I did not investigate since I last drove it in June (there is only one "race event" here in France ), but I had the same problem on my racer every lap while I was racing:

After the straigth line where I could push the 3rd and the short 4th, there were a big U turn on the left, so massive braking just before... Everytime I was pushing hard, I had "no fuel" after the first corner :plemplem: and when I was not pushing the 4th to high-rev, it was okay...

Does anyone have ever had some "filling" problem with the KOSO ? Or do I have to blame my tank ? Or my engine is too *powerfull* ?

We are talking about this cutty :love: :

http://ktylife.free.fr/vespa/KTy133/AntoineVespaRacing4.jpg

Might be a problem with the gasoline level in the float bowl. Quite common with koso carbs, as there is a slim plate defining that level, wich is easily bent by accident. This leads to either overflow or drainage of the float bowl. Readjusting that plate might be the solution of your problem...

you can always check the flow from the tank through the fuel pipe into the carb bowl.

your ratio should be above 200-250 ml / minute to maintain proper fuel delivery into the carb bowl.

if your koso doesn't meet this requirement, try enlarging the fuel ports in the carburettor body.

Thanks, I'll check this out...

if you're only runnig it once a year or so, better check your fuel tap, too. with your carb utterly below the level of your tank, there should never be any use for a fuel pump.

Have a look at that: Klick and pic

Have a look at that: Klick and pic

Okay, I'll try to figure out what is important on this picture :)

and now take a look at your carb

Bearbeitet 19. September 200619 Jr. von Werner Amort

Is this some sort of "security" to make sure there is always enough fuel ?? :plemplem:

no, more likely this is used to have fuel flow MORE into the bowl.

similar to my tip. but I enlarged the complete drilled bore from filter to the bowl in my carb. this lead to 15% more fuel flow into the bowl. how much, you can just try with your equipment.

Bearbeitet 19. September 200619 Jr. von oli-san