20 pilot on stock 2006 F

[rkjjeep]

I installed a 20 pilot on a bike with stock intake and exhaust.  I talked about that in another thread but thought it best to post my results here. 

At first I thought it might be too much pilot jet.  I pulled my Ganson gastester out of the closet and calibrated it for 2% CO in ambient air.  A rule of thumb CO level at idle is 2% to 4%.  Specific bikes will idle best somewhere in between but the general guideline is if you can't get it between 2 and 4 you have too little or too much jet.  OBVIOUSLY everything else has to be spot on before checking this.

I had set the mixture screws at 2.5 out after installing the 20 pilots.  That resulted in over 4% CO so I started backing them down 1/16 turn at a time.  I settled on 1.5 turns out.  That gave about 3.2% CO, nice stable idle set at 1100, and really nice just off idle feel and response.  I'll leave the 20's in and ride it for a while.

Bottom line - the 20 is ALMOST too much pilot for stock intake and exhaust based on sample of ONE bike CO measurement.  If you use the 20 pilot 1.5 turns might be a good starting point.

If you are curious about the CO meter (and they used to be MUCH less expensive)!:

http://www.autoexpertproducts.com/gastester.htm

[Suzuki Stevo]

#20 pilots and one size up on the mains, was the first mod I did to my bone stock 07'. All carburated on road bikes shipped into the USA have been lean since the 70's...maybe longer? 

[rkjjeep]

The manufacturers do what they have to do to meet the tailpipe emission standards as the bike is driven on a "hiway" and "city" cycles on a dynamometer.  Yes, most bikes run "lean" as compared to best mixture for driveability for quite a few years back.  Fuel injection helps avoid the compromises but the new standards still make it tough to make a bike run sweet.  Makes it fun for us, though!!

[narftroz]

Say i just got a new bike(new to me) an 04 gsf and I just ran it through an emissions test, which is required by the state here, and its CO% was .38, that seems a little lean to me? The maximum standard for the state is 5.5%. I don't know if it helps but my HC in ppm was 191 and the standard is 1800.
so should I aim for fatter jets? and if so what size do you recommend?
Thanks
T

[rkjjeep]

I'm not the expert but most engine idle best between 2% and 4% CO.  0.38 is pretty lean. 

[The Buddha]

Humidity and air temp play a part too, but dry warm weather = 20 is a shade over kill ... I'd like a 19 ... or 18.5 ideally.
A 2.5 step up in 17.5 is huge, over 20% but 2.5 in 130 is under 1.5%. Weird, but in the absence of a 19 I'd try a 20 ...

BTW 83-84 was the last year afaik stock bikes were jetted OK from the factory. That is based on my xs650, nighthawk and kz440's.


Cool.
Buddha.

[rkjjeep]

I think Buddha is right on the money.  The CO test does show that the 20 is not WAY out of range - you can make it work.  You'll either have the 17.5 with mixture screw almost off the spring or you'll have the 20 with the screw turned in some.  Maybe if that 20 gets just a LITTLE dirty...............

[The Buddha]

In that pilot jet range the sizes oughta go every 1 atleast ... like 17, 18, 19, 20 etc. Get closer to 50 and you can do 1.25, and past 100 you can go 2.5. That 2.5 all the way to 0 ... well duh, its a bad idea. The savage guys do something like run a #77 drilled jet in the stock whatever they got ... puts the 50 into like a 51.5 if I remember, or the 47.5 into a 48.5 ... I dunno whatever that #77 is.
Well too bad there aint no numbered drill down to the 2/10th of mm the 20 is ... and even so we need like 1.9/10th ...
Cool.
Buddha.