CV carb jetting
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,081
Likes: 2,159
From: Ohio
[QUOTE]
Mixture screw only controls up to around 1500 on a CV, you are on the needle in the range you are talking, shim the needle up or live with it if your wanting to squeeze mpg.
Mixture screw only controls up to around 1500 on a CV, you are on the needle in the range you are talking, shim the needle up or live with it if your wanting to squeeze mpg.
Thread Starter
|
Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
Thanks for the info.
Im not sure what the rpms are when she pops... Id guess Im right around that 1500 rpm range. Just loping along at an easy pace, close to that 1500 rpm, then roll on the throttle up to 2500 or so... it seems she pops late in the de-acceleration.... like when Im getting back closer to 1500 rpm.
Shim the needle up?
The needle had five notches... Its set in the middle.
Would I move the clip to the notch closer to the working end of the needle?
Im not sure what the rpms are when she pops... Id guess Im right around that 1500 rpm range. Just loping along at an easy pace, close to that 1500 rpm, then roll on the throttle up to 2500 or so... it seems she pops late in the de-acceleration.... like when Im getting back closer to 1500 rpm.
Shim the needle up?
The needle had five notches... Its set in the middle.
Would I move the clip to the notch closer to the working end of the needle?
Advanced
Joined: Jul 2018
Posts: 90
Likes: 62
From: USA
97 FLHR: kerker slip on mufflers with stock headers, Screaming Eagle air cleaner, Screaming Eagle ignition, EV13 cam.
My gas mileage has deteriorated bit by bit through the last 3000 miles or so, and I recently noticed a sluggishness with throttle response and overall performance. (Felt very rich and the plugs were a bit sooty at the base of the ground prong, mufflers a bit sooty, and started getting backfires on de-acceleration)
In checking things I uncovered intake leaks at all three seals. The diaphragm had a hole, and the slide needle clip had come off.
I took the carb to a local Indy to install a V-Twin carb kit. He says he set the needle and mix screw to midpoint.
This carb had been re-jetted in 97 when the bike was new and has always performed nicely. I vaguely remember the slide spring being changed to a lighter version at the time. I thought the diaphragm material seemed thinner than what came in the kit too.
The jet sizes seem a bit weird; 45 and 150.
I havent reinstalled the carb yet, but just wondering if I should change out that main jet before reinstalling the carb. Im not sure which spring he reinstalled or if there is a difference.
Any input from you tuners is appreciated.
Oh yeah, Im not drilling a hole in my pipe for an AFR... lol
My gas mileage has deteriorated bit by bit through the last 3000 miles or so, and I recently noticed a sluggishness with throttle response and overall performance. (Felt very rich and the plugs were a bit sooty at the base of the ground prong, mufflers a bit sooty, and started getting backfires on de-acceleration)
In checking things I uncovered intake leaks at all three seals. The diaphragm had a hole, and the slide needle clip had come off.
I took the carb to a local Indy to install a V-Twin carb kit. He says he set the needle and mix screw to midpoint.
This carb had been re-jetted in 97 when the bike was new and has always performed nicely. I vaguely remember the slide spring being changed to a lighter version at the time. I thought the diaphragm material seemed thinner than what came in the kit too.
The jet sizes seem a bit weird; 45 and 150.
I havent reinstalled the carb yet, but just wondering if I should change out that main jet before reinstalling the carb. Im not sure which spring he reinstalled or if there is a difference.
Any input from you tuners is appreciated.
Oh yeah, Im not drilling a hole in my pipe for an AFR... lol
Grand HDF Member
Joined: Nov 2009
Posts: 4,315
Likes: 1,663
From: Tampa
While the idle mixture screw is commonly only under operation until just off idle to 1/8 throttle, RPM is not as relevant to when that fuel passage is in play. For instance, if you're doing a dyno pull and slam the throttle closed even though the engine is spinning down from 6000 rpm you bet your *** the idle mixture passage is dumping 100% of its fuel because the throttle is closed and the bike is still running.
Sweet spot is 3 turns out on the idle mixture screw at anything less than 2000' elevation. Have you removed the plug from where the idle mixture screw is located?
Sweet spot is 3 turns out on the idle mixture screw at anything less than 2000' elevation. Have you removed the plug from where the idle mixture screw is located?
