CV carb air fuel mixture adjustment
Grand HDF Member
Joined: Sep 2017
Posts: 3,757
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From: Southern Virginia
Back in my CV40 days, I've tuned a bunch of them. From an 883 or 1200 Sportster, Evo, or Twinkie, here's my rules of thumb:
Idle mixture screw 3 turns out
45 Pilot
#4 brass washer under needle
Main based on displacement. I recall a 170 was a good fit in a 1200cc warmed over Sporty, so I'd toss a 180 main in your CV and run it.
BTW, doing plug chops and checking the ceramic around the electrode was a good way to see a tune, but with today's unleaded fuels and the hot plugs Harleys tend to run, it's not too reliable anymore. That soot around the threaded part is totally normal because it's much colder than the electrode is.
Idle mixture screw 3 turns out
45 Pilot
#4 brass washer under needle
Main based on displacement. I recall a 170 was a good fit in a 1200cc warmed over Sporty, so I'd toss a 180 main in your CV and run it.
BTW, doing plug chops and checking the ceramic around the electrode was a good way to see a tune, but with today's unleaded fuels and the hot plugs Harleys tend to run, it's not too reliable anymore. That soot around the threaded part is totally normal because it's much colder than the electrode is.
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Seasoned HDF Member
Joined: Nov 2006
Posts: 21,014
Likes: 19,118
From: The Wasteland
Matt makes a good point about washers under the needle. I got started with that as a kid on jap bikes. When you open up the intake and exhaust those raised needles can get back that little dip in the midrange. On my 03 Dyna I have V&H Short Shots with the free flowing baffles. I actually had to go with three washers because of how anemic the midrange was. Smartest thing to do would be to get a better set of pipes, but I love how compact the short shots are. It really makes it easy to work on the bike without a large exhaust system. Nothing hanging out to ding and scratch either.
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Seasoned HDF Member
Joined: Nov 2006
Posts: 21,014
Likes: 19,118
From: The Wasteland
There are baffles in them.
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Seasoned HDF Member
Joined: Nov 2006
Posts: 21,014
Likes: 19,118
From: The Wasteland
If you're turning the IMS clockwise, you are making it leaner. A 42 pilot and 165 seem lean for a 1340, as I have bigger jets in my 1250.
"I turned it all the way in clockwise and nothing happened." That would indicate to me that the throttle plate is not closed enough at idle, and you're running on the transfer ports. Back your idle speed down and try fiddling with the idle mix screw again. I was getting some decel popping and kept richening the IMS which did not help. Then, I backed the idle speed down, readjusted the IMS (leaner), and voila, no more decel popping. I was obviously running a bit on the transfer ports.
I might be worth pulling your pilot jet and idle mix screw, blasting out the passages and ports, just to make sure there's no boogers in the passages. I have been adding some Seafoam to each tank of gas, which keeps the jets clear. I ran without it for a while an could tell the pilot jet was getting clogged as it started a bit of decel rumbling/popping, which cleared up immediately after a dose of Seafoam. Actually, I use WM Motor Treatment, which is probably the same a Seafoam for considerably less. All I know is that it keeps my carb happy and supposedly stabilizes the fuel if I don't get a ride in at least every couple weeks.
I'd say 2.5 turns out is a good place to start, but set that idle speed low and then fiddle with the IMS. You can always set the idle speed after you've found the sweet spot with the IMS, but you need those transfer ports taken out of the equation.
John
"I turned it all the way in clockwise and nothing happened." That would indicate to me that the throttle plate is not closed enough at idle, and you're running on the transfer ports. Back your idle speed down and try fiddling with the idle mix screw again. I was getting some decel popping and kept richening the IMS which did not help. Then, I backed the idle speed down, readjusted the IMS (leaner), and voila, no more decel popping. I was obviously running a bit on the transfer ports.
I might be worth pulling your pilot jet and idle mix screw, blasting out the passages and ports, just to make sure there's no boogers in the passages. I have been adding some Seafoam to each tank of gas, which keeps the jets clear. I ran without it for a while an could tell the pilot jet was getting clogged as it started a bit of decel rumbling/popping, which cleared up immediately after a dose of Seafoam. Actually, I use WM Motor Treatment, which is probably the same a Seafoam for considerably less. All I know is that it keeps my carb happy and supposedly stabilizes the fuel if I don't get a ride in at least every couple weeks.
I'd say 2.5 turns out is a good place to start, but set that idle speed low and then fiddle with the IMS. You can always set the idle speed after you've found the sweet spot with the IMS, but you need those transfer ports taken out of the equation.
John
Bumped the idle back up to around 1000 and took a ride. It seems to be better but I only got to run about 10-15 miles. Ill know better once I get a few miles on the old girl.
Grand HDF Member
Joined: May 2014
Posts: 3,822
Likes: 1,170
From: florida
45 slow jet
180 main jet
IMS 1.5-2.0
you would have to experiment or have it on the dyno to really know the cruise ligh throttle application, but i have done it befoe
m
180 main jet
IMS 1.5-2.0
you would have to experiment or have it on the dyno to really know the cruise ligh throttle application, but i have done it befoe
m
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