What expansion Pipe?

Also today, i noticed that the cylinder head was different from my spare motor, One of the cylinder heads Had more of the curve where the pistons meets the spark plug, could switching it make a difference or not, really curious
 
You'd have to put photos of each up, compression increase is likely to make your biggest difference with regard to heads.
 
I personally think the torque I I is a good idea these kits need all the bottom end available I mean they don't have enough to star from a stand still outta the box plus I live in sf which has the steepest hills this is just opinion though I had a raw motor on a springer fork shcwinn in Virginia and 44 th was more then enough torque easily hit 35 but regardless what do you senior members think of thishttp://www.kingsmotorbikes.com/Motocross-Poo-Poo-Pipe-Muffler.html I know kings is not SBP but it seems interesting.
 
cashark said:
I personally think the torque I I is a good idea these kits need all the bottom end available I mean they don't have enough to star from a stand still outta the box plus I live in sf which has the steepest hills this is just opinion though I had a raw motor on a springer fork shcwinn in Virginia and 44 th was more then enough torque easily hit 35 but regardless what do you senior members think of thishttp://www.kingsmotorbikes.com/Motocross-Poo-Poo-Pipe-Muffler.html I know kings is not SBP but it seems interesting.
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I honestly see nothing that the poo poo pipe offers over a stock pipe, actually I think a stock pipe with a couple simple mods will probably out perform the poo poo pipe because the longer the pipe is the more restrictive it is, and overly restrictive pipes kill these little engines in my experience, hill climbing power is gonna suffer big time with a pipe that doesn't allow the engine to breathe well, I have a gutted out stock kit pipe on one of my bikes just for experimental purposed for a short time, it has NO catalytic junk in it and I cut the little stinger tube off and just drilled out where it was to enlarge the hole, that alone made a huge difference in hill climbing power and my top speed is good on that bike, it has 24" wheels and I run a 30T rear sprocket on the 24" wheel so my speed on top is 40+ mph and it still pulls the 24" wheel good for my area, in a very hilly area like SF I'd be running a 36T on the 24" wheel probably and a 41T or 44T on a 26" wheel probably.

Either a well set up expansion pipe or a free flowing stock kit ppe set up wins out in my opinion over the poo poo pipe.

One more very important thing is that the exhaust pipe flange should be as closely port matched to the cylinder as possible and the gasket needs to be trimmed if need be so that there is not extra restriction as the exhaust leaves the engine

Map
.wee.
 
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Build a pipe that looks like this......with similar dimensions.....and hang on!





I'm sure that's no help to you, but that pipe on that 46cc 2-stroke is amazing.
 
Holy $H!T,
also would a pocket bike exhaust be better than a stock. Not for performance, just better breathing.
 
I was using a pocketbike expansion chamber on mine originally and it did make a big improvement over the stock pipe, especially in the lower rpm range... I noticed right away that it accelerated a lot better, top speed was still about the same but it got there a lot quicker and smoother.
I'm running a modified KTM 50 pipe now and it's even smoother, but it's also on a new engine that has a lot more power...
 
Here it is... with the pocketbike pipe... I basically hacked up the stock pipe and part of the pocketbike header so I could get the bends in the right places and welded up the header, then slip fit the expansion chamber over the header. It leaked a little at the slip joint but still made good power.

8nq0.jpg
 
Mine is off a 2013 KTM 50SX and I had to cut it in 4 different places to re clock the bends then weld it back together... As you can see, I'm not completely done because I don't like the way the stinger is pointing but it's rideable and both quieter and faster than the pocketbike setup, even without a muffler installed.
I need to find a tight radius bend section of 1" tubing that I can replace that stinger with so it can direct the exhaust towards the rear and then I'll add a silencer, but I like it for now.
here's the exact one I got off ebay... used dirtbike pipes are cheap and most of them have thick enough metal to make welding them fairly easy, you can also braze them with a mapp torch if you don't feel comfortable welding thin metal using nickel/silver brazing rod.

http://www.ebay.com/itm/111176119578?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT
 
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Over here its $80 for a new ktm 50sx pipe and thats with the muffler, which is actually cheaper than any other pipes made for the engine. Ill try get one after i get over some issues on my engine..
 
mapbike said:
lowaus, here is a pic of the pipe I am running on one of my bikes, I cut about 4"/10cm off of inlet pipe and I'm using flex pipe of about 30cm/12" from engine exhaust flange to the expansion pipe.

This pipe is doing a better job than any of the others I have tried so far, other set ups did good for low and mid power but were lacking on the top end, but this set up is giving me good power all the way around and I did not loose top end speed, this bike currently moves me down the road at 69+kph/43+mph

It has some port work, a ramped piston and a well tuned carb, the lower assembly has preety nice balance also, no harsh vibes at any RPM from start to wide open, that make a big difference also.

$_57.JPG

$_57.JPG


MaP
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yep this one for sure. fun and usable.
 
sub66 said:
yep this one for sure. fun and usable.
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Yep this is the best of the small pocket bike pipes I've seen, got one on my heavy 26" cruiser and with my 215lbs on it I cruise right along at 43-44mph with a 34 or 36T on the rear wheel.

Good pipe with a short larger dia. header pipe leading into it.

Map
 
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