Running on choke

I know I have a PK, and not many of you in this group have one, but the principal of this problem is probably relevant to most of you.

I have what appears to be a fuel starvation problem, but is confusing, because the scoot will work with the choke out. I had a guy look at it and he thought my problem was one of over heating due to too much oil in the petrol tank. He cleaned out the carb several times and had it running sweet. My petrol was low, so I filled up the tank with 5 litres of petrol. I then put in a 100ml bottle of 2 stroke oil which had sufficient for 5 litres at 2%. This is as far as I can tell correct. I got five miles down the road and the fuel starvation problem started again. I have had a look at the fuel pipe and think it may have been routing rather long and high. I took 10mm off the pipe and made sure there were no obstructions and refitted it. no joy

I took off the fuel tank and checked the fuel tap seal. this had some chunks scored out of it and loose rubber behind the fuel tap connector that may have been restricting some of the fuel.

I emptied the fuel into a can and noticed there was some rubber in the can. Therefore some rubber may be in the carb as well, but it works on the choke.

Question: Why if I appear to have fuel starvation, will it get me home on the choke?

All ideas are welcome, 'cos this is getting me down and running my whole enjoyment of having a scoot, especially with the wife nagging me about the ornament in the garage!!


You might have an air leak, this obviously affects the mixture so might cause the same problems as you have described, I had a problem with my T5 and it ran with the choke fully out sounding great but died when it was in,but i ended up with a new carb as i had basically wrecked mine by crossthreading the mixture screw,doh.

The reason why it will run with the choke on is because when you pull the choke out it releases a rubber bung that is blocking off the choke jet so you are now getting fuel running through this jet as well as the main jet… if you have an air leak somewhere this will effectively ricken up the mixture so that you have it closer to the correct fuel/air mix. What I would check first would be the main jet though. It is likely that this is blocked. When you pull the choke out you are letting that extra fuel through, so that even if the main jet is blocked you are approximating the correct mix. Make sure that the float in the carb isn’t sticking in the up position. Next time it starves turn the fuel off immediately, stop and check to see if there is any fuel in the float bowl… that should narrow your problem down. If it not full then you DO have a fuel starving prob. If it’s not it must be an air leak (through the seals or at the carb manifold).

Hope this helps