Expansion chamber for 2 stroke - WHAT DO U RECOMMEND???

brett7777 · Nov 3, 2011

I would like to find an expansion chamber exhaust for my 48cc, preferably something that would fit ok with the boardtracker look, please tell me what you have tried & how it went, price, where you got it...?

chainmaker · Nov 3, 2011

Sick Bike Parts, Ive tried it with a 66cc and was very happy.

F_Rod81 · Nov 3, 2011

It all depends on what type of power-band your looking for. I have the SBP pipe myself, it is great. It can be tuned for low-end or top-end, I have a 10" header on my SBP ex. chamber and it is balanced for both low-end torque and top-end power. If your going for a BTR look then go for the Grubee banana pipe. It is a little louder then others, but it will complete the look and when tuned right it is a good little pipe. Just browse through the intake/exhaust thread and you'll get all the answers you need. Take some pictures for us when you get the pipe you choose.

Grubee pipe = $40 + s/h Click here
SBP chamber = $70 + s/h Click here

brett7777 · Nov 3, 2011

............Thanks!

Alson333 · Jun 24, 2012

The SBP expansion chamber is. What my friends got he lost the back part at the verry end, and is woundering if he needed it, I dont dealy know, jts lowder now, but be likes it lowd, anybody know

bairdco · Jun 24, 2012

the part that fell off is a silencer. all it does is muffle the noise. it'll run fine without it, just louder.

putting any kind of muffler on an expansion chamber has (supposedly) no effect on the power at all, as long as it's not restricting it. the hole in the pipe is basically a bleed valve for the exhaust. it's kinda complicated. you can google expansion chamber and learn all about it if you want.

Alson333 · Jun 25, 2012

Thanks for letting me know, he'll be happy to know, his engines all right r.ly.

crmachineman · Jun 27, 2012

Hi.
These guys are basically right. The expansion chamber that Sick Bike Parts and Pirate Cycles sells seems to be proportioned well, although I suspect the lead in pipe will be smaller than ideal for maximum power. I have personally tried the less expensive expansion chambers you will find on Ebay, or from Gasbike.net; they work O.K., but just O.K. The proportions of those is not ideal, but it's simpler to make. I just finished making a custom expansion chamber. I purchased a used chamber on Ebay and cut it up in several pieces. Then I welded it up, so it fit the bike. When it comes to the exhaust of these engines, which depend highly on exhaust for scavenging, bigger is better. In some of the pictures, you can see some of my handiwork, which is O.K. Notice the gradual taper leading into the engine. This kind of work was done with very primitive tools. like a hack saw, hand grinder, a TIG or MIG welder and some scrap tubing.

brnot

-Fred

DaveC · Jun 28, 2012

crmachineman said:
Hi.
These guys are basically right. The expansion chamber that Sick Bike Parts and Pirate Cycles sells seems to be proportioned well, although I suspect the lead in pipe will be smaller than ideal for maximum power. I have personally tried the less expensive expansion chambers you will find on Ebay, or from Gasbike.net; they work O.K., but just O.K. The proportions of those is not ideal, but it's simpler to make. I just finished making a custom expansion chamber. I purchased a used chamber on Ebay and cut it up in several pieces. Then I welded it up, so it fit the bike. When it comes to the exhaust of these engines, which depend highly on exhaust for scavenging, bigger is better. In some of the pictures, you can see some of my handiwork, which is O.K. Notice the gradual taper leading into the engine. This kind of work was done with very primitive tools. like a hack saw, hand grinder, a TIG or MIG welder and some scrap tubing.

-Fred

First that cylinderhead of yours is the cat's a$$ and anyone with half a brain should get one and I had a Puch head on my bike

.

The cheaper pipe is basically untuned. There needs to be a head pipe for tuning purposes. When I raced karts they also had a movable stinger section. Extended for long tracks and short for short tracks. I don't know how well it would work on a bike but maybe someday I'll experiment with it

ivan H · Jul 3, 2012

Yeah, I've seen cart chambers where the convergent cone is mounted in the pipe in front of a spring. As gas flow increases they r forced backwards, thus spreading the power band over a much wider range, with different tension springs being available to enable tuning of the pipe. Cheers

ivan H · Jul 3, 2012

yeah, I've seen cart xpansion chambers where the convergent cone is mounted in the pipe in front of a spring. As gas flow increases the cone is forced backwards, thus spreading the power band over a much wider rev range. Different tension springs allow tuning of the pipes range. Cheers

ivan H · Jul 3, 2012

sorry bout the double posting guys, I had a phone malfuction & didnt think it had uploaded. Anyway its there twice now, just 2 b sure 2 b sure, cheers

crmachineman · Jul 3, 2012

Damn! That is interesting! I've heard a lot of good tips coming from people involved with go kart racing. Seems like that crowd has a nice bunch of tricks up their sleeves!

zpt

-Fred

Alson333 · Jul 3, 2012

My buddy lost his silencer off of SBP expansion chamber, any way ae ordered the muffler they sell for there chamber and jt fits on the tube 5/8 perfect, he tightened it up with the hose clamp, no problem, its alittle quiter esrs dont ring now, like before pino.

ivan H · Jul 3, 2012

So the muffler would quieten a stock SBP chamber down a lot?? I know they aint excessively loud, but I would like 2 quieten some 2 avoid drawing attention. Maybe I can make 1 up packed with stainless steel wool. Crmachineman, I have formulars somewhere 4 x chamber sizing, header ID, max cone ID etc, I'll c if I can dig them out 4 u. I know that header ID is important, 2 big & it pulls 2 much mixture thru, 2 small & it dont pull enough. Stinger ID is important 2, more than length. 2 small & u can "hole" the top of the piston. Cheers

Alson333 · Jul 3, 2012

The muffle for SBP chamber puts bass to the noise, when I got it for 7 some bucks I could blow in it an hardly any resistence. See before without the silencer it pinged real load, like metal to metal ping ping anyway it hurt tbe ears, now its go bass to it, no hurting the ears, but not making desl quite, my friends happy with it, a cop told him before, I heard you, I didnt see ya pino.

Alson333 · Jul 4, 2012

Excuse my spelling, when I get in a hurry, I miss some ,etters. Anyway its not a bad little muffler, it looka like a lawn morer muffler, in the pitcher at sick bike parts it was brass colar, when I got it it was silver with a brass reducer on the end

ivan H · Jul 4, 2012

Thanks 4 that tip Alson333, thats exactly wot I'd like 2 quieten it 4. Street riding isnt quite allowed here, & I've already had 1 expensive episode with the local LEO's, cost me as much as the entire bike almost, so drawing attention is something I definitely wanna avoid. Cheers

ivan H · Jul 4, 2012

Hi Crmachineman, I found a few formulae 4 u, might b more than 1 post on phone. Micheall Forrest's formular for size of header at the port is: 2x square root of (( 0.00085x displacement in cc x max rpm)/3.14). I'll post Bell's formulae for maximum diffuser cross sectional area in another post as I'm running outta phone screen & posting blind is like,,,, posting in brail. Cheers

ivan H · Jul 4, 2012

Maximum diffuser cross sectional area is: single stage diffuser is 6.2 times the beginning of header area, dual stage is 9 times beginning of header. Area = 3.142 x radius squared. He gives diffuse angles from centerline for 2 stage diffuser for 50 - 80cc of 3 degrees & 5 degrees, stating that a longer first cone & shorter cone benefits mid range torque. Nother post, phew. Cheers

Expansion chamber for 2 stroke - WHAT DO U RECOMMEND???

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