Why is my S3 such a nightmare to start?

[muffster]

After it's been left for a few weeks i can't get it to start.
It's a resto on an Li. Newly built 175 conversion. ScootRS exhaust, 22mm jetex. air scoop is on. After much fettling it has been running sweet but being in the forces i don't get as much time as i would like to get it sorted.
Anyway today i had to warm the plug up with a heat gun to get it to start, then it wouldn't run when i turned the choke back off and needed tweaking to keep it running.
Obviously i can't carry on like this when i actually start using it so what the hell is going on?
Any ideas?

Thanks.

[ForemanBob]

To start a Scooter needs

Fuel Air mixture
Compression
Spark

with any of these in short supply you will have problems.

Check for the obvious things first.... Is your choke actually working on your carb, do you have a blockage in the choke circuit

If it's newly built have you rechecked the cylinder head is torqued down tight.

Have you tried changing to a new spark plug.....

[Daggs]

What is the carb. jetting? Have you broken out the bridge in the air-scoop?

[corrado]

Is fuel reaching the plug? Was the plug wet when you took it out to heat up? Is the plug gap set correctly? Ie, 20 tho .. 0.5mm?

[vRSG60]

Check for the obvious things first.... Is your choke actually working on your carb, do you have a blockage in the choke circuit...

My Li125 was easy to start cold but a bugger when warmed up. The choke plunger was stuck in the "on" position.

[FREAK]

ive just had the same prob with a gp 200 ive just rebuilt , after changing the stator and re setting the ignition new cdi new plug new ht lead etc etc ,turned out to be the crap jettex ,put another on and its fine now BUT ide recomend putting a phbl on :fb:

[muffster]

Ok, it's got fuel and spark, can't be 100% about the air mixture???
The plug was wet when i took it out. Electronic kit is brand new. Not tried the cylinder head but it hasn't even covered a mile yet!
carb is 22mm jetex and i have changed the jets, can't remeber exactly what they are off the top of my head!!
When i initially got it running after the rebuild i took the air scoop off and it ran well but after lots of fettling i put the scoop back on and it was fine. I will take the bridge out of the scoop tomorrow and see how it does.
Choke is working fine, i can see it clearly with the rubber hose off.
How do i tell if the air flow is sufficent?

Many thanks.

[Daggs]

With the scoop bridge removed and using a standard air-box, you will need a 45 pilot jet. Sometimes you may need to go up or down 1 or 2 on the pilot. But 45 is a good starting point.
Jetex carbs get a lot of bad press. In my opinion it's more often failure to set them up correctly, not the carb. itself.

[Adam_Winstone]

What plug have you got fitted? Try an NGK B7ES and close the plug gap slightly and see if this helps. You shouldn't need to do this if all is well but it might make your starting a little easier.

Sadly, this could be the result of about 101 things that could be wrong with it. You need to systematically go through and cross potential causes off the list.

Adam

[squeakmillward]

try some fresh fuel