Expansion chamber

[KCvale]

After testing it didn't seem to make that much if any difference other than the exhaust was less restricted compared to most other exhaust types..

Lets all review what an expansion chamber actually does...

The way 2-cycle motors work is to try and do the exhaust and intake in the same up/down/up cycle of the motor so it can fire on each top visit, and because of that a lot of unburned (green) fuel goes out the tailpipe.
An Expansion Chamber (on the right of that animation), named for its peculiar looking fat section, is tuned to push that un-burned fuel back into the cylinder, thus giving each cycle an extra Boost of fuel.

You tune the pipe by the length of the header pipe.
If that pipe is tuned right you are set.
If you are not sure, get a SickBikeParts X-chamber.
http://sickbikeparts.com/expansion-chamber-black-exhaust-pipe/

It is tuned with the short straight copper tube.
It is already tuned for a 48cc, for a 66cc cut the copper tube in half, in essence just butting the 2 copper angle pieces together.

 

[Frankenstein]

some of them will do 7 grand but you really don't want to go past 6 with stock bearings

So then I wonder if that pipe (while being different from the one in that image posted, but might be the same thing according to street) is even applicable in this instance... I guess the world will never know, until a couple days from now when he plans on installing it on his bike.

 

[Frankenstein]

Lets all review what an expansion chamber actually does...

The way 2-cycle motors work is to try and do the exhaust and intake in the same up/down/up cycle of the motor so it can fire on each top visit, and because of that a lot of unburned (green) fuel goes out the tailpipe.
An Expansion Chamber (on the right of that animation), named for its peculiar looking fat section, is tuned to push that un-burned fuel back into the cylinder, thus giving each cycle an extra Boost of fuel.

You tune the pipe by the length of the header pipe.
If that pipe is tuned right you are set.
If you are not sure, get a SickBikeParts X-chamber.
http://sickbikeparts.com/expansion-chamber-black-exhaust-pipe/

It is tuned with the short straight copper tube.
It is already tuned for a 48cc, for a 66cc cut the copper tube in half, in essence just butting the 2 copper angle pieces together.

Do you not see what my post was about... I said in a roundabout way that the only noticeable change in power was that it was less restrictive on the bulldog than with something like stock. The effect was almost like pulling the muffler off completely but not as extreme. Probably since a bulldog is a good 1 inch pipe compared to stock 3/4. There wasn't a noticeable band of power increase on the engine with it installed except possibly at the very lowest rpm range where it felt like it pulled a bit stronger on a "just above idle" glide. It also seems like it's typical to see that from these expansion chambers that aren't actually tuned for these motors but marketed as such...

The bulldog just sounded better really, maybe it was the metal they used and it resonated nicely or something, or I'm going deaf and it's just louder than normal so I notice that too.

As to Carlos, look at kcs info on what a expansion chamber actually does, and realize it's got a lot of science behind it, most of it is careful measuring, and so unless you build a pipe tuned to your bike the most you are hoping for is to get lucky.

I would be interested in a thread covering a range of pipes that are considered aftermarket that people have tried, and the experience they had using it.

 

[Street Ryderz]

some of them will do 7 grand but you really don't want to go past 6 with stock bearings

A stock engine can turn 8-9 grand all day with no issue!At 11,000 the older style small end bearing starts to show signs of abuse!The newer style bearing currently being used are good up to 16 grand and are the same style used in 15-20 hp race engines for scooters!

 

[Frankenstein]

A stock engine can turn 8-9 grand all day with no issue!At 11,000 the older style small end bearing starts to show signs of abuse!The newer style bearing currently being used are good up to 16 grand and are the same style used in 15-20 hp race engines for scooters!

He doesn't just mean the small bearing, that bearing in the bigger end of the arm actually gets spun, unlike the wrist pin, and there is the main bearings being what they are, and seeing how wonderful the crank balance is you might implode something if you take it that high, the motor will probably be trying to self destruct at all costs.

 

[Street Ryderz]

He doesn't just mean the small bearing, that bearing in the bigger end of the arm actually gets spun, unlike the wrist pin, and there is the main bearings being what they are, and seeing how wonderful the crank balance is you might implode something if you take it that high, the motor will probably be trying to self destruct at all costs.

I currently have a customers bike in my shop that is box stock but a 2016 build date on motor (grubee skyhawk) the only thing he changed is the exhaust pipe he uses a banana pipe that IMO is a POS and dosent have any gain what so ever!This bike goes 47 mph on 44t stock gear and 26"wheels, I know this for a fact because I rode it with my gps and had someone pace it! it has the new style roller bearings on the rod and stock crank bearings none of them show any signs of wear or abuse!thats 11,000 rpm he rode at for months the balance on these has improved greatly!His repair needed was the plating in cylinder wore through and caused the top ring to catch on exposed aluminum and it shifted and broke!

 

[Frankenstein]

I currently have a customers bike in my shop that is box stock but a 2016 build date on motor (grubee skyhawk) the only thing he changed is the exhaust pipe he uses a banana pipe that IMO is a POS and dosent have any gain what so ever!This bike goes 47 mph on 44t stock gear and 26"wheels, I know this for a fact because I rode it with my gps and had someone pace it! it has the new style roller bearings on the rod and stock crank bearings none of them show any signs of wear or abuse!thats 11,000 rpm he rode at for months the balance on these has improved greatly!His repair needed was the plating in cylinder wore through and caused the top ring to catch on exposed aluminum and it shifted and broke!

I really need to pick up a grubee and make a special build with it, I still have a few speed demons left inside me that need a good exorcism..

 

[Carlos motors]

Bad news guys, I just came from exhaust servis and exhaust can't be installed cause if i put it looking down i cant pedall and if i put it looking up my legs would be burned so..

 

[Frankenstein]

Bad news guys, I just came from exhaust servis and exhaust can't be installed cause if i put it looking down i cant pedall and if i put it looking up my legs would be burned so..

So bend it

 

[Frankenstein]

Or wrap muffler wrap around it, protects you from burns and you can get it in any color you'd like