CV 40 Pilot Jet

[forgetaboutit]

2000 Dyna TC88. Andrews 21, Supertrap 2 into 1 w/ 17 disks. Vented to atmosphere. Stock CV 40 (27421-99c) with Sportster needle (27094-88) and 2 #4 washers. Recently installed 06 Heads and then went from 14 to 17 disks.

Now getting carb farts and pop on decel. Went to 3 ¼ turns out and most of it is gone. I think I need to up a size or two with the pilot jet.

Currently a 45 and I assume the proper way is to go up one size at a time. I see they make a 46 but I will probably end up at 48, I have not seen a 47 anywhere.

What do those in the know think and should I just start with a 48?

[rigidthumper]

I would order a 48 (27165-90) and evaluate- mileage will decrease slightly with the 48, but I like the better mid range manners.

[Billy]

Yeah, try a 48 pilot and pull a washer from under the needle

[smoserx1]

Yes, try a 48, but that setup you have now sounds awfully rich to me.  A Sportster needle and washers both?  Anyway I had these issues when I installed SE203 cams in my 99 FLHT.  I had to go Sportster needle, 48 pilot and stock mufflers to get rid of the issues.  But when I went to Andrews 21N cams all that changed.  I was able to reinstall my screaming eagle mufflers (old loud ones), go back to a 45 slow jet, and set the mixture to only 1.5 turns out.  And  since then I even got rid of the Sportster needle and went with a NOKK which is a tad leaner.  I picked up a couple of MPG just by doing that.  Back when I had the 203s and the 48 I was always smelling gas fumes...I guess every setup is different.  If the 48 is too rich try a 46 but remember the 46 is not a Keihin product so the H-D dealer may not carry it.  Good luck.

[Hillside Motorcycle]

And do not rule out a 50, and btw, doubt that is enough discs also.

[dogger]

Check for vacuum leaks at the manifold as well. After installing 06 heads on mine, I had to do a little work on the manifold to get rid of a leak that made it difficult jet correctly. Now with an NOKK needle and a#45 jet, it seems to be running just fine.

[forgetaboutit]

As always, thanks for all the responses.

I removed the two washers, left in the Sporster needle and did a 48 Jet. (It was the only one I could find locally). Settled in the air mix at 2 turns.

Put about 100 miles on today. Bike runs great, no pops, no coughs and comes back to idel nice and smooth even after extended high speed runs. Prior to the jet change I was getting "idle creep" by a few hundred RPMs after high speed running.

Haven't needed to get gas yet so I haven't checked millage (range).

Doggger, prior to jetting, I did check for leaks, none found. Did you know the intake flange for 06 heads is different. The P/N for the new style flange is 26993-06, (2) required.

Hillside, two questions. 1) What do you estimate the disk count should be? 2) Because I am running good, what benefit, if any, would going to a 50 bring.

Again, appreciate the help.

[Hillside Motorcycle]

I'd suggest 24-30 discs from what traditional/historical info we have gathered from the use of those on the dyno.

[forgetaboutit]

Thanks Hillside. I am a little surprised by your reply but am still learning. I guess I was always afraid they would be "too open".  I'll play around some more and see how it goes. I'll come back and let everyone know in a few days/weeks. Getting some cold weather here in Chicago, my personal riding temp low is about 45 degrees so I can get out today but then may take a few days off.

[forgetaboutit]

Summary:

Hillside, (the oracle of knowledge), you were spot on, thanks for jumping in on my thread. I started off with 29 disks, that is all I had. It was a little too much, became a little too lean and had some coughs. I worked down to 24 at 2 2/8 turns and she is running great. That is about all I can wring out of the 48 jet. It seems the power band moved up a few hundred RPM, that is ok.

Now I see why I may need to go to 50. Previous with the Supertrap, I always started out with a low disk count and moved up. Now I realize starting with everything on and working down is the better way. It is near end of season so if I decide to go back in to the carb it won't be until next spring. However, the bike is very well behaved and runs better than ever now. I may just be done.

Rigidthumper, Billy and Smoresex1, I learned something else. If I hadn't put on the 06 heads, thereby increasing the flow, I never would have seen the need to rejet. Having the Sportster needle AND washers and being 3 ½ turns out caused the idle circuit to be too rich, hence the "idle drift" after hard running. It would creep up from 1000 to about 1200/1250. Not terrible but a tad faster than I like. Slowing down and driving "normal" it would gradually return to 1000ish. I searched several times but never found a correct solution so I just lived with it. Getting rid of one or the other (I pulled the washers) coupled with proper jetting to get back to the 2 to 2 ½ turn range on the air mix seems to be the answer, at least for my build. Now, no matter how I ride, when I come to a stop it idles at 1000.

Carb and pipe tuning is half art and half science. You can look up the science part in a book but learning the art part is difficult, particularly for those of us who only have one bike at a time. Therefore I'll say again, I very much appreciate the knowledge and assistance.

[forgetaboutit]

Adding one more thing about the Supertrap – another benefit to adding disks is it gets louder. These pipes are a little quieter than I prefer but the tunability is worth the compromise. They are louder than stock but would prefer to make a little more noise.