dellorto 21mm problem

i have problem with my dellorto 21mm karb.. on my polini evo & c21 setup.. main jet is 93 and other jet (dont know name on english) is 40.. on the full throttle works fine but when i start on half throttle sound is terrible and scooter wont go as he should be... goes fine only on full throttle..

too small jett

which jet? pilot or main? WOuldnt it run fine at WOT if the main was ok?

1/2 throttle could be the needle along with the pilot.

str8dum said:

which jet? pilot or main? WOuldnt it run fine at WOT if the main was ok?

1/2 throttle could be the needle along with the pilot.

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I agree. If I can only figure out how to post my jetting chart.

After setting the main the needle position and then the needle jet are the next biggest adjustments to be made. Try lowering the needle first. If the needle was too low it would spin the motor fast but have no "balls" under load. If it is rich it would spin slow between mid to 3/4 throttle but under load pull like a tractor but not pick up rpm fast. The last items to tune are the air correction screw and pilot jet. They make sure the thing responds when the throttle is whacked open from nothing.

Often once you have done the whole thing you have to go back over it once more to fine tune it again. But the key is always main first!! Work from full open and full rpm down to 3/4 throttle and so on.

well it could be the problem of jetting, but i think its the problem of the ignition and low rpms, i say this because my friend has an am6 bike and we were mounting an mk prorace 2 cyl on with his standard igition. on low revs (half throttle) it sounds terrible, no power but once you give the full throttle the bike wheelies up to 4th gear...i was reading the manual booklet of the pr2 and it recommends a competition ignition...he is soon getting the pvl digital variable and his problem will be solved..
maybe this might be your problem, that if you have a standard ignition on it might not be good for your setup.

Mr.Aerox said:

well it could be the problem of jetting, but i think its the problem of the ignition and low rpms, i say this because my friend has an am6 bike and we were mounting an mk prorace 2 cyl on with his standard igition. on low revs (half throttle) it sounds terrible, no power but once you give the full throttle the bike wheelies up to 4th gear...i was reading the manual booklet of the pr2 and it recommends a competition ignition...he is soon getting the pvl digital variable and his problem will be solved..
maybe this might be your problem, that if you have a standard ignition on it might not be good for your setup.

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ignition is polini inerrotor

alonso said:

i have problem with my dellorto 21mm karb.. on my polini evo & c21 setup.. main jet is 93 and other jet (dont know name on english) is 40.. on the full throttle works fine but when i start on half throttle sound is terrible and scooter wont go as he should be... goes fine only on full throttle..

Click to expand...

Why don't you try main jet-98, then the idle/mixture jet-45...Your jettings are too small for your setup...