Kymco 250cc LC idle issues/WOT cut out

[Deleted]

In the last few weeks, my scooter seems to have some idling issues, cold start rough idle and then when good and warm seems to idle fast intermittently, especially after a good highway run, fast enough to drag the clutch a bit sometimes. Then on a couple of WOT runs at 70 plus the engine sputtered a bit and cut out, but ran as strong as ever at 65.

Haven't adjusted anything yet because it looks like a major pain is involved removing the rear cover, and I honesty can't even begin to visualize that task, looks like screws that need to come out are blocked by other things etc. I suspect a combination of the idle adjustment and possibly enricher and getting time for a valve adjustment, any thoughts?

[gsx600racer]

My guess would be maybe a air leak or crud in the carb(blocked jets).

If its a air leak, the auto enricher/choke could be compensating till its warmed up then running lean once the auto enricher/choke closes.(aka high revs)

If its clogged jets, the same may hold true with the auto enricher/choke compensating for the blockage and possible lean condition once its warmed up and idling high.

As for the WOT cutout, I am guessing fuel starvation or maybe running lean and entering soft seize territory . I know being L/C the odds of seizing are less, but I would not rule it out. 

I would also do a compression test and check the plug.

[90GTVert]

Get a service manual if at all possible. I use mine when removing panels on the TMAX because it shows what order panels need to be removed and I can look at what kinds of fasteners are used. Not sure if your Kymco will be the same way, but some of my panels feel like they could break by the time they release. Definitely makes it an uneasy process the first time around even with the manual, but at least I know I'm not pulling on something to try and unsnap it when there's actually a different type of fastener used. The service manual should also have some troubleshooting help.

Vacuum leaks commonly cause high or surging idles.

Running lean/hot can make the idle hang. A thorough carb cleaning would be a good step. Then possible idle mixture settings. With my small scoots, as long as I know the main jet tune is good I richen the idle mixture till the engine stops hanging after it gets hot from a WOT pass. In your case though, it's been running alright before so I would look for a leak or carb issue before just making the adjustment.

[Deleted]

So far I found one connection on the intake that was pretty soft, to the point where I could pull it off even with the spring clip with not much effort, clipped it to good rubber and there was a noticeable improvement but still not right.

I have a suspicion that when the dealer pulled the carb last year, they did not use a gasket on the intake, but that's for a rainy day.

I will say I've ran it hard on some high 80, low 90s days and it doesn't appear to run hot, the cooling fan has only kicked in a few times and it definitely is rich on a cold start.

I do have the manual, just not very clear on body panel removals. But according to the maintenance schedule it's due for a valve check so I guess we're going to learn and if I break the plastic, it'still available and not ungodly expensive.

[90GTVert]

Even the Yamaha manual doesn't tell step by step on the panels. It basically just has some sections of panels labeled with numbers for order and then drawings that can be examined to figure out what fasteners are where. It still takes some head scratching to be certain you're on the right track. Not simple like the little Chinese scoots, but at least panels aren't cracking and falling off on their own. Good luck with it. Give yourself plenty of time to do the job and hopefully it'll go better than you expect.

[Deleted]

Well we have two days of storms, and the Jeep is back at the shop for brake work, so I pulled up the manual and with a bit of patience, I got the rear cover off without breaking anything, and I went ahead and took off the rockers too, the left one was ground completely through in the crash and the right was already scuffed good.

[Deleted]

Got the valve cover off, there was absolutely NO clearance on either valve, Kymco specifies .1mm on intake and exhaust and they were tight as heck so we fixed that, now for a lunch break and then put the vale cover back on and see what we get.

[gsx600racer]

Jun 16, 2017 11:57:13 GMT -5 peascreek said:

Got the valve cover off, there was absolutely NO clearance on either valve, Kymco specifies .1mm on intake and exhaust and they were tight as heck so we fixed that, now for a lunch break and then put the vale cover back on and see what we get.

I am surprised with the valves that tight that you didn't have starting issues. Hopefully you are closer to the solution with the valves adjusted. 

It just strikes me as being weird that over time your valve lash got tighter vs looser and the miles added up, or they were super tight to begin with. 

[Deleted]

Got the valve cover back on, started right up, put the seat/bucket back on and took for a short spin, very short since no taillights or plates without the body cover, but it ran good, idle is good, have to wait to really get it out for a run, but I think the valves were the issue, makes sense, it was 2000 miles past the check point... the stupid thing is my spark plug socket doesn't fit the Kymco so I can't check it, and the tach isn't working right now for some reason so I adjusted by wheel spin for now.