Road Warrior
Joined: Dec 2017
Posts: 1,503
Likes: 2,854
From: Delaware
Gogobeck, Ive got a similar set up as you, '98 Evo Dyna, SE slip on's with stock headers, Big Sucker intake, Dyna 2000i ignition and EV13 cam. I bought an already modded carb, came with a 48 pilot jet and a 195 main jet, lighter spring and a drilled slide. Thoes jets were way too rich. Ive since backed them down to a 45 pilot and a 185 main and could possibly come down to a 180 main jet. This winter Im going to return to a stock non-drilled slide. Before all these mods I got a steady 48-50mpg. After engine mods (cam, ignition, etc) and extra rich jets I dropped to about 32 mpg. Since backing down to 45/185 jets, Im at about 40 mpg. I get my CV carb parts and jets from CV Performance, never had a problem with their stuff.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,081
Likes: 2,159
From: Ohio
You are not too rich or the exhaust wouldn't be gurgling or popping which is present right now, a 45 and 185 works well in a early intake timing cam bump like a EV13 . If the slight gurgle doesn't phase you then leave it alone, if it bothers then you know what rpm's the exhaust pop is coming in so you know what circuit is lean. Since you don't have a spot on rpm the pop occurs, making changes needs to have more information, wouldn't touch nothing until you ride it for a while and pin point the problem area.
Many of us tune with equipment and not just guessing, I've road many miles with a Wego live on a modded CV, Mikuni 45 and a R1/Super G, carbs are more of a controlled drip and we seem to over think them thinking the dinosaur technology is a precision measuring devise and learn a lesson.
On your needle question, raising the needle would require lowering the clip, if your taper is aggressive on the needle it may make your situation too rich or maybe just right, you never know, the center notch is a starting point but they make different tapered needles. The needle controls your cruising range afr's and affects mpg so it is a fine line, run my engines rich and not worried about fuel mileage, saving dimes can cost a engine plus you won't have a shotgun go off in the exhaust pipe. Leave it alone and RIDE the bike.
Last edited by 1997bagger; Sep 9, 2018 at 05:38 PM.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Thread Starter
|
Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
Ive been running up and down the same 5 Miles of road in the misting rain all afternoon... I think the cows have had about enough of me.
The bike starts easily, idles nice and runs great at anything over that 1/8 throttle. No pops on de-acceleration.
At any speed, when just barely on the throttle, it is not smooth, a bit jerky... I can tell when she moves to the high circuit. Ive adjusted the low speed mix screw in 1/8 increments clockwise until almost seated and counterclockwise until its almost falling out. In the middle about 2 1/2 - 2 3/4 turns out from seated, is best, but still not smooth.
I was originally concerned about the 150 main, but I understand that to be an air jet and only really in play when the slide moves up... is that right?
I called the guy that tuned this carb 22 years ago;
He says what he did was change the jets and enlarged the hole in the slide, should have the stock spring in it. The old slide has two holes in it, one dead center and one off center. not sure if thats how they come.
As far as installing an AFR gauge, I just dont want the bung in my pipe or the gauge on the bike and I dont want to spend the money on a one time usage thing.
If I were constantly changing things on the bike, I would absolutely put one on her, but I figure once its dialed in, I should be good for another 22 years.
The bike starts easily, idles nice and runs great at anything over that 1/8 throttle. No pops on de-acceleration.
At any speed, when just barely on the throttle, it is not smooth, a bit jerky... I can tell when she moves to the high circuit. Ive adjusted the low speed mix screw in 1/8 increments clockwise until almost seated and counterclockwise until its almost falling out. In the middle about 2 1/2 - 2 3/4 turns out from seated, is best, but still not smooth.
I was originally concerned about the 150 main, but I understand that to be an air jet and only really in play when the slide moves up... is that right?
I called the guy that tuned this carb 22 years ago;
He says what he did was change the jets and enlarged the hole in the slide, should have the stock spring in it. The old slide has two holes in it, one dead center and one off center. not sure if thats how they come.
As far as installing an AFR gauge, I just dont want the bung in my pipe or the gauge on the bike and I dont want to spend the money on a one time usage thing.
If I were constantly changing things on the bike, I would absolutely put one on her, but I figure once its dialed in, I should be good for another 22 years.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,081
Likes: 2,159
From: Ohio
While the idle mixture screw is commonly only under operation until just off idle to 1/8 throttle, RPM is not as relevant to when that fuel passage is in play. For instance, if you're doing a dyno pull and slam the throttle closed even though the engine is spinning down from 6000 rpm you bet your *** the idle mixture passage is dumping 100% of its fuel because the throttle is closed and the bike is still running.
Sweet spot is 3 turns out on the idle mixture screw at anything less than 2000' elevation. Have you removed the plug from where the idle mixture screw is located?
Sweet spot is 3 turns out on the idle mixture screw at anything less than 2000' elevation. Have you removed the plug from where the idle mixture screw is located?