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NEEDLE UP OR DOWN .
#817658 07/27/20 4:43 pm
Joined: Sep 2016
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I have a new GP3 fitted to my DB500 it runs ok on the bench , even ticks over a bit , but when out on the road theres a definite stutter at about 3.5k revs . If I close the air lever it is better so i feel that the needle should be lifted slightly i have a 350 main jet fitted . . At the moment its in the centre of 5 notches . So before I trial and error does this sound like the right way to go . I also had a problem with the remote float flooding but I think ive sorted that .It is fine till start up then it starts to flood its a matchbox remote with new rubber fitting ive honed the float needle with autosolvo and it seems to be better .

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Re: NEEDLE UP OR DOWN .
ducati2242 #817679 07/27/20 9:35 pm
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Originally Posted by ducati2242
I have a new GP3 fitted to my DB500 it runs ok on the bench , even ticks over a bit , but when out on the road theres a definite stutter at about 3.5k revs . If I close the air lever it is better so i feel that the needle should be lifted slightly i have a 350 main jet fitted . . At the moment its in the centre of 5 notches . So before I trial and error does this sound like the right way to go .
If you close the air lever it makes the mixture stronger, which lifting the needle also does (at least, in mid-range). So, you'd want to drop the needle, not lift it. However, needles came in two varieties to deal with that problem when running a megaphone. What exhaust system do you have, and which of the two needles is in your GP?

Re: NEEDLE UP OR DOWN .
ducati2242 #817751 07/28/20 8:34 am
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If richening it using the lever improves it, surely you’d raise the needle as the OP suggests?
Is this a difference in terms ? Raising the clip/raising the needle being opposites ?

Re: NEEDLE UP OR DOWN .
ducati2242 #817769 07/28/20 2:09 pm
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The needle I have is 3GP6 [ p. no.316/408 ] and there is very little taper on it I think I may need to replace it with a 3GP [ p. no.316/465 ] the slide is a no. 4 . So I will buy a new one and report back when I have that one fitted it says in the book that the 3GP6 is the week needle .

Re: NEEDLE UP OR DOWN .
dave thomas #817779 07/28/20 3:12 pm
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Originally Posted by dave thomas
If richening it using the lever improves it, surely you’d raise the needle as the OP suggests?
Right you are. That said, in the case of the GP, depending on the exhaust system the mid-range behavior often only can be tamed by swapping the needle.

Re: NEEDLE UP OR DOWN .
ducati2242 #817791 07/28/20 4:46 pm
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It has a street exhaust although it is a stainless steel one . The front pipe is the normal chrome item .

Re: NEEDLE UP OR DOWN .
ducati2242 #818163 07/31/20 11:24 am
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My new needle has arrived . Cant try it for a week though as im not at home but will get round to it . For those that are interested heres a photo to show the difference between the 3GP6 and the 3GP . You can see the difference in the taper .

[Linked Image from i.ibb.co]

Re: NEEDLE UP OR DOWN .
ducati2242 #818278 08/01/20 8:22 am
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Legend had it that if you could get the bike to run on the 3GP6 (effectively the megaphone option as noted above) needle it would be better.

I tried the 3GP6 on my street DBD and it was not a success, though some time fooling about with needle jets and pilot jets might have improved it. It was simpler and quicker to go back to the 3GP needle with the street exhaust, on which the bike ran fine.


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes

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