Hi, Hit a problem with my lads Speedfight 2 50cc AC, original Gurtner carb u/s, bought one of the standard replacement ones with a 72 main jet (chinese(?) one at £30) , set up the needle as per existing, checked the existing fuel level in the bowl (approx 1mm below the gasket) and adjusted up the new one to match. Engine starts and runs sweetly but dies away after 3-4 minutes running as though its running out of fuel, bypassed the vacumn tap with an auxiliary tank and still the same, if I take the the bowl off and just allow fuel to run through the float valve I can see no issue and it shuts off smoothly. Any suggestions as to cause? Otherwise I going to have to see if can get a genuine Peugeot part if I can, ouch! Thanks Mike
this but also grab the old carb and pull out the main jet in it, check its a 71 jet installed in the old carb. autochoke scuba ? 4-5 mins is about enough time for the autochoke to kick in heat up and close off, maybe throwing bike into a to lean air mix and it stalling out, if it fails to restart right away it could be down to the autochoke still closed off and not fully open giving that extra air input ? double check your seal to the carb and inlet manifold just incase its split or you have a slight leak from a failing gasket seal.
I would be thinking fuel starvation, or possible cylinder/rings are a bit dead. Why did you change the whole carb?
Replaced the carb due to the throttle slide being v.v loose i.e. worn out giving poor throttling. Old main jet 72, new main jet 72, needle set as per original. It will restart but not throttle unless left for 10-15 minutes so perhaps something is sticking (noticed the new float valve has no plastic tip) , I'll put some clear tube on the drain and see if the fuel level drops while it's running. Re auto choke I'll pull it off and test it using a spare battery, will also test the original and use it if necessary. Thanks for the replies
