Expansion chambers & performance pipes for China 2 strokes

[brett7777]

A while back, over in the boardtracker threads, I came across a comment that suggested that changing pipes on China 2 strokes didnt make much difference.
I knew that couldnt be correct, as all my experience with 2 strokes in the past suggested that if you have a correctly tuned pipe then you can coax much more power outta them.
I changed to the simple 'performance' pipe on this page. It made an amazing difference.
Note that he has developed a more involved design on there too. He claims 74 km/h with a 48cc (carbon frame) with that design.
Performance Exhaust Systems Cycle Pro Motors
The pic is a diagram of expansion chamber theory

 

[moonerdizzle]

Thank you. That is very informative

 

[bharmon]

Thank you Brett, that was exactly what i was looking for. Did you fab. an expansion chamber exhaust using this guide?

Bruce Harmon

 

[brett7777]

Thank you Brett, that was exactly what i was looking for. Did you fab. an expansion chamber exhaust using this guide?

Bruce Harmon

No. But the guy who drew it up is getting very good results with China motors.

 

[talbotti]

heres my 66cc bike with slightly ported cylinder, lowerd cylinder head and scooters modified expansion chamber. i might put a 19mm dellorto to it when i get my intake finished. the bike has a poor low end tourge with that pipe but mid and hi end power is great.

ImageShack® - Online Photo and Video Hosting

ImageShack® - Online Photo and Video Hosting

ImageShack® - Online Photo and Video Hosting

sorry the images are bit dark but because i was in my garage.

 

[Venice Motor Bikes]

That pipe looks awesome! All 2-stroke pipes are that way; you can tune them for either low, mid, or high RPM power, but you can't have it all...

Good job on it!!

 

[maniac57]

I welded a junk pocket bike chamber to my china exhaust flange...No way it was tuned right for the engine but it made a very large difference in power! Now it's one of the first mods I do with a new kit> Cheap and easy(if you have a welder)

 

[allen standley]

I used an expansion pipe from a pocket rocket. Tuned properly--probably not.
Immediately noticed better midrange seemed to breathe easier. Looks hotter'n **** and snds like an old McCulloch chainsaw my uncle used in the woods.

 

[Gan Man]

Hi members, I was wondering if SBP expansion chamber is about the same as one on bike berry &canada skyhawk site ? Prices are slightly different ,which is better ?

 

[NunyaBidness]

Hi members, I was wondering if SBP expansion chamber is about the same as one on bike berry &canada skyhawk site ? Prices are slightly different ,which is better ?

I've never used any of them but the guys at SBP are members here and take care of their customers. I've only ever seen people praise them for fast shipping and quality products. I don't think you could do better any where else.