What does the idlescrew and airmixturescrew do?

boheme · Nov 20, 2006

I tried to do a follow up on another thread..."starting with choke only"... but with no replys...

In that thread, have a look, kzoo describes how to set the carburettor to get a nice running motor... I guess its a good description... but as a newbie mechanic I understand nothing or very little of it... and of all the shortened words like "FS"... and what is fuelscrew?

Could somebody explain more specific how you adjust the carb from the outside... I know its a lot to do... and maybe the most important thing to on the inside like the jetneedles and stuff...

but right now I like to understand the outsideadjustments....

If I turn the airmixscrew in what happens.... more air...less.... and the same with idle... what happens?

And whatÃ‚Â´s "FS" and this fuelscrew?

As I understood it... you adjust the idle to a good level.. IÃ‚Â´ll do it by ear... and then adjust the airmix to max idling and then adjust the idle back to normal idling...
The engine should be warm...

Ok... you guys always seems to see what I mean, in despite of my often odd questioning type.... :lol:

So come on...

/Rikard

dsducati · Nov 20, 2006

Your FE501 from 2001 does not have an external air screw. It has an idle screw which mechanically stops the slide from falling completely allowing one to set the idle speed. In front of that is a small screw that sets your fuel mixture at idle. Set the idle screw and then turn the fuel mixture screw in and out slowly til revs are highest. Turn the idle screw down and have a go at the mixture screw again. If engine speed improves again, turn the idle screw down and have another go at the mixture screw. After 2-3 times you will have it. Fuel mixture screw is fed by the pilot. That helps one understand that if the mixture screw is only out 1/2 turn or so when finished the pilot jet is a bit big. If the screw is out 3 turns, pilot jet is a bit small. 1-2 turns out and all is fine. Good luck
dan

kzoo · Nov 20, 2006

boheme,

sorry for the late reply... Here is a guide to jetting the dellorto carb that I've read through a few time.

http://www.ducatimeccanica.com/dellorto ... lorto.html

boheme · Nov 20, 2006

Thanks guys....

but looking in my manual... it seems like to the right thereÃ‚Â´s this idlescrew...

then going to the left theres is this overflowtube....close down to the left of that owerflowtube thereÃ‚Â´s a small screw... that sort of goes into the carb....

and then to the left of that one thereÃ‚Â´s this next screw that rather seems to tighten the intake manifold...

:?:
and this the last described screw is, according to the manual, the mixturescrew... But to me it seems rather that its there to tighten the intakemanifold...

Correct me if IÃ‚Â´m wrong...
:idea:
And, in that case, what about the small screw, thatÃ‚Â´s between the mix and idlescrew I wrote about... Should I forget about that one for now?

/Rikard

Maddel · Nov 20, 2006

Your 2001 Owners Manual says:
The carburettor has an idling screw (Fig. 8C-1)
and a mixture screw (Fig. 8C-2) that have to be
properly adjusted.

The according image 8C in the 2001 Owners Manual
contains an error! No. 2 points to the hose clip 8O

I marked the mixture screw in the pic below.
.

boheme · Nov 21, 2006

THANKS! Then ÃƒÂ

dsducati · Nov 21, 2006

Dead on and yes it will affect how it starts. Now that you have the basics down, I'll add that I prefer to have the idle mixture screw at 1 turn with a larger pilot rather than at say 2 turns and a size smaller pilot. Explanation....Pilot jet supplies the idle mixture screw and ALSO a small orifice drilled under the engine side of the slide. Once the slide is raised slightly this orifice kicks in until the needle transition. The larger pilot supplies a bit more fuel coming off idle and helps throttle response a bit, helps eliminate lean flame outs, and reduces popping through the muffler. Don't go so far that the fuel screw is only out a hair or hard starting and sooted plugs becomes a problem.
dan

boheme · Nov 21, 2006

Thank you very much for a good explanation!

IÃ‚Â´ll try to set it up like that... and then while driving... if throttle answer in the very beginning (just after idlingspeed) is bad... then I`ll need to change my jets!

Anyway IÃ‚Â´m about to take the carburettor out and clean.... and try to inspect it...how and which way is the easiest to take it out... do I need to remove other stuff (more than the obvious stuff like sadle, tank ...)

well how do you do it?

/RIkard

What does the idlescrew and airmixturescrew do?

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