A few questions about my carb - Harley Davidson Forums: Harley Davidson Motorcycle Forum
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Old 12-29-2010, 11:14 PM   #1 (permalink)
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A few questions about my carb

ok so i have been having problems with the bike being lean between 3000 and 4500 rpm's 01 dyna 95 ci
i have the SE 44mm CV carb on there with the stock needle no shims and a 250 main jet unsure of the pilot jet size.
the A/F needle that i hear about if i adjust that it only affects lower rpm's correct? because i am good in the low's as far as A/F ratio.
the vacuum slide on the carb i know it moves as i give the bike more throttle, but if i am cruzing at 4000 rpm's at only 1/4 to 1/2 throttle is it wide open or only part? i know that when i snap it to full throttle it goes all the way open but that is only for like a rev or quick burst.
Because i figure that if it is only supposed to be part open then i need to move the needle up with a shim.
Now I have no problem getting around the bike has power and when i get on it it feels fine. and when i am stopped and give it a rev it is there instantly no lag or nothing and i don't remember any sounds like pops or crackles except when i was cruzing at 60 mph in 3rd gear at 4100 rpm's and i rolled off the gas for a bit and on the way down it popped a small bit but i think that is normal.
Another question this all started happening after a new cam install. i changed from a se s203 to a se s257 can the cam somehow be causing my lean problem that is am just unaware of?
thanks for any help.
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Old 12-30-2010, 02:33 AM   #2 (permalink)
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Need to find out what size the pilot jet is. How many turns out are you on the F/A mix screw? While it souds like the slide vac. diaphragm is working ok, it would be good to double check it for proper sealing to ensure it's functioning properly. The main jet sounds way fat for a 95" motor with the cams you're running. And finally, I believe the majority of your problem is with the needle being too lean causing problems in the mid rpm range of operation. Either shimming to raise the needle and richen the mid-range mixture is needed or a whole new needle that would richen the mid-range up.

Too bad you're not local to me as I'm confident I could tune it for the best condition for the 95" application for right around $60.00.

You'd pull it out of the box, bolt it on, adjust the F/A scew 1/4 - 1/2 turn and set the idle speed and ride away trouble free.
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Old 12-30-2010, 07:01 AM   #3 (permalink)
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Hey Spoon I'm thinking your main jet is to large , I'd back it down to a 195 . 3000 - 4500 rpm is the transition range between the intermediate and main circuits . The 44mm carb moves air thru the venturi slower than the stock carb does so there's less vacuum to draw fuel up thru the needle jet . The smaller hole in the 195 jet will allow the vacuum thru the venturi to more easily draw fuel up into the air stream .
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Old 12-30-2010, 07:26 AM   #4 (permalink)
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Quote:
Originally Posted by Airborne Spoon View Post
ok so i have been having problems with the bike being lean between 3000 and 4500 rpm's 01 dyna 95 ci
i have the SE 44mm CV carb on there with the stock needle no shims and a 250 main jet unsure of the pilot jet size.
Agreed. Main jet is way to large. Go to a .195 or .200 tops.

As well, shim the needle jet, to eliminate lag during progression. (.050" shim to start)

Pilot jet is only for idle and low end throttle movements.

What people fail to realize is that, HD is under EPA stringency for emissions for idle and midrange rpms. The pilot jet and a/f screw settings will be lean from the factory.

NO company is monitored for WOT emission, therefore, main jet settings are pretty close to what you need, and fat, regardless of other settings.

Unless you replace cams, (like in your case) or something requiring more fuel, generally, the main jet in most carbed bikes is right on the money, or you'll only need to go one size larger.
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Old 12-30-2010, 07:30 AM   #5 (permalink)
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.050" shim , really ? That's wider than a spark plug gap !
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Old 12-30-2010, 07:33 AM   #6 (permalink)
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Check out Thunderjet.the web site will tell whats its all about. With it on my carb {super E} it flat lined the air/fuel mix.
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Old 12-30-2010, 07:34 AM   #7 (permalink)
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Quote:
Originally Posted by SCHMIDTYS View Post
.050" shim , really ? That's wider than a spark plug gap !

.50mm shim. Not inches.

Or.....27094-88 Main needle ('88 XLH part)
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Old 12-30-2010, 07:39 AM   #8 (permalink)
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.50mm shim. Not inches.

Or.....27094-88 Main needle ('88 XLH part)
Gotcha ...
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Old 12-30-2010, 01:37 PM   #9 (permalink)
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ok i am gonna head down to my harley shop and get a new 195 main jet. and i will grab a new needle if they have one otherwise i will just shim it. where can i grab some shims that size? napa, kragen or someplace else?
my a/f screw is stock it hasen't been moved because the cover is still on it. will adjusting that change anything in the upper rpm range?
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Old 12-30-2010, 02:13 PM   #10 (permalink)
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So I was mistaken my a/f screw was set at 3 1/2 turns out. Also my pilot jet is a 48.
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