My Aprilia rs 125, 2001 model is poorly, can anyone help?

Question

My bike starts fine, goes fine, rides fines, until i put the petrol in the 'on' position properly. It's running perfectly on reserve everywhere but as soon as i turn the tap 'on' to the main it judders, loses all sign of revs and dies then won't start back up without the choke on, so i am having to ride in reserve everywhere;

What could this be? (blockage maybe?)

Is it an Easy fix? (pour some cleaner into the petrol?)

and yes it has plenty of petrol in it.

also could it damage my bike riding in reserve all the time.

Please help.

Answer 1

take off the tank drain the fuel, turn it upside down unscrew the tap and pull out the tap you will have a long filter attached to it with a cut off for the reserve mine did the same mines an af1 125 but they are the same in the tanks you may have alot of rust build up around the filter in your tank take out and clean as i say.

Answer 2

just for curiosity's sake, which way are you turning it? up or downwards?

if you're positive it's on the right way, the only thing i can think of is the fuel path for the on position is blocked, while the reserve path is not....absolutely nothing about the delivery system itsself, nor the fuel/air mixture changes with that switch, so there's not a whole lot of possible reasons why it would work in one, and not the other.

Answer 3

I would just bypass the shut off valve.

Answer 4

Were you having trouble all allong since new? If so I would suspect a pluged or defective valve. And for your question about harming the bike the answer is a flat no. The only trouble that it could cause is a walk to get more gas. Hope this helped.