SBP Pipe, q's

Humsuckler

Humsuckler

New Member
im interested in buying the SBP pipe Sick Bike Parts
im just wondering what kind of powerband it puts out from stock to "tuned" i have read that you can adjust it aording to the header length.... anyone got some pics of one of these mouted on a cruiser frame?
 
I am not faulting sick bike parts at all but i have a few questions as well.

I had purchased a tuned pipe from sbp and installed it on my raw 50cc. The power increase was comparable to having no muffler at all which was a decent increase in power. A buddy of mine bought one as well and installed it on an 80cc and the power increase was INSANE. In the instructions it said that the pipe would work for both 50 and 80cc kits but the deference in power increase was incomparable.

Anyway, I noticed that my top speed actually went down after installing the pipe. I can assume that this was because the pipe was tuned for a lower rpm, my question is... what power band is the unmodified pipe made to improve? and is it different for an 80cc compared to a 50cc?
 
Try shortening the header length for a 49cc. About 12" is right for a 80cc. The 49 has a little quicker stroke.
 
The 49cc engines tend to want to rev a little higher so shortening the header length on a 49cc will improve the rpm advantage the 49cc has to offer. But trying to compare a 49cc engine to a 69cc engine doesn't make a lot of sense, I mean the 69cc is 30% bigger.

I would try taking an inch off the pipe to start and keep shortening a half inch at a time after that.
 
There is no factory length only a start point, and for most the start point is too long and in general will improve the horse power best over the 2 to 4 thousand rpm range. Again this is dependent on your engine but is a good start point. By progressively shortening the pipe you can tune it to where it works best for your engine and gearing.
 
Remember how the pipe works. The exhaust sound wave expands down the front taper then hits the rear taper (which is usually at double the angle of the front) reflecting the wave back at the header tube. The idea is to get the header length "tuned" to have the wave hit the exhaust port just before the piston closes it. Stuffing some of the energy back into the port along with some of the exhaust gases as the piston goes up. The faster the engine is spinning (or the shorter the piston stroke is) the shorter the header needs to be to deliver the charge at the right time. To long a header and it's late, to short and it's early. A little long and you get a broader band. As they get shorter the rpm range is more sensitive but the pipe adds more to the HP. It's a balancing act.
 
Last edited:
I recently ran the stock pipe for the initial brake in period of 300 milies, today i took the pipe off and removed the tip, i cut the inner tuber off and drilled two quarter inch holes on each side of the nut that holds the tip on. The amount of take off power went from decent to an insane amount of torque, as well as less throttle at crusin speed of 27 mph with a 36 tooth sprcket. I wouldn't consider an after market pipe when the simple mod to the stock is well worth the time!!!

this is a 66cc raw motor, .wee.
 
I just installed the SBP expansion pipe assembly on my bike :D

I'm not a huge fan of it's mounting, fit, various plumbing bits, or aesthetics and I need rework it a bit to find it's "sweet spot" but I can tell ya this - it does have a pronounced effect in low end pull on my 66cc.

I'm quite pleased with that ;)

I don't think it made my bike any louder but it's hard for me to tell as it also moved the exhaust outlet from underneath me to behind me. It changed it's tone though, now it sounds like a tiny lil pissed off dirtbike lol

When my next kit arrives (so I have a spare exhaust) I'm going to cut the stock pipe to see if I can't use it's head pipe for the expansion chamber. I think it'll fit and this should reduce the number of plumbing bits, silicone tubing, and help conform to my bike's shape a bit better.
 
I just remounted my SBP tuned pipe, only supposed to be a test fit - it's worked so well I'm going to leave it :D

SBP2.jpg


Yep, that's just two stainless hose clamps and two chunks of high pressure/high temp hose o_O Yet it's so solid and exactly where I want it, I think the only thing I'm gonna add is bits of inner tube between the clamps and the frame.

SBP.jpg


Heheh, yessir - more high temp hose makes a fine extension! Stops the exhaust from spewing nastiness on my kickstand and bag and actually helps take the "bang" out of the sound and deadens it a bit.

I don't think it looks that bad even with hose clamps all over the place... mebbe I'm just gettin' used to it lol
levers2.jpg
 
Last edited:
hi,

i was wondering if i made mine longer would it lose power.?

i am just fitting one put it comes to high on the cross bar and when i come to fit the tap is resting on the pipe plus the tank is way to close to the tank, so in order to clear the tank and fit it to the frame i need to lengthen it by about 18" it will be running on 69.7cc Starfire GenI GT4 with a jackshaft the bike is a gt lts..
 
As was mentioned earlier in this post the header length is critical to the correct tuning of the pipe. 12 inch total distance from your exhaust port to the start of the expansion chamber is a good starting point. Adding 18 inches would completely ruin the tune of the pipe and eliminate any advantage in horse power the pipe offers. Here is a link to my GT frame build. http://motorbicycling.com/showthread.php?p=314778
It required the addition of another 45 degree fitting to get around the down tube. The header length on this bike is around 13 inches and is a little long for optimum performance but since it is a dirt bike I was more interested in torque than high rpm performance so it works well being a little long.
 
My pipe is at 10 inches. With the mods that I have, it's a good balance between low-end torque and high-end power band.
 
You must log in or register to reply here.
Back
Top