While I have the bike apart, I'm rebuilding the carb. Carb is stock. Bought the bike with White Brothers E-Series 2into1 pipes and stock air cleaner with a K&N element. The carb has seemed like it was set up well although the float was either off or leaking as setting the bike on the side stand while running would case the idle to come way down and sometimes stall (as if it was flooding) and sometimes if leaving the petcock opened while parked I would get gas on the floor. Gas mileage has never been as high as I thought it should be but wasn't terrible.

The manual says it comes with a 175 (or 160 California) main jet and a 42 slow. Upon opening the carb, the main is a 160 and the slow is a 20? I don't think the bike is from California as I bought it in Ohio. The idle mixture screw was one full turn out and throttle response was always good.

I never heard of a 20 slow jet. Usually I run across slow jets in the low 40's and after a stage one, they wind up around a 46 or so.

Anyone ever heard of a 20 slow jet and why it would be used?

Edit:I should probably mention that the needle jet is adjustable with 6 clip positions. The c-clip is in the third from the top and there are three washers on top

 

20 is very small jet. Never seen one of this size. But if Your bike runs well then why change it? Is it overheating? But on the other hand, your settings are wierd - one turn on mixture, 20 slow jet with aftermarket pipes and K&N... Wierd.

I looked up FLH/FLT/FXR manual and the smallest slow jet on these models 1984-98 is #40 which I`m running on my totally stock EVO. Sizes will be similar on Softails.


Washers ABOVE the needle c-clip are holding the needle in place. Without them the needle would move up and down a bit.

 

You sure its not a 50 and you are just reading it wrong?

 

I think you may be reading something wrong. Did you by chance pull the needle jet out? I don't know if they have numbers on them or not but maybe you are reading that.

 

Nope. It's definitely the slow jet and it definitely stamped with a 20. If the 2 was a 5, then it would read as an 05, not a 50. I've rebuilt many carbs, installed Dynojet kits, Youst kits and I keep an inventory of new main jets 160 to 200 in tens and some fives and slow jets in twos through the 40's so I know which jet is which. If I had to guess, the needle looks like it's from a Youst kit, but some of the tapers are pretty close so that may not be correct. The needle jet or jet holder or tube depending on what you like to call it looks to be stock as it only has two holes, one on each side. There are no markings on it.

I Googled Harley "slow jet" 20 and found a few posts (including this one) with people running 20's but not a whole lot of detail. Any other ideas?

 

Could it be that it was drilled out? I have done that before, instead of buying a new one. I didn't restamp it either.

 

OK, I may have figured something out. I went through my box of pilot jets and just found out the largest I have is a #46. I gotta stop giving them away. Time to order some more. Anyway, holding the #20 and the #45 together and looking through them with a magnifying glass, the #20 is quite larger than the #45. The #20 is still larger than the #46, but not by a lot. Looking all over trying to find what the equivalent sizes are, I couldn't find anything on pilot jets but I did find a table for Kiehin main jets. A 0.020" main jet is a #55. The jet numbers are just a chart lookup and not a mathematical size chart. Now it doesn't look like the #20 pilot jet is a #55, but if Keihin's pilot jet numbers are near but different than the mains, then maybe this is some aftermarket jet where the #20 stands for 0.020 inches?

Or maybe it's just been drilled out as Jim said. They thing is, I cannot find a listing for a #20 Kiehin pilot jet anywhere on the Internet that is for the Kiehin carburetor in a Harley.

Anyway, the long of the short is that if I had to guess, the hole in the jet looks to be in the range of somewhere around a #48 which would be close to where I would think the carb might need to be tuned. Guestimating, I would think this would be just a little rich which would explain my perception of slightly poorer gas mileage than I would expect.

Now I'm trying to decide if I wanna put the carb on with the #46 and try it out or use the mystery #20 and wait until I get a #47 and #48 back in stock. I'm thinking #46 might be a bit lean.

EDIT: Hrmm. Just read an article from Joe Minton (who knows a little bit about CV carbs). He states that the pilot jet number is actually in 1000's of mm. Therefore a #42 slow jet is .0042mm and my mystery #20 probably started life as a .0020mm and was drilled out by someone. I wonder where they got a #20 from in the first place.

 

If I were you I would put the 46 in and turn the mix screw out 2 1/4-1/2 turns and put the 170 main. Leave the 3 from the top needle.
Now, like someone said, ....if it runs okay, leave it alone!
However, I know, you're after fuel mileage, so just try it, you can always go back. I believe you were getting away with 1 turn out because of the big mid jet w/stock motor.
my 2 cents carb advise

 

I run a 48 low with a 195 main, a spacer under the stock needle and a high flow air filter with a totally stock motor except for an EV27 Cam and a Boyesen Twin Shot float bowl.

The bike was a fresh import from California...I have no idea how it even ran with the jets it came with...your gas must be a way different mix from ours!