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Discussion Starter · #1 ·
Just wanting to reassure myself. Seeing as I have little knowledge of how different stages of modification changes preformance. I figure someone else will know better.

Just got done putting the motor together, getting it running, and then taking it for a spin.

Before: Me and my brother have the same bike. Mine was faster than his pretty much at all speeds, but not significant until the later RPMs, as mine will hit a higher top speed. Both bikes are very close though, and hit the pipe at the same rpm, or very closely.

Then I did the following...
-Tapered carb, it was 14mm stock interestingly enough.
-.3 reed. Dremeled out that middle support in the reed cage.
-tapered needle (3rd position) and adjustable jet
-cone filter
-here's the big stuff. Ported out head and indexed piston to 124 degrees of intake and 180 degrees of exhaust duration. I figure this is conservative enough to allow slight adjustment if needed. Also widened exhaust port a small amount, maybe .5mm if that.
-Still using stock exhuast

Now: Bike definately has a lumpier idle. Seems to run alright, has a strange roughness at a spot in low/mid throttle. I don't know if this is a fueling issue, or if it is just the timing overlapping badly. Below and above that it seems fine. Motor is definately louder and might be a little hotter, didn't really check temp before. I suspect the increases exhaust flow is to blame.

Now if we race from a stand still. His has some more low end, not a lot more, but some. We are within a few fet up until he hits the pipe and I can see him jump forward, maybe 5 feet ahead of me. But by then I am speeding up, doesn't ever feel like I hit the pipe hard like I used to, if I'm even hitting it at all. Just slowly rev up higher and higher until I pass by. Top end seems higher to me, but that's the butt-dyno for ya.


Does this seem about right for a ported head without a tuned pipe?

And any suggestions on dimensions? I plan on cutting up the stock chamber and rewelding it together. Probably shortening header and lengthening belly.
 

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anytime you do the porting you will lose the lowend, but if it is ported,( and ported right) you should have a very strong powerband. if you are not getting the powerband, could be the pipe. i have two pipes that i made, one has good low and mid, and one has good mid and top. both pipes are completely different on the track so the pipe could be a problem if dont think it is fast enough. i would stay away from the stock pipe all together unless you plan on completely replacing the header porteion of it, expand it right off the head and maybe making the chamber a little longer and or fatter. it is just kind of a trial and error thing.
 

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Discussion Starter · #3 ·
Yeah, that's it exactly.. I'm just not really hitting the power band at all.

I'm not surprised or anything, I didn't expect much with the stock pipe on it anyway. but I'm looking to get more mid and top end power, right now it feels almost stock but with less mid range and no oomph. Low end is somewhat useless on these tiny motors anyway. You just can't get around the fact that they can't produce much torque. The only real power to be made is through revs.

Mind if I ask what you have set up on your bike? I'm trying to look around for good examples...
 

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Pmantix84 my engine is responding something like yours. Did you ever get it on the pipe (rrrr's) again?

I needed a little more bottom end so I raised the exhaust port about 1 mm and widened in about 1mm. Blended the exhaust port to the pipe (stock) and removed the head gasket.

It seemed to pick up the bottom but never got that screaming top (had to trade something) with the stumble at partial throttle.

Looks like my exhaust duration is 177 and my intake is 130 (pie plate degree eyeball wheel).

I'm thinking the stumble my be fuel/air related (never was good at reading used plugs) but the bike started first pull no choke idles high then loads up. (too rich?) This may pick up rrr's also.

Thinking about indexing the piston. There is a ton of material blocking the transfer port.

What angle did you use? 45 deg?, 60 off vert?, 60 off horiz?

Thanks in advance
 

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http://wwws.sun.com/software/download/#java

Try going there and downloading java. Its should install smoothly and after a reboot you should be able to launch the program. You can also download the program to your computer if you choose to.


This section is from the tune pipe site:
To make life for Windows users even easier, you can also download the Windows Installer file which contains all you need and installs JavaPipe correctly. In fact this is probably the best way for Windows users.

http://www.mh-aerotools.de/airfoils/java/javapipeinstaller.msi
 

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You drilled out the center bar and now you're letting in a lot more fuel into the engine, which is good, but too much fuel with hinder performance. Since you have the 0.3mm reeds, try getting the 0.5 reeds from adrenaline, put that underneath the 0.3 mm reeds, and see how the bike runs with that. You didn't do much porting of the head and indexing of the piston to affect performance a great deal.

You're losing low and mid range grunt by porting. You'll need to upgrade your pipe in order to get back that low and mid. In my opinion, the stock pipe sucks.

PMantix84 said:
Just wanting to reassure myself. Seeing as I have little knowledge of how different stages of modification changes preformance. I figure someone else will know better.

Just got done putting the motor together, getting it running, and then taking it for a spin.

Before: Me and my brother have the same bike. Mine was faster than his pretty much at all speeds, but not significant until the later RPMs, as mine will hit a higher top speed. Both bikes are very close though, and hit the pipe at the same rpm, or very closely.

Then I did the following...
-Tapered carb, it was 14mm stock interestingly enough.
-.3 reed. Dremeled out that middle support in the reed cage.
-tapered needle (3rd position) and adjustable jet
-cone filter
-here's the big stuff. Ported out head and indexed piston to 124 degrees of intake and 180 degrees of exhaust duration. I figure this is conservative enough to allow slight adjustment if needed. Also widened exhaust port a small amount, maybe .5mm if that.
-Still using stock exhuast

Now: Bike definately has a lumpier idle. Seems to run alright, has a strange roughness at a spot in low/mid throttle. I don't know if this is a fueling issue, or if it is just the timing overlapping badly. Below and above that it seems fine. Motor is definately louder and might be a little hotter, didn't really check temp before. I suspect the increases exhaust flow is to blame.

Now if we race from a stand still. His has some more low end, not a lot more, but some. We are within a few fet up until he hits the pipe and I can see him jump forward, maybe 5 feet ahead of me. But by then I am speeding up, doesn't ever feel like I hit the pipe hard like I used to, if I'm even hitting it at all. Just slowly rev up higher and higher until I pass by. Top end seems higher to me, but that's the butt-dyno for ya.


Does this seem about right for a ported head without a tuned pipe?

And any suggestions on dimensions? I plan on cutting up the stock chamber and rewelding it together. Probably shortening header and lengthening belly.
 

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Does anyone know what the stock exhaust port area is? I also was wondering if you port the exhaust would you take the area at the cylinder or at the junction of the pipe assuming you tapered the port out from the inside of the cylinder.

Anyone?
 

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Discussion Starter · #10 ·
Yeah, I have the .5 reeds as well.. I'll try sticking them in there and see how she runs.

Haven't done the pipe yet. I wanted to have it welded up by a pro, but everyone around here is asking like 50 bucks for 3 freakin' welds. I'm looking around for something else now..

Anyone know of a good upgrade pipe that won't cost me over a hundred? I really don't want to spend that much for a pipe on such a small cheap bike. I built my whole exhaust from my turbo back on my nissan for 65 bucks, and that's a lot more pipe and a lot more welding.

Thanks for the help guys
 
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