PocketBike Pipe for 48cc works excellent!!!!!!!!!!!

Motorhedz

New Member
Well, the project is finally complete and works excellent!!!! I know a few of you guys have used a couple of different styles of pipes for these 2-strokes so I figured I would give it a shot. Check out the photos. Here are the gorey details for those of you who want to try it out:

1) Stock Pocketbike pipe and silencer. You can find them on Ebay for around $25
2) Cut off headpipe close to the weld spot where the bend begins.
3) Cut off the mount bracket and save it.
4) You will have to make your rear mount bracket first so you have a way to hold the pipe roughly in place to make the measurements for the headpipe.
5) You will have to remove a section of the headpipe to shorten it enough to make the proper new bend fit correctly. ( did that make sense??)
6) Have someone help hold the pieces in place or tack them together with a weld spot here and there. Or you can mark them so you know exactly how they will fit together when the pipe is off the engine.
7) You may have to open the mount bracket holes a bit to fit the exhaust cyclinder studs.
8) Use a wire-feed mig welder and weld the pipe pieces together after you have marked how they fit together (or tacked them).
9) Grind the welds down and paint the pipe with Fast Black Gloss.

Simple as that. Now for the good stuff:

1) Intake tube was match ported to the cyclinder. I widened the area that connects to the intake port because the intake tube is round and the intake port is rectangular. This is very bad. I ground the **** out of it to get it to match as best as possible, obviously I couldn't make a rectangle shape out of a round tube but I was able to really oval the tube to match much better than the narrow stock sized opening.

2) Match ported the exhaust port to the exhaust mount bracket. They were way off, too.

3) Reshaped the exhaust gasket to actually allow the exhaust to flow properly out of the port. I had to trim almost 2mm all the way around the inner diameter of the gasket.

4) These engines have serious air leaks where the carb is mounted to the intake tube, where the intake tube mounts to the cylinder, and where the cylinder head meets the cylinder ( due to lame closed-nuts that restrict proper tightening ), just add a small loc-washer under each nut and re-torque.
Use a good quality gasket sealer and add to the intake tube on both ends to eliminate the air leaks. This helps with erratic idling and lean running conditions.

5) Replaced lame spark plug cap and plug with an NGK cap and an NGK plug.

6) I run the chain direct, sprocket to sprocket. This is unorthodox, I know, but anything that interferes with rolling of the chain causes friction which, in turn, robs power from the wheel. However trivial this might seem, it's makes a big difference with a tiny motor like this.

7) Stock main jet with the slide needle dropped to the leanest setting ( top notch on the needle). Excellent throttle reponse throughout.

8) ATV thumb throttle instead of twist.

All this gives me a top speed of 40-45, with a 44t rear sprocket, depending on ambient air temp here in Upstate NY. Humidity makes it run slower of course. It climbs hills much better and I use it commute 30 miles to work every nice day I get. I weigh 185lbs and it pulls me with little effort compared to the stock set-up. I bet this thing would hit 50MPH with a 36t.

Don't forget to check out the photos. Hope this inspires somebody.
 

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shiloh0

New Member
Jun 28, 2008
88
0
0
i need a mig welder. i noticed those flow restrictions also, my intake actually had a piece of flashing inside that blocked at least 1/3 of the flow. good job on that pipe!
 

FileStyle

New Member
May 27, 2008
724
1
0
Decatur,IL
pipe looks like a leg burner to me! have you thought about putting a heat shield around it? I ride with hookworm1 and he recently dropped his ride and it give him a 3rd degree burn on his L. leg right above the knee! ouch! safety first!!!!!!
 

jasonh

New Member
Jun 23, 2008
1,590
0
0
37
Longmont, CO
My dad has one of those, I've used it a few times to weld up a cat and muffler and stuff...works fairly well. Gets the job done if you only need it for light-duty stuff.

I'm considering getting an oxy-acetelene setup one of these days. Not sure if I'd want that or a mig first.
 

Motorhedz

New Member
I thought about that way, too, and wish it would have worked better. I know from experience ( I own a small retail business, selling parts for ATV's, Snowmobiles and Motorcycles as well as doing engine mods ) that a long headpipe is not the way to get the most power out of your pipe. If you notice, any pipe on a 2-stroke machine that produces good power, does not have a long headpipe. You probably already know this but some of the other readers might not.
Just a quick bit of trivia....If a 2-stroke engine has a long headpipe, it will still run, but no-where near it's potential. A short headpipe allows the expansion chamber to to send the proper backpressure or "sound-wave" to the cylinder much more quickly and at the correct "frequency" to produce maximum power. That is why they are called "Tuned" pipes. They operate on sound frequency....that's also why they sound soooooo sweet!!!!
 

Jemma Hawtrey

New Member
Dec 29, 2007
288
2
0
Essex, UK
I thought about that way, too, and wish it would have worked better. I know from experience ( I own a small retail business, selling parts for ATV's, Snowmobiles and Motorcycles as well as doing engine mods ) that a long headpipe is not the way to get the most power out of your pipe. If you notice, any pipe on a 2-stroke machine that produces good power, does not have a long headpipe. You probably already know this but some of the other readers might not.
Just a quick bit of trivia....If a 2-stroke engine has a long headpipe, it will still run, but no-where near it's potential. A short headpipe allows the expansion chamber to to send the proper backpressure or "sound-wave" to the cylinder much more quickly and at the correct "frequency" to produce maximum power. That is why they are called "Tuned" pipes. They operate on sound frequency....that's also why they sound soooooo sweet!!!!
Which is why the pipe I just had fitted gives me lots of power all the way through the rev-band (like about double) but nothing more on top end *sigh*

I must admit it sounds like a happy bumblebee now - not a wasp with PMS

Jemma xx
 

Andyinchville1

Manufacturer/Dealer
Dec 26, 2007
502
1
18
Scottsville, VA
Hi Jemma,

With all that all that new power from your tuned pipe you could take advantage of it by gearing up (smaller rear sprocket or for friction drives a larger "roller")....

If you do that just be careful with your new found speed! ;-)

Andrew
 

oldtimer54

Member
May 15, 2010
539
1
18
On a bike
I have one and its not to bad if ya pack it with fiberglass. I wraped mine as well and not only dont I get burned but the pipe is much quieter.
 

flybytaco

Metal Molding Madman
Oct 17, 2009
1,176
1
0
seekonk MASS
i run a 6 inch header max 1 inch dia i'm getting serious power increases too the rest of the pipe makes a huge diffrence too. I have my desighn down pat.