What expansion Pipe?

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lowaus

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Aug 24, 2013
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australia

Theon

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Jan 20, 2014
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Steve at OZbicycl... is a *^%#wit! and the banana pipes are crap.
The Z box pipe looks only slightly better and I wouldn't waste your money.
It might make your bike sound a little better (louder) but I seriously doubt it's going to have $160 worth of performance improvement.
You may get a slight improvement from less restriction, which is easy enough to do by mod'ing your standard pipe.
I have not tried either of these pipes, because I wouldn't waste my money on them.
And I certainly wont spend another cent at OZbicycle...
If you want an expansion chamber that actually works without spending a fortune you may have to make it your self.
 

lowaus

New Member
Aug 24, 2013
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australia
Steve at OZbicycl... is a *^%#wit! and the banana pipes are crap.
The Z box pipe looks only slightly better and I wouldn't waste your money.
It might make your bike sound a little better (louder) but I seriously doubt it's going to have $160 worth of performance improvement.
You may get a slight improvement from less restriction, which is easy enough to do by mod'ing your standard pipe.
I have not tried either of these pipes, because I wouldn't waste my money on them.
And I certainly wont spend another cent at OZbicycle...
If you want an expansion chamber that actually works without spending a fortune you may have to make it your self.
Thanks for the help Theon.
How could i get make my stock pipe better. Ive heard stories of people modifying their stock pipe and adding a carb get speeds of up to 50 KMPH. Also what exhaust are you running .:-||
 

Theon

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Jan 20, 2014
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I have tried a pocket bike pipe similar to that, was nothing special.
I have 4 bikes 2 with home made expansion chambers, the better pipe was made from scraps of bicycle frame and a piece of 3" exhaust that I cut vee's from to get the angles I wanted, it gives a nice powerband.
The motor I'm building at the moment is getting a KTM50 pipe that I have cut rotated and re welded, havn't tried the pipe yet but have high hopes for it.
My least modified engine is in a 24" BMX with a 36t sprocket and easily pulls 60+ Km/hr will wheelstand from low revs with a bit of clutch slip and runs a standard pipe (but one of the better ones with a heat shield) and has only been well match ported and a dozen or so 3 or 4mm holes drilled through the exit tube on the inside of the pipe. It is not to loud and is ample for a mildly modified engine.
Match porting the pipe to the jug made a very noticeable difference, and I would be spending your money on a decent burr, which from memory I used in my battery drill.
For a look at my other pipes have a look through here, http://motorbicycling.com/showthread.php?t=53563&page=12
 

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mapbike

Well-Known Member
Mar 14, 2010
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Central Area of Texas
I have a "Cat Eye" pocketbike expansion chamber on one of my fastest cruising bikes, it pulls good and I can cruise at 43 mph = 69+kph

I did cut about 5" of th hader pipe off and the header pipe from engine flange to expansion pipe is 1 1/8" ID and about 13" long, no mods to the silencer on this pipe, I think it may be a bit restrictive since the exit tube is less than 1/2" ID but it does a good job and I wont know for sure if the exit is a bit to reztrictive until I try a slightlylarger pipe in the future.

This pipe cost about $40 here in U.S., ill post a pic here as soon as I can get on my home computer I stead of this "smart" phone.

Map
 

lowaus

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Aug 24, 2013
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Thanks for the inputs fellas.
My all stock 66cc is pretty bad. It has trouble reaching 39KPH(24MPH).
How could i ever make it faster.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
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Match porting is when you use the gasket to scribe the ports and open all ports up to full gasket size.
The idea is no steps or restrictions on airflow in port transitions to manifold or pipe.
Most people open the gasket to the larger side of the assembly and then port the small side to match, hence the terms
"Match porting" or "Gasket matching"
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Match porting is when you use the gasket to scribe the ports and open all ports up to full gasket size.
The idea is no steps or restrictions on airflow in port transitions to manifold or pipe.
Most people open the gasket to the larger side of the assembly and then port the small side to match, hence the terms
"Match porting" or "Gasket matching"
Excellent explanation maniac....

No way this could have been said better......

Map
.wee.
 

lowaus

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Aug 24, 2013
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So i did get rid of the lips on my ports, but then when i was putting the jug back on, something bad really happened, the top piston ring snapped, because the jug wouldn't go back on. Am i really screwed or can this be replaced.
 

Davezilla

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Mar 15, 2014
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Rings are cheap and easy to replace, what I think happened is that there are pins in the ring grooves to keep the rings lined up and from rotating in the groove... real bad for 2 strokes because the ring end would end up in a port and break off and usually destroying the engine in the process.
All ya need to do is order up some new rings, they cost $5 to $7 depending on who you buy from, reinstall the new ring or rings, make sure that the gap is lined up with the pin in the ring land and it should go right on. Also make sure the ring isn't installed upside down, you'll know because there's a cutout for the pin on each ring end.
 

lowaus

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Aug 24, 2013
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australia
Thanks Davezilla, how do i install the rings on without snapping them, i took out my other ring which wasn't broken, and bam it snapped while coming off, I've ordered 2 and their on their way.
 

Theon

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Jan 20, 2014
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I use a timing wheel for any porting/port timing as the barrels can be different to one another, so I do not measure in mm, but degrees.
All my motors are 40mm stroke also, so that can change measurements a little if your is 38mm stroke.
I widen the exhaust considerably as well as centering the port.
I widen the inlet a little,
But correct port timing is the key.
For good all-round performance ex. 150 Deg Dur, Tr. 120 Deg Dur, and inlet 120 Deg Dur.
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
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.




MaP
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
That's more like it.
Don't know if they're availiable in OZ though,
Would likely have to get it from the states.
here is a link to a place in California that has them for $39 U.S.

http://www.ebay.com/itm/191030738358?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I paid $10 for mine on ebay new, but that guy has no more of them, wish I could have bought about 3-4 from him before he sold out, but I got last one.

I have this one coming in the mail now, gonna give it a try also, its a bit larger pipe than the cat eye pipe, I think it is the same pipe that Arrow is using on their race bikes, so it must breathe good.



its a $60 pipe so I hope it will do a good job also.

Map
 
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