Kymco ZX50

[sidthesloth]

I changed the plug, went for a ride no real change, gave in to temptation and changed the jet, though it is not as snappy it is all round better so I will leave it for a day or so. When it died off it would pick up with throttle and quite snappily so, in answer to your question I think too lean, maybe 130 is a little small. with the 132 in now I reckon it might be worth regaining the extra response by gearing but this is all new to me. I will try to put up a pic of the plug that came out.

[Shaka]

I think you are about right with the jet, but your getting some detonation at full throttle.  I think you need to either put in a 2nd base or head gasket to lower the compression.  You my need to play with the jetting again after adjust the jug.  I would go for the 2nd head gasket if your happy with the port timing.  If you put in a second base gasket keep in mind you will be raising the ports slightly.  It may be best to pull the head and see what your port exposure is towards the bottom of the stroke.  I think either gasket will solve your detonation problem, but one will give performance than the other!  Also have you checked your compression recently?  That plug is kinda a funny color, I've never seen mine that color.  Are you running any other fuel additives?  Those will make some funny colors sometimes.

[sidthesloth]

Well, I dont know anything about port timing but I am sure you will enlighten me in time. no fuel additives, maybe a little hot? will have a look at plug tomorrow. I wik gowith the base gasket as I can cut it myself and not wait a week for it in the post

[zombie]

Sounded too lean. Try the 130, and lower the needle. Give it a run at full throttle w a new plug. then you can start tuning down the range from there. My idea is once you get the wot dialed in it is a matter of finding the needle position. I think the color is from either the brand of oil or a detonation front right under the plug. raising the jug will stop that. Just to be sure tho I saw a cool tip on scoot invasionusein a thread of solder wicked in thru the spark plug hole. The idea is to get the solder to the edge of the cylinder, and rotate the engine to squish the solder. That will show how much clearance there is between the piston. and the head. (squish band) use a very thin piece as shaka and I both think you may not have enough clearance there. It should be between .5-1.0mm (.8mm being best). this last bit will take a lot of guess work out.

[zombie]

My bad. Do the solder bit before moving the jug.

[sidthesloth]

That  sounds like  a good idea, will try that tonight. With the 130 jet the needle was at the lowest setting. is at the lowest setting now with the132.

[sidthesloth]

Tried the "squish test" with a piece of solder 1.21mm thick, no squash, tried to get all areas of cylinder but no "squish so must be plenty of clearance.

[sidthesloth]

The oil I am using is Fuchs Silkolene Scoot 2.

[Calothrix]

I'd get some strange looks if I'd ask for that oil in the US.

[sidthesloth]

  yeah, I did too, until I found out the correct pronunciation.

[Shaka]

That's odd you couldn't get any squish measurement!  I don't understand what that noise you're hearing is if it's not detonation?  Are you sure you were getting the solder all the way to the edge of the piston?  From looking at the pics of your plugs, I don't think you are running lean enough to cause it with greater than 1.2mm of squish.  I've been wrong before though!  Hey, maybe I'll learn something new when you figure it out!

[sidthesloth]

Yeah, Im satisfied i got it to the edge, and tried in a few places around the cylinder. the noise is not loud but gets louder as engine gets warmer. the noise is not there under load but when backing off and just slight deceleration.

[Shaka]

When I had it it was only at WOT when the rpm's got to a certain point.  I think yours sounds like it is in the top of the mid-range.  I would think raising the needle would fix it.  You might want to do a plug chop at 3/4 throttle, or whatever throttle postion it makes that noise in, and see if it's lean.  See if you can replicate that noise for long enough to hold it there and see what the plug looks like.  You may end up having to go with a differently tapered needle.  One where it's fatter at the top and skinnier at the base, with a shorter taper length.

[axy]

I'd get some strange looks if I'd ask for that oil in the US.

Btw. "(der) Fuchs" is a fox in German.

[sidthesloth]

Righto, been at it again, 135 jet just for the sake of trying, not real good. The night before last going to work on a fairly good downhill run at around 80 kmh with the 130 jet started surging until I backed
off but coming home in the morning along a different route (long slight uphill) held 80 quite well.
Last night going to work with the 132 jet down the same downhill run surge was still there but not nearly as much. Today I tried the 135 jet and bogging too much at wide open, lower top speed (struggle to make 80), so tried a 48 pilot jet (original was 45) but no real improvement. I have now gone back to the 130 main with the 48 pilot to see how that goes. Unfortunately I don't know where to get any needles from. What I forgot to mention was I put the needle up 1 notch to the second lowest before any jet changes today. Tomorrow I will get some more plugs and do some chops if I get a chance, w.o.t., 1/2 and 3/4 throttle and see what that shows. My lack of experience is showing and am trying some experimenting with the jets, (must be frustrating for you blokes on the other side of the world).