Engine starts, races, idles, dies

[natetheokay]

Hi there, I have a 4-stroke qmb139 Peace Verona 50cc with about 300 miles on it. When I start the engine via the electric start, it idles very fast, then the revs drop so low after a minute or two that the engine dies unless I open up the throttle. If I do that for several minutes until it warms up, it'll idle without dying, this has been in cool weather (30's-50's). This is assuming it will start at all, many times (especially after not riding it for the weekend or when it's especially cold), it won't start at all, though it turns over.

Here's what i've tried so far (both for fun and to try to fix the above):

New fuel line and fuel filter
Replaced stock coil and spark plug with orange coil and NGK plug
Replaced stock cdi with unrestricted CDI
Installed lighter sliders
Replaced enricher/choke
Installed tiny-tach and bike computer

I've also adjusted the carburetor and idle screw numerous times to try to fix the problem, but opening up the throttle for several minutes is the only thing that seems to work consistently.

Any other suggestions to improve starting and keep the thing from dying?

[millsc]

Try a bigger idle jet and adjust the valves.

[natetheokay]

I'll give the valve adjustment a try and report back.

[millsc]

valve adjustment does wonders

[yosemite]

Don't worry about a bigger PILOT JET unless you put in a V8, but do adjust your valves. Running and dying with low rpms is a sure sign of tight valves and will not hold low rpms due to valve staying a little open and looseing compression.
Sam

[inuyasha]

Hi
I agree with Sam and Millsc Give her a valve adjustment any wheres from .003 to .005 is a good place to start
Take care and ride safely
Yours Hank

[natetheokay]

All right, finished adjusting valves. According to the VIN plate on it, intake should be .06mm and exhaust .08mm. My closest feeler gauges were .064mm and .076mm. First time to adjust the valves, but I tightened them until they gripped the gauge fairly tightly but I didn't have to struggle to remove them.

Unfortunately, the scoot won't start at all now. I checked for spark and that's good, it still turns over but it won't sustain itself. Besides the .06mm and .08mm I also tried the .05mm suggested in other valve adjusting posts. Assuming I did okay with the valves (no guarantee on that, given my newb skillz), anything else I might be missing I should try before taking her into the shop (it's still under warranty)?

Btw, thanks for all the help, it's been quite the adventure with this thing.

[natetheokay]

Well, stupid me, the reason the scoot wouldn't start was the battery had gone kaput . Just enough juice to give spark, but not enough to start 'er up. Swapped out the battery and it's starting just fine and the revs seem to be holding steady now.

[skuttadawg]

Any auto part store should have feeler gauges for valves since they are bent to fit in there instead of flat