A/f screw
Hell everyone I am a little over my head on this so here I go I have a 01 Fxd it runs good but my plugs are black I know that means that its running rich so do I turn that a/f screw in or out? Or do I get new jets? When I get on the throttle it goes no bogging down or anything my friends tell me too just leave well enough alone? Thanks for the help in advanced. What is the stock setting on the screw?
http://www.harley-performance.com/ha...r-jetting.html
https://www.hdforums.com/forum/dyna-...ng-a-carb.html
https://www.hdforums.com/forum/fuel-...retor-pic.html
https://www.hdforums.com/forum/fuel-...ggestions.html
http://www.harley-performance.com/ha...arburetor.html
https://www.hdforums.com/forum/fuel-carb-related-60/
LOSER
Joined: May 2010
Posts: 5,719
Likes: 4
From: Williamston, NC
Never done a carb rejet by myself; got some interesting links for you, though:
http://www.harley-performance.com/ha...r-jetting.html
https://www.hdforums.com/forum/dyna-...ng-a-carb.html
https://www.hdforums.com/forum/fuel-...retor-pic.html
https://www.hdforums.com/forum/fuel-...ggestions.html
http://www.harley-performance.com/ha...arburetor.html
https://www.hdforums.com/forum/fuel-carb-related-60/
http://www.harley-performance.com/ha...r-jetting.html
https://www.hdforums.com/forum/dyna-...ng-a-carb.html
https://www.hdforums.com/forum/fuel-...retor-pic.html
https://www.hdforums.com/forum/fuel-...ggestions.html
http://www.harley-performance.com/ha...arburetor.html
https://www.hdforums.com/forum/fuel-carb-related-60/
Supporter
Joined: Jan 2007
Posts: 15,788
Likes: 5,625
From: along the shore of Mishigami
If you can see the A/F screw under the backside of the carb, then I would venture to say the carb may have been "worked on". The stock jets are 45 and 190. The a/f turns ,out from lightly seated, are about 1 1/2 to 2. I'd start at 1 1/2 and if you have carb "pops" (farts) then turn the screw out about 1/8 of a turn. A carb fart is a result of a lean mix. The slow jet (45) is used to almost 3/4 throttle. By the way, idle should be at 1000 give or take 50 rpm, this is for a couple of reasons 1) maintain oil pressure at idle 2) maintain a charge rate of 13.2-13.4 volts, the charging system is a bit anemic on the carb bikes at idle.
Tourer
Joined: Nov 2011
Posts: 421
Likes: 4
From: Alabama
If you can see the A/F screw under the backside of the carb, then I would venture to say the carb may have been "worked on". The stock jets are 45 and 190. The a/f turns ,out from lightly seated, are about 1 1/2 to 2. I'd start at 1 1/2 and if you have carb "pops" (farts) then turn the screw out about 1/8 of a turn. A carb fart is a result of a lean mix. The slow jet (45) is used to almost 3/4 throttle. By the way, idle should be at 1000 give or take 50 rpm, this is for a couple of reasons 1) maintain oil pressure at idle 2) maintain a charge rate of 13.2-13.4 volts, the charging system is a bit anemic on the carb bikes at idle.
Good advice.I can tell you this about my TC88. It was completely stock when I got it (45 slow jet/190 main installed, OEM AC & exhaust) and when temp was below 55 or so, it had a really bad miss at part throttle, and it backfired pretty badly when throttle was chopped. Plugs powdery white. Clearly too lean. After a LOT of experimentation, I found it had to have at least a 48 slow jet (50 better) to get rid of the part-throttle miss/backfire, but the 190 main was fine as long as two #4 washers were installed underneath the stock needle. I think most would say a 50 slow is way too rich for stock TC88, but works for me in winter. I expect I'll have to drop back to a 46 slow when hot weather hits. It just is what it is. Just my experience with an old TC88 (45K mi).
Cruiser
Joined: May 2011
Posts: 207
Likes: 0
From: durham
Not sure why he would tell you that, i have an 02 and always pull the choke out and let her warm up a bit and then push back in. Pumping that throttle like that usually will flood it, i think if it is below 30* that they suggest you pump the throttle once
Cruiser
Joined: Oct 2010
Posts: 101
Likes: 1
One thing to always do with adjustable jets is to carefully count and measure your turns and direction of movement from start. A stubby pencil beats a long memory every time. At least you can get back to the start point that way. In the wind.
Pops
Pops
Supporter
Joined: Jan 2007
Posts: 15,788
Likes: 5,625
From: along the shore of Mishigami
Thankyou for the correction there Foxster, "the idle air mixture screw". Because of the taper on the main jet needle the fuel is controlled primarily thru the slow jet and the main jet comes in after about 3/4 or more throttle. That is mainly the case on street bikes. Some folks even change the needle to a Sportster (circa 1988) to help the transition from idle into the acceleration mode, if the acceleration pump isn't in play. Just trying to help some one out. Again thanks for the correction.
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Outstanding HDF Member
Joined: Nov 2010
Posts: 2,250
Likes: 36
From: Montana
An easy way to adjust the AF mix for the idle circuit of the carb is to (after the bike is warm) turn the air bleed screw in until the bike just about quits then turn it out (counter clock wise if I m not mistaken on a cv carb) until it stumbles and either just about dies or spits black smoke. Then go in halfway between the two and that is where it should run the best . Might need a very slight tweek one way or the other after but that is where your base line adj. will be. BTW on a stock carb the air bleed screw is covered by a very thin metal cover. As it comes from the factory you cant adjust this. Every CV carb owner I have ever known had the HD dealer drill out the metal cover so the screw is then adjustable or if you get an aftermarket jet kit ie. dyna jet kit or keihin etc. there is usually directions on how to do this yourself. Its not too difficult but you must be careful not to drill in too far. If you have any doubts you can do it yourself , any good shop can do this in about 5 minutes.
Last edited by missedem; Jan 21, 2012 at 09:56 PM.
Outstanding HDF Member
Joined: Nov 2010
Posts: 2,250
Likes: 36
From: Montana
if the bike does not run smoothly after doing this you might need a carb adjustment of some kind . Either a different jet or jet needle setting. There are all kinds of jet kits on the market for this . Keihin makes one, dyna jet makes one. They are all over the place and they virtually all work the same. Good luck and sorry if I got long winded.