My 101 dies after warmup

[joe]

Hello,
this is my first post here, bought an '08 101 this spring, enjoyed riding it, despite poor compression and tough starting. I got that addressed last month when a mechanic FINALLY diagnosed my problem as bad valves, and replaced them. Smooth starting and running after that, until....

TWO weeks later, the scoot dies about 2 minutes after startup, winds down like it's running low on fuel, and won't start again.

After I pushed it home, I put a new spark plug in and it started right away, idled rough for a bit, and then died again in the same way after a couple minutes of idle/riding around slowly.
It seems like once it cools down it will restart, run for a couple of minutes, sputter and die. Each time I restart it after that, it will run for less and less time until it just won't idle anymore. Then I let it cool down and repeat the process all over again. I've been checking and wiping off the plug every once in a while, but I think I've eliminated that as a cause.

So I'm looking at the following approaches before I call this mechanic again, I'm tired of the drama with this dumb scoot.

Hypothesis, in order of perceived likelihood:

Idle/Carb setting too low?
bad gas/ water in gas?
Autochoke issue?
CDI issue?
Fuel Filter?

Thanks to the time change and cold wave here in Colorado, I'm probably not going to take another crack at this until the weekend, but I'd appreciate any suggestions or input, thanks!

Joe

[harry]

add a dirty/clogged idle jet to your list

try some gas drier in the tank like "iso-heat" or "heet"

try removing the gas cap and see if will stay running 
sometimes the breather hole gets clogged

fuel flow might be the issue too 
remove the vacuum & gas  line from the carb and suck on
the vac line you should have a good flow of fuel

 oilyhans

[joe]

Thanks for the reply, Harry.

 So I cleaned the air filter, cleaned out the gas cap, and added heet yesterday, it idled well for about 4 minutes and cut off again, running for less time every time I restarted.

This led me to make the observation that once the enricher kicks in, the fuel cuts out.

After this I decided to take the plunge and disconnect the carb. I took it apart and let it soak in gas, then sprayed everything down with cleaner and compressed air. I even sacrificed my high E string to clean out the jets! I felt like a good amount of stuff came out of the carb, but nothing really offensive or gunky.
I drained the gas tank and reassembled the carb to the airbox, and then reinstalled the vac and fuel lines, checked the fuel filter here, too. It looked fine.
New gas, new plug, real tough starting. It runs after about 10 kicks and idled strongly for about 3 minutes, until bam, you guessed it, cut out.

 

So now, I'm thinking the culprit may be fuel flow, although I don't really understand the concept of sucking on the vac line If I do this should I be able to draw fuel (to my mouth, presumably)? I suppose I'll take a better look at the petcock, that's right under the fuel tank, right?

I may have to to a bit of night work this week, I hate wasting my weekend wrenching my scoot instead or riding it!

[harry]

ewwwwue , if you get gas in your mouth you will puke!
on the fuel shutoff there are 3 ports
fuel in, fuel out and vac line .the vac line is on the other side of the
of the fuel flow and has diaphragm that opens when under vacuum
opening the flow of fuel though the gas in & gas out.

carb should be 1/2 to 1 1/2 turns out  depending where you live
be it the mile high city Denver or sea level  .

as for the auto choke, when you turn on the key the current goes to the
 AC  warming up the thermal wax allowing the spring to act on the plunger
it takes about 3 mins for the AC to stop working, though there is still
 power going to it as the wax needs to be kept hot.

look elsewhere on this site for the how test the auto choke that i've previously  posted.

you might want to check for air leaks in the intake system by spraying
carb cleaner on the joints & mating surfaces of parts   if the motor reves up
you have a leak.

oilyhans