SBP Expansion Chamber... AWESOME!

Brent436

Brent436

New Member
I just recently got my SBP expansion chamber in. I have a 48cc Grubee Skyhawk. Before i was running the stock Black Cat muffler (held my motor back a ton aparently). The difference is amazing. I used to hit around 25mph(ish). Now Im hitting 35mph! I have a shift kit so that helps too, but this expansion chamber is amazing! It really pulled a lot more power out of my motor. I recommend this upgrade to anyone who wants to pull more power out of these motors and doesnt mind a bit more noise (sounds like a dirt bike, sort of).

I know this upgrade is kind of obvious and unoriginal, but Im just really pleased with it so I figured I would share haha.

-Brent
 
I have one also..unfortunately my engine kit is still en-route, but I did spend a couple hours last night and this AM hand filing the expansion chamber kit manifold clean and smooth. Hoping I will have the same Happy results.
Cheers
 
Living at 5000 ft elevation I'm still fiddling with my carb adjustments to unleash the full potential of my SBP pipe. I finally broke down and bought a CNS carb this week hoping that I can dial it in better than the stock carb. Does anyone know if the Dellorto jets that SBP sells are compatible with the CNS carb ?
 
On the topic of SBP exhaust, I will say that it is the easiest way to get torque to pull up hills. If you like to fiddle, adjustable header length moves the power up or down in the rev range. The motor itself is limited by its port timing to rev higher, but the pipe sure brought a smile to my face after the first ride with it! I just finished breaking in my stock 66 with a SBP standard shift kit, then added the pipe and smiled like a fool all day riding around. The stock motor wouldnt pull the last gear, even on down hills! now I cruise in top gear, only down shifting for steep (for florida) hills. A SBP shift kit with a pipe is the ultimate mod combo.
 
There's after-mufflers available, SBP sells 'em too - but I kinda went a different way, but it's really easy & cheap too :D

BarelyAWake said:
IMG_1010resized.jpg


"I needed the headpipe for a different project" and that's the result ;)

It's a modified SBP expansion chamber, ported stock pipe & extended glasspack silencer. While the spring retention system on the SBP manifold is great and reduces metal fatigue - I couldn't bear to have the blue hi-temp silicone on my vintage ride... it just kinda clashed and Ima slave to fashion I guess. The extended glasspack quiets the exhaust to roughly equivalent to stock (sounds different/better - but no louder) and other than being 6" or so longer has little/no effect on backpressure as it's a clear passage straight through.

It's a pretty easy mod (glasspack) as it's simply 2" aluminum conduit, a chunk of metal window screen, a lil fiberglass insulation stolen from my wall & a coupla pop rivets, the stock head pipe slid right in to the expansion chamber with a lil chunk of the SBP system as an adapter :D (yus, I still need to trim & paint the one lil exhaust clamp) o.o

I liked how the curvature of the stock pipe pretty much matched the bike heh *shrug*
Click to expand...

Was supposed to be about cats, ended up rantin' bout full exhaust systems & suchlike: http://motorbicycling.com/f13/catalytic-converter-mufflers-15857.html

More glasspack babble: http://motorbicycling.com/f3/whats-difference-20708.html#post197273
 
I got My engine installed, I took the time to clean up the exhaust manifold and enlarge it a bit to match the exhaust port... and the half day riding I got before shoddy Chinese quality control kicked in told Me that this is plenty of power for a bicycle once I get her running again and the carb dialed in I'm going to probably pass on the performance carb and MM head. Its Plenty fast for a bicycle to go.
Cheers
 
Looks like I may be trying one sooner than I thought.
The one piece cranks on the Moon Dog are too narrow to fit by the stock pipe, so it's either a Hug Low pipe, Poo Poo, or an Expansion Chamber pipe.

Or, I suppose a jackshaft would do the trick.
The cranks in them are plenty wide, and then he could use those 7 gears ;-}
 
chainmaker said:
I got My engine installed, I took the time to clean up the exhaust manifold and enlarge it a bit to match the exhaust port... and the half day riding I got before shoddy Chinese quality control kicked in told Me that this is plenty of power for a bicycle once I get her running again and the carb dialed in I'm going to probably pass on the performance carb and MM head. Its Plenty fast for a bicycle to go.
Cheers
Click to expand...

Yeah. I wonder how long that attitude will last...

You so many funny!

From drn2 to xct2 and .wee.
 
I could use some more top end speed.
But I get to play with an X-chamber, on it's way from SickBikes today for the green Moon Dog.

The kid poo pooed the Poo Poo Pipe options ;-}

I will it down it to low end torque, he needs it there even with a 66 and the last thing I want is to see that old bike going 35+ or whatever it is suppose to do.
 
DudeZXT said:
Yeah. I wonder how long that attitude will last...

You so many funny!

From drn2 to xct2 and .wee.
Click to expand...

You learned so complete speaking the chinglish. All the world useful so many china product instructions everywhere quality. Soon everyone knows and will buys already many.
 
Xchamber mounted on the Moon Dog with a 66cc Grubee.

moondogLeft.jpg


moondogRight.jpg


All I can say is wicked scary torque and fast.
Brand new and she fired up on the second pedal and darn near left me sitting on the street behind it.
Even the shifter bikes I build were nothing like this.
It didn't just start, it was like firing a rocket with direct drive.

I love the sound too, DB wise not louder than a stock pipe, but it does sound different... Kind of like a dirt bike racer, and it performs like one too.

I had some issues with the kit but I informed Jim and SBP about them and as usual they are addressing the little things.

If you want to scare yourself with a performance boost for ~$80, this is the way.
Just hold on, I wasn't exaggerating about the rocket launch feeling, and it sure took me by surprise.

The full story about this build here KC's Kruisers - Motorized Bike Forum - Josh`s Moon Dog
 
FreeWheeler said:
You learned so complete speaking the chinglish. All the world useful so many china product instructions everywhere quality. Soon everyone knows and will buys already many.
Click to expand...

Happy Time go fast motors buys I two. Fast plenty go! Already two many buys I.laff
 
Last edited:
There exist exhaust choices for modification, we like you buy options that delete volume of wallet you. Smile we decision you make, markup good deal(us for), therefor, parts you throw at unknowingly, increase horsenoise 'cept buy more muffler, work good last longtime.
 
Mac said:
There exist exhaust choices for modification, we like you buy options that delete volume of wallet you. Smile we decision you make, markup good deal(us for), therefor, parts you throw at unknowingly, increase horsenoise 'cept buy more muffler, work good last longtime.
Click to expand...

Wow. You must have used Google Translate to come up with all that. ;)
 
KCvale said:
Xchamber mounted on the Moon Dog with a 66cc Grubee.

moondogLeft.jpg


moondogRight.jpg


All I can say is wicked scary torque and fast.
Brand new and she fired up on the second pedal and darn near left me sitting on the street behind it.
Even the shifter bikes I build were nothing like this.
It didn't just start, it was like firing a rocket with direct drive.

I love the sound too, DB wise not louder than a stock pipe, but it does sound different... Kind of like a dirt bike racer, and it performs like one too.

I had some issues with the kit but I informed Jim and SBP about them and as usual they are addressing the little things.

If you want to scare yourself with a performance boost for ~$80, this is the way.
Just hold on, I wasn't exaggerating about the rocket launch feeling, and it sure took me by surprise.

The full story about this build here KC's Kruisers - Motorized Bike Forum - Josh`s Moon Dog
Click to expand...
one question. im new to this stuff. i know about motors but not these kind. but the question is what is the transation for BP. is that the pipe?
 
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