Intermittent Starting Issue '73TX650

[Chrondor]

Hey guys,
I was hoping you could give me some insight into an intermittent starting issue I'm having.
It usually occurs after it is all warmed up and I go to a store or something for 10 minutes and when I come out it won't kick start and I have to pop it. After I get it going it runs normal.The bike is a '73 TX650 and the carbs are all sparkly with good floats and new float needle valve. Battery is "a" okay at 12.7v and starts up fine when I first get her going. Left plug is perfect and right a bit dark but not horrible. Running Pamco points and e-advance unit Any ideas are much appreciated.
-Chrondor

 

[TwoManyXS1Bs]

Sounds like it may be hot soaking, fuel vaporizing after a run's shutdown, makes it rich during restart.

Try this. At almost exactly right after you shut off ignition, while the engine is spinning down, crack the throttle 1/4 turn. This'll lean out the intakes and clear the carbs. If it starts better afterwards, consider that your idle mix is too rich, or that you're still running on "Winter" fuel, which has a higher Reid vapor pressure (evaporates more easily) to counter the cold weather...

 

[Jim]

Sounds like it may be hot soaking, fuel vaporizing after a run's shutdown, makes it rich during restart.

Yeah... does sound like a vapor lock. Another way to find out is to get crazy with the throttle. Make the same trip. When you start it, hold the throttle at least halfway open and see if it lights off. Not near as effective with the CV carbs, but worth a try....

 

[gggGary]

Try shutting off your petcocks before you shut off the motor, if this works well, your float valves are leaking.

 

[Chrondor]

All good ideas. I'll try them out this week and let you know which is the culprit.