Hard to start when cold but runs fine otherwise

[shortman1166]

I can not seem to get my scooter to start for like an hour after work in the morning when its around 40-50 overnight. Once it is running for a minute or two it is fine for the rest of the day and runs great, but it is just getting that initial start. I have changed the carb to a non sealed one which had a new choke on it and also put a slightly bigger pilot jet on it. It seems that it does better when the gas cap is off, the pressure is released. It makes a very loud hissing noise when it is usually removed. Also I notice a "gurgling" sound coming from the tank when I am trying to start it in the morning if the cap is left on. Could it be a bad gas cap restricting the gas flow initially? Please help this is getting very frustrating. I have changed the spark plug to an Iridium and makes a good spark, I checked the valves and have them set to .004 intake and .005 exhaust. Doing a hand check on the kick start there seems to be good compression, I don't have a compression tester. But like I said once it is going it will run all day no problem and starts right back up even if left for a couple hours. Its just the initial cold start after 12 hours or so at work overnight.

[scootnewb]

Something that helped my cold start problem was related to the valves and carb tuning.

Those valve clearance settings you're using - .004 and .005 inches for exhaust were too much for my scoot. I used the values listed on the metal plate in front for the seat. Between .05mm and .03mm. My valve clatter went away and it starts right up now.

Check that plate and see if you have a suggested valve clearance listed.

[shortman1166]

I changed the valves to .002 and .0025 for the intake and exhaust... They are within the spec on the plate listed now so I will try in the morning and see if it solves the problem. I started it briefly and it fired right up but it has not sat all night yet. It was cold when I worked on it but I did drive it this morning. Hopefully it was that easy to fix..

[GrumpyUnk]

Try removing the gas cap for a few seconds, then replacing it. That will allow any vacuum to dissipate, and fuel should flow freely. If that 'fixes' it, check the cap for proper venting. Some have a vent tube at the top of the tank that connects to a vacuum operated valve that is apparently a 'fuel vapor fume catcher' system. IOW an emissions device.
Alternatively, take the machine across the river to W Laff, and have a PU engineer or gearhead take a look. Pretty smaht people go there, I did. Well, maybe not so smart now. I dunno, been gone for years.
Maybe check in the dorms for some undergrad who fiddles with these things.
tom