07 s250 Strange problem fuel or spark related

[josephthediviner]

Check your carb diaphragm open the access cover in the met in box and carefully remove the two screws holding the cap on top of the carb remove the cap and long return spring then carefully lift the diaphragm unit out look closely and see if there are any holes or tears evident the replacement is very simple and inside the canister there is what looks to be a plastic screw slightly depress this while turning 1/6 turn and it will unlock the cam releasing the diaphragm from the body be careful not to drop either the little spring or needle to put it together again with new diaphragm use small pair of needle nose to hold screw upright holding canister upside down by needle lower canister over the screw spring assy and when in place either turn slightly to start cam or carefully turn over and use screwdriver to set cam that's all install into carb body carefully setting top into rib and add cover.       

[ifican]

Someone previously said to check diaphragm as well, plan too just havent gotten around to it. As for the leak right after put back together was spraying carb cleaner while engine was idling around boot and throttle arm and idle would choke as gasp. Was a fluke actually finding it cause didnt think to check. Would do it almost every time. Though i was chatting with my neighbor trying to get it to do it again this evening and could not so who knows. Ill try to get at the diaphragm when i get a chance, but honestly probably not going to be for a good week. To many higher priority things going on right now. But we will see.....

[zombie]

  What could possibly be more important than your Kymco Scooter?

[mrbios]

It sounds like your scoot has multiple problems.  CDI - no.  Valves - no.  Ethanol gas - no, I run Costco gas all the time with no issues. 

Carburetor - Yes, multiple issues.
The high idle is a sign of a vacuum leak.  When the boots on the carb are tightened enough you shouldn't be able to move the carb.  If you can move the carb because it is slipping in the boots then the clamp needs to be tightened.

Off idle hesitation - pilot jet & pilot circuit is clogged.  You can clean the pilot jet but you must also clean the passage that the gas travels through before it gets to the carb.  Unlike the main jet which delivers gas directly into the air stream.  Another sign is things ran good while cold - the electric choke will mask the lack of fuel at low speed until the scooter warms up and the electric choke stops delivering extra fuel.

Top speed issues:
Probably the vacuum piston / vacuum slide - the big rubber diaphragm is leaking or not sealed properly.  If it leaks even a tiny bit top speed is limited to about 45mph.

Muffler - possible leak.  If you get a leak and loose back pressure you will very quickly loose lots of power.  Rattles are a result of poor welding of the internal baffle that I call the Hot Dog in many of Kymco's mufflers made in a certain time period.  I had to open my exhaust and remove the loose part and weld it shut so did another guy on the forum from (Romania?).

Consider watching my carb videos for more info on the pilot jet cleaning.

Carburetor Cleaning Part I   
Carburetor Cleaning Part II   
Carburetor Cleaning Part III   

[ifican]

Great videos thx, the diaphragm looks good. Pulled it inspected and put back, seemed that there was alot of play in the throtte needle but been so long since i had a carb partially apart i forget. Put back together and no real change in how it runs. Next task i think is going to be pulling the carb completely and going over it all. As in the video whats the easiest way to clean the pilot fuel passage. Also does anyone have a surfire way to test or tell if its fuel or spark. Feels and acts like fuel but i have seen spark in the past cause weird issues as well..

[zombie]

Clogged idle circuit or non functional choke. Just my guesses.



A can of Carb clean will blow out the passage, and these help clean all the tiny ports...

http://www.homedepot.com/p/Lincoln-Electric-Oxygen-Acetylene-Torch-Tip-Cleaner-Kit-KH575/100341101

Have you tried adjusting the idle mix screw? You should be able to stall the bike with it if it is working.

[mrbios]

Clogged idle circuit or non functional choke. Just my guesses.

Interesting video.  At first I thought nothing was happening..

[ifican]

Ok finally got some time so just now pull the carb completely out and basically stripped it. Sprayed a little cleaner in all ports and made sure it was minimally dripping out somewhere. Put it all back together and it runs much better. I need to take it on a few longer rides and a few highway jaunts but it seems much better already. I still think there may be a minor vacuum leak somewhere and the carb may need a good soaking as prelimary minor clean seems to have made a difference. More to come in the next couple weeks as i get some time put on it and we see how it behaves.

[mrbios]

... prelimary minor clean seems to have made a difference. More to come in the next couple weeks as i get some time put on it and we see how it behaves.

I just updated the video links.  I used the technique in Carb Cleaning Part III where the plug is drilled to access the pilot jet passage.  The Keihin Carb uses the tinyest passage I have ever seen.  I recommend increasing the pilot jet to #48.  You wont believe the difference it makes and mpg is the same. 

[zombie]

 

[ifican]

Ok more good times. Pilot jet and fuel passages seem clean. Looked over carb again today, perhaps the light was better than before but found a small tear in the diaphragm that i did not see earlier. I have a hard time believing that tiny tear could be causing all the erratic behavior but we will see. Will update once i get part in and get it changed out.

A question why i am at it. While searching around i cannot find just the diaphragm. Only part 16019 which seems to be the vacuum piston and diaphragm together. Is that common?

[zombie]

Whatever mm the carb bore measures. my guess... 32mm ish. Order a whole new carb fo like 50 bucks

[ifican]

Actually thought about this and as i was looking couldnt find an exact match. The oem carb is close to 250 with shipping and lots of others that look like they would work in the 150-185 range with a couple right about 80 that i could probably make work but would take some tinkering at least from the pic.

[zombie]

It's a 30mm CVK Carb. There are a couple here... http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.H0.X30mm+cvk+carb&_nkw=30mm+cvk+carb&_sacat=0&_from=R40

All you really have to do is swap out you jets into the new carb.

This place has the diaphragm but it is 37.50 by itself... http://www.kymcopartsmonster.com/p/Kymco-Parts#/Kymco_USA/BA50AB_People_S_250/Carburetor/2K03080005/2K03080031

[ifican]

Thanks for this, i had already ordered the part i needed, if that does not work i will be looking back at these. Either way will advise for anyone following one way or the other.