Kymco ZX50

[zombie]

110-120 is just fine. Can u post a photo of the pipe? You shouldn't be guessing at these mods. .05mm is alot to be off by. and that can be done in an instant. If at some point u can put a piece of paper inside the jug, and trace the edges of all the openings by rubbing w/ a crayon or such maybe we can get down to the exact set up on paper for your kit. The tracing has to stay steady as these will be measured to the 1'000TH to figure what it needs. I posted a 250cc when it is a 125cc. It seems the detonation is the only BIG issue left for you. the pipe may have something to do w/ it along w/ the port timings. Have faith Brother. You're too close.

[sidthesloth]

Yeah mate I saw that 125, and yes it does look rather similar to mine, what part of the exhaust do you want to see? inlet pipe or output side? With tracing the inside of the cylinder I wouldn't know what it should be, as you said it is very accurate measurements. From reading Gordon Jennings book all that maths is way over my head. I can still do the trace if you want it, though probably not until Tuesday as I go to work early tomorrow.

[zombie]

Any time. Once you get it traced do you have access to a dial caliper set? You will set the piston to bottom dead center, cut the paper to fit to the top of the jug, hold it in place w/ some tape, and trace away. I really want to get a ball park where the ports fall in relation to the piston at BDC. Just a general pict of the pipe, or the link to it. I wanted to see if it an expansion pipe or baffled. It should match the jug as it was sold as such but u never know. It may be forcing burning mix back into the jug. Just another thought.

[sidthesloth]

Weeell, I sorta jumped the gun a little, I traced the ports and put it all back together, I took a measurement from ports to top of cylinder but not from piston. I will attach a pic of the paper. When I put it back together I used both gaskets, I bolted the barrel down aqnd the piston is a little shy of the top but not by much, I couldn't get anything with the feeler gauges. The detonation is gone, but performance is a little down. I took a couple of pics of the barrel and will have a look, I think it might be the same as the one Josh is working with.

[sidthesloth]

Right, here is the pic of the barrel marking.

[sidthesloth]

Pic of the exhaust, I expect the expansion chamber would be part of the canister??

[zombie]

You are the best sid. This will help alot. The port map! Is the piston sitting at the bottom of the paper, or did you remove the jug to trace it?

[sidthesloth]

Jug was sitting on the table, the measurement was as best I could get, couldnt find a ruler to fit and I didnt know you wanted the bdc measure. I will get it tomorrow.

[zombie]

On the pipe can you see any tack welds indicating there are baffles inside the pipe? I think another issue is the sound wave that would normally empty the cylinder is bouncing off the back of the pipe, and forcing hot/burning gases back into the jug. A few 3/8" holes drilled into the end may relieve that but I would like a second opinion. I'm gonna invite Josh to take a look at this thread, and get his input if he will be kind enough to share some of his thinned out time w/ it.

[sidthesloth]

Thanks, that would be very much appreciated. I have asked customx22 for a pic of his pipe, I think it may be the same as mine, and he may be able to shed some light on it.

[zombie]

It will depend on the jug more than anything else. The pipe may work GREAT on one jug, and not at all on another. You have HUGE ports in your jug. Just for comparison you could try to reinstall your stock pipe w/ all else being the same, and see what happens. Ie detonation, torque ect.

[sidthesloth]

I think that was the problem when I first put that kit on, holding back the gas and over heating. the original pipe is for a much smaller engine.

[sidthesloth]

The ex. port is 34mm, the trans. ports are 13 and 20mm, the boost? port is 22mm across.

[zombie]

Agreed the stock pipe would not allow the gases out fast enough. Maybe the new pipe is pushing it back in...? You are there tho!

[sidthesloth]

Allright, I have done another port trace with some measurements this time.
The measurements above are the distance from the top of the piston,
On the inlet port I have got 3 measures because of the wave in the cast.
The measures inside are the width of the port. Hope this helps.