
Standard items for most builds is air cleaner, Xchamber, HP plug wire and Iridium plug, dual pull brake lever and front mount.

This is kinda funny. I have a beach cruiser, I weigh 300 lbs, no expansion pipe, no shift kit, and I got 35 mph out of my 48cc engine before it broke down. To the guy who asked about castor oil, I wouldn't recommend it in these little engines. I could be wrong, but as far as I know it is racing oil, and you don't want to use racing oil in these little engines.

I bought a chrome c-shaped expansion chamber when i bought my kit. I need to bend it because the end lays right up against my pedal cog. Also the middle where the chamber is the thickest, the weld sticks out too far and I cant turn my wheel otherwise it would hit the chamber and probably break it off. Do these c-shaped chambers bend easily in a vise? I'll upgrade to the sbp chamber asap. But for now, I'd like to use this, at least to the better gas mileage.

What you should do, if you have the skill and tools is step 1) get a block of hard wood like oak and drill holes in it to match the spacing on the flange for your c exhaust. Step 2) carefully think about HOW you want to bend it. Step 3) bolt your exhaust to the block and hold the block in a vice. Step 4) get out the propane torch and carefully heat it until it is reddish orange, then bend gently in the direction you want to go. Any metal from that seam you can grind down with a grinder gently as needed. You may have to install and uninstall and re-bend the exhaust a few times, but this should do it! Peace
-LS

Thx. I do in fact have a propane torch in my garage. I'll do that tonight.

No problem! In exchange for the advice do you think you could do one thing? Take pics and post them somewhere, I'm a pic fanatic

Sure. Ill post pics here. I'll do that tonight.