HELP !!! Need jetting info
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Road Captain
Joined: Oct 2007
Posts: 516
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From: Ontario, Canada home of the TAX YOU TO DEATH LIBERALS
HELP !!! Need jetting info
Just changed the carb on my stock 84 EVO 1340. \\; Put on a CV from a 99 Road King. \\; It starts and idles fine but bucks ,spits and backfires upon acceleration. \\; Current jets in carb read 45 &\\; 75. \\; I think they are rich for the little 80 EVO as I believe this carb came off a 88. \\; Anybody have any thoughts? \\; Thanks
Road Master
Joined: May 2007
Posts: 794
Likes: 3
From:
RE: HELP !!! Need jetting info
Well, those are the jets in my '96 Evo, and it runs fine (175 main). I do have aftermarket pipes and high flo air cleaner though. Did you make sure all the pasages were clean, and the diaphram had no holes or is pinched, before you installed it?
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Cheers... Ben.
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Cheers... Ben.
HDF Community Team
Joined: Dec 2005
Posts: 5,374
Likes: 2,570
From: NC USA
RE: HELP !!! Need jetting info
You're not rich - you're LEAN on the idle mixture.
 \\;
I did a similar swap with my basically stock '87. You're close on the jets. 48 / 175 in mine and I get 50+ mpg knocking around under 60 mph and 44 - 48 interstate mileage.
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Bear in mind, that if it's doing what you describe \\;AFTER it's warmed up, you likely have a leaking intake seal(s) Did you install new ones?
 \\;
First, you gotta take it off and drill out the soft plug that covers the idle mixture screw. (It's located in the main body, bottom - center at the \\;edge of the bowl on the intake side) Drill out the plug, then turn the screw IN all the way (gently) then back it out about 2 1/4 turns to get close. That will effectively cure your spitting and coughing.
 \\;
I have a lot of hours in, learning how to tune mine \\;for economy and performance. Lots will tell you all kinds of "tricks" but if you're looking for longevity, dependability and decent mileage, stay in touch.
 \\;
\\
 \\;
 \\;
I did a similar swap with my basically stock '87. You're close on the jets. 48 / 175 in mine and I get 50+ mpg knocking around under 60 mph and 44 - 48 interstate mileage.
 \\;
Bear in mind, that if it's doing what you describe \\;AFTER it's warmed up, you likely have a leaking intake seal(s) Did you install new ones?
 \\;
First, you gotta take it off and drill out the soft plug that covers the idle mixture screw. (It's located in the main body, bottom - center at the \\;edge of the bowl on the intake side) Drill out the plug, then turn the screw IN all the way (gently) then back it out about 2 1/4 turns to get close. That will effectively cure your spitting and coughing.
 \\;
I have a lot of hours in, learning how to tune mine \\;for economy and performance. Lots will tell you all kinds of "tricks" but if you're looking for longevity, dependability and decent mileage, stay in touch.
 \\;
\\
 \\;
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Road Captain
Joined: Oct 2007
Posts: 516
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From: Ontario, Canada home of the TAX YOU TO DEATH LIBERALS
RE: HELP !!! Need jetting info
Had changed the manifold over to newer style (replaced the rubber boots). \\; Checked for leaks via the WD 40 spray test, and it never even sputtered. \\; Plug was already out of idle adjustment. \\; Same is set @ about 2 3/4 turns. \\; Idles good, starts right up. \\; When you roll the throttle slowly it revs fine when you roll the throttle harder she bucks, spits and backfires out both exhaust pipes. \\; As well, the plugs are pretty black from only a short run. \\; also checked the diaphram and spring and both look good. \\; inside of the carb was clean and made sure all passageways were clean and open. \\; It does push out a noticable spray out the front of the carb \\;when you roll the throttle.
Road Warrior
Joined: Dec 2007
Posts: 1,286
Likes: 64
From: SoCal
RE: HELP !!! Need jetting info
The fuel spraying backwards out the carb is due to a reversion wave. Try torque cones in your exhaust to stop the wave from interupting intake flow. I believe it is causing you to go lean during acceleration.
Intermediate
Joined: May 2008
Posts: 25
Likes: 0
RE: HELP !!! Need jetting info
Might want to put the 68n 88 1200 Sportster needle in or shim the stocker about .030-.050. Check all the other things mentioned also
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Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
RE: HELP !!! Need jetting info
If the carb was already drilled out somebody already had their hands in it. The most common problem we have found that causes your symptoms is the needle jet in upside down. If you look into the throat of your carb you will see a little silver piece that the needle goes into. It is held in place by the main jet holder. Take out the main jet holder and remove the needle jet, the end that goes up and the needle goes into has a slight taper on the inside of the hole the other end that goes against the main jet holder is flat. If your float level is OK then this is probably your problem. Hope this helps.
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