Scooter starting issue - quick question

Hi, speedfight 1, working on jets etc. The scooter really struggles to start but found if I hold hand over air intake then starts fine, so too lean when cold I presume. The question is therefore, do I rectify this with a larger main jet, adjust centre needle clip height, adjust air/fuel screw or look at auto enricher? Is there likely to be an obvious easy fix before I make changes to the wrong thing. Thanks

 

i wrote a guide, your carb needs cleaning and maybe your autochoke needs changing.

 

to sum up my guide instead of looking for it, whip off your float bowl, and there is a kinda long tube with a tiny brass jet pressed into it in the float bowl, thats the choke curcuit, that tiny jet gets blocked easily, spray some carb cleaner down there then blast it with compressed air, being careful not to blow the jet out. stick it all back together and see if it helps, also check your float bowl doesnt leak, this is common too, people ovetighten the drain screw and crack the float bowl (its plastic) and the fuel leaks out when its not running. if these are not your problems, change the autochoke

 

Hi, thanks. I've seen the guide which nicely clears up a number of uncertainties that I had. Carb was stripped, cleaned, dried and rebuilt with main jet one size smaller to try to lean it out a little as it guzzled fuel and smoked a lot. This led to this starting issue where I have to restrict the airbox to start it, and a high revving that takes a while to drop after deceleration. With only a main jet change I stand baffled by the issues. I figured that any lean mix at start and deceleration would be caused by the needle valve or idle jet, but these weren,t changed. Hence why I now seek advice. choke circuit sounds promising so I,ll try that first, maybe grit got in. Failing that I,ll put the larger jet back in and see what happens. I,m happy to play around but prefer getting advice here for a quicker route than my own messing. Thanks for taking the time to reply.

 

Putting your hand over the air intake at the back of the carb increases the vacuum pull and massively draws fuel into the chamber. This also indicates that it is not getting enough fuel or is getting too much air when cranking from cold. Put the air mix screw to one and a half turns out from fully in, put the standard size main jet back in, and the circlip on the needle to the middle slot. Then see how it starts. If it is still difficult, go to a lower slot, raising the needle allowing more fuel in a little. If it is still difficult with the needle on the very bottom slot, change the auto choke unit, (they are not expensive anyway), put the needle back to the middle slot, up-jet one size, and go through the process again.
Yes it is laborious, but it will come right.

 

Sounds like a good way to eliminate things. I,ve now checked the choke on a car battery and functions fine, sprayed carb cleaner throught the choke chamber so now I,ll try the needle and jet variations. Thanks for the advice guys.