Kymco ZX50

[sidthesloth]

Cheers zombie, I will take the GPX to work tonight and work on Sid tomorrow, should I leave the oil system as is and add to the fuel tank as well or just go straight premix? Will put some tape over the cover joint but will need to find something to fill in under the spark plug cap. I didn't check the end gap as I thought they should be right being a set (oops). Should I use mineral oil or stay with synthetic? I had already drilled out the main jet earlier to 1mm then soldered it back to about .85 (sewing needle and vernier calipers) so drilling out again won't bother me, just need to find the correct size.

[Shaka]

Congrats on the install!  Seizing doesn't sound good though!   I run premix at about 37:1 of full synthetic.  For the break in period don't use synthetic though.  I also removed my oil pump, which was a bit of a pain, got if figured out now though!  If you have any questions on how to I can help you out there!  I'm not sure why you might be seizing.  Zombie's idea of the ring gap sounds good.  Otherwise, make sure she's getting enough oil and you may also need to go colder on your spark plug.  Stock spec is a 7, I went from an 8 in my stock cylinder to a 9 in the new aluminum one.  Definitely do lots of plug chops!  You don't want to damage your new set-up!  I made the mistake of not having the oil line hooked to the new carb right on mine and took a small piece of my brand new cylinder plating off!  Damage can occur very quickly while trying to tune a new set up!  Good luck!

[zombie]

What Shaka said... I run oil in the tank, and use the pump too. Zip tie the pump for break in, and run it normal after that. I'm not really sure about changing 2t oil for break in. I never have done that. For a box new rebuild it makes sense, but for a piston/jug? You just may be too lean, and that is causing the sieze. Better to foul plugs than jugs. Pull the jug, and see where the siezing is happening. Most likely near the exhaust port. check the ring gap, and polish out any glazing w/ 600 grit emory paper. 85 sounds a little lite on the main. I have a different carb.( Delorto 28mm ) and started w/ 120 main. I think I am running 140-44 right now. I think you should be around 90-110. Also richen up the idle circuit because when you close the throttle after running at/near full, you have lots of rpm's and no fuel to keep the piston cool. The idle should be set to where you can hear the engine running at de- accell. If it is too lean the engine will be silent, and the overheat is beginning. Shaka will tell you ... Our scoots will just about foul out at idle, and run rich untill the main come in. It's the only way to keep a 70cc alive that I have found. (modded 70cc)

[sidthesloth]

G'Day zombie, thanks for the info, I have got the covers off, but have ducked out for a coffee with the missus and to find an exhaust gasket. will check the cylinder within the hour, hope I have not done any damage, another lesson learnt, no short cuts.

[Shaka]

I'm running an Arreche 19mm carb w/ K&N filter.  I currently have a 25 pilot jet and 110 main.  I think the needle is in the middle clip position.  I was running a 20 pilot, 115 main before I installed a larger manifold and reed block.  I still have some tuning to do, I think I may try a 105 main jet, it seems I'm pretty rich!  I'm only getting about 30 mpg at best!  I also just got my reduction gears installed yesterday, so it's back to tuning all over again!   I'm waiting on finishing my leak-down tester to really get into the carb tuning.  I'm getting an easy 54 mph out of her now!  I haven't had a chance to really get out and let her rip yet, but I'm sure there is some more to be had in the fine tuning!

[sidthesloth]

G'Day shaka, I'm a long way off increasing the carb. size, I have just pulled the cylinder of and found the ring end gap to be 008", or 0.20mm. The bore is marked but not damaged but the piston has some heat/friction marks on it. I will try to get some pics. up. Do you think it would be worth running a cylinder hone through it? or should I just persevere with increased oil? As I said, I will be hounding for info.

[sidthesloth]

Hi, I'm trying to post some pics of the piston and cylinder, an excercise of frustration, see how this one goes. Piston.

[sidthesloth]

Aaaannd, Here is the cylinder.

[Shaka]

That's a big piston!  It doesn't look too bad!  It appears that the center of the piston is expanding and seizing.  I'm not certain on this, but maybe you could open up, or cut some windows in the skirt on the boost port side to help with cooling the underside?  Seek second opinion first!   Otherwise, you can take some real fine sandpaper and smooth the piston back out.  Is your cylinder aluminum or cast iron?  I wouldn't worry too much about honing it unless it has some deep scoring.  Most aluminum cylinders are plated so you can't really hone them.  I can't really tell from the pic what you have, but my guess is cast iron.  That may also be working against you with the expansion rates of two different metals.  At a minimum, take some fine sandpaper to the piston and run a couple plug chops.  Make sure you let the scoot idle for a bit to warm up the engine before riding, especially if you have a cast iron cylinder.

[zombie]

Looks like a lean mix, and light on the 2t oil. You can go around the piston w/ some emory cloth. Not up and down but around. Same w/ the jug. If there is any aluminum cast onto the jug you can use HCL, or Hydrochloric acid to melt it off. It only takes 4-5 seconds to work. The end gap is a tiny bit on the large side but is ok. A quick clean up, open the oil pump, add some 2t to the tank, and open the main jet. That should get you going. Looks like a nice clean cylinder for off the shelf. Did they send any tech info. on timing, or power band! I'm very curious!

[sidthesloth]

Hi, I didnt use any emery cloth but I did go and buy a hone and ran that through using 2t oil. They sent no info at all, just the parts, they did semd a new piston pin bearing which was not in the listing(bonus).

[Shaka]

Make sure you clean up the cylinder also!

[sidthesloth]

Sorry about the poor photos. The hone cleaned the cylinder up quite nice. Tomorrow will drill out the main jet to 1mm. I have added 100mls. of 2t oil to the tank and filled up with 95RON. Off to work now so will have to wait until tomorrow, (will log on via mobile phone)

[sidthesloth]

Zombie as I said they sent no info but if you like it was from ebaymotors.com, autotech355, is a honda dio big bore 82cc cylinder kit. Hope that helps. (hope I didn't breach any rules with that).

[zombie]

RULES???!!!??? WHA? It's all good. That's why the forum is here, to share Info.. You increased your capacity by almost a third, so you have to do the same with your fuel/air. The stock carb will get you enough fuel w/ re-jetting to keep the combustion temp. in line but you will never get enough air to take advantage of the jug. I' am running a 28mm Delorto carb on a 70cc kit. You will need to find something around 20-28mm depending on how far you want to mod the scoot. You will most likely wind up around 1.5mm on the main, and 40-44 on the pilot. You will also need either a full flo filter or a heavily modded air box to get a decent set up until you replace the carb.