Tuning the Dell Orto Carb on a 650

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Joined
Nov 20, 2001
Messages
17,023
Location
Ely, England
Hey up!

Just to let you all know that I'm in the slow long slog of tuning the standard 40mm carb on the 650 2002 model I have here.

as many of you will have seen on my Facebook page, we had the NTB650 starting with virtually no choke. if this can be cured it will but it will come last.

the first task is to jet the bike as well as I can on the minimum of replacement parts. after that, I will keep quiet on a code or two in order to protect my business interests and reward me a little for my efforts.

So the tune of the NTB is: standard other than
dished piston, narrow squish. piston 3mm taller than original at rim
DVSK
Iridium IXU24 plug
flowed 37mm inlets
08 cam
ignition advance set at 6d as per videos on Taffmeisters

gearing is 16/40. the bike pulls 6th nicely to the rev limit.

standard jetting in europe on the quality fuel (sorry USA!!!) is found in the manuals for 2001-2003 and is
190MJ
DR272 atomiser
40 slide
40PJ I think
clip 3 (C3)
size of the Pilot air entry is 1.0mm
size of the main air entry is 1.5mm
fuel screw should be 1.5 turns out.

the first thing you need to do with the standard jetting with the 08 cam fitted, is to drop the needle to clip 1. this stops a low speed 'chugging'.

we have the choke mounted on the handlebars (we sell a choke cable for this both up to 2000 with a perch and 2001-2003 on the magura clutch lever).

very little choke is needed. 1mm? maybe 2mm tops?

we presently sell a larger slide cutaway and larger PJ which helps electric start and makes the difference. the kickstarters seem to drive through so hard the bikes start easily enough. but the K/S have a dry spot with the original /40 slide just off idle. you open the throttle and there's a judder and a noise through the carb that just shouts "I'M THIRSTY".

the spruce up kit is therefore better even on the kickstart model IF you're looking for subtle throttle movements. this goes for all Husabergs of the PHM dell orto carb period.

so that brings us up to date with starting the bikes. most of you who are interested, have visited Facebook/Taffmeisters/videos and seen this.

my work now is going to be based on TUNING the carb to the best state I can purely using 'seat-of-the-pants' testing.

I also have the advantage of a dell orto needle comparison data graph so that I can compare the needle profiles and I hope that it is good. I'm not sure....I know the profile of the needles but not the scale of change in the fuel graph. i also don't know the fuel curve because there is no input for the PJ at all.

there are two types of needle eligible for the PHM carb and they are the K-series and the U-series. the U series are 6mm shorter but seem to end up being usable.

at WOT there is only 6mm of needle left in the DR atomisers so clearly it is NOT with these atomisers that we use that the U-series have been designed for!

regards

Taffy
 

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