Another CV40 question
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Tourer
Joined: Jul 2019
Posts: 487
Likes: 446
From: Lithgow NSW Australia
Another CV40 question
G'day Fellas.
Trying to tune a mates 1999 FLSTF. It has a K&N air filter and V&H pipes, other than that stock. Only done 18,000Km. I just serviced it and found an air leak at the front inlet flange. New rubbers installed and no air leaks now. Checked and cleaned the carb, it had 48 pilot and 200 main jets
. At idle I could screw the pilot screw all the way in and it would still run. I tried with a 45 and the same. I put a 42 in and the pilot screw seems happy at 1 turn out. I'm in two minds as to whether or not try a 40. I would think with the K&N and V&H pipes (no baffles) it would need larger. Any thoughts.
Cheers
Trying to tune a mates 1999 FLSTF. It has a K&N air filter and V&H pipes, other than that stock. Only done 18,000Km. I just serviced it and found an air leak at the front inlet flange. New rubbers installed and no air leaks now. Checked and cleaned the carb, it had 48 pilot and 200 main jets
. At idle I could screw the pilot screw all the way in and it would still run. I tried with a 45 and the same. I put a 42 in and the pilot screw seems happy at 1 turn out. I'm in two minds as to whether or not try a 40. I would think with the K&N and V&H pipes (no baffles) it would need larger. Any thoughts.Cheers
Grand HDF Member
Joined: Apr 2007
Posts: 3,728
Likes: 3,073
From: Brighton, MI
Is your mate the original owner? The reason I ask is known history vs unknown history with what has been doe to the bike.
My first thought is check float height. A 42 slow seems small for a bike with free flowing AC and pipes. What do the plugs look like?
EDIT: Forgot to mention, check the air mix screw for condition. Any wear to the tip of the mix screw? Condition of the small O-ring on the mix screw? Is that O-ring and the small washer intact? If the rubber O-ring was "missing", chances are it is stuck in the threaded bore. (common)
What kind of needle and any shims to the needle? Check for wear in the needle and check NEEDLE JET for wear. The needle jet can get worn letting fuel in even at idle because of wear. Has the air bleed hole in the slide been drilled?
Check the emulsion tube to see if it is OEM or maybe a dynojet kit has been installed? Dynojet kits make the bike run rich and the emulsion tube will have only a couple of holes drilled in it vs OEM having like 10 holes. Dynojet also uses a different numbering system to the main jet with the 200 being a common size for their kit. The emulsion tube holes will clue you in as to if you have the dynojet kit.
Check float level first. If the carb has OEM parts, put a 190 main jet in because a 200 is too big (again if it's an OEM jet) and then see if the 42 becomes "too lean". If a new OEM main jet does not fit in the emulsion tube, then again, chances are you have a dynojet kit. Those kits have a tendency to run rich.
The above is a good starting point and my initial thoughts with only a couple sips of coffee in me. It's morning time here is the states and stayed up late celebrating our "Independence Day".
My first thought is check float height. A 42 slow seems small for a bike with free flowing AC and pipes. What do the plugs look like?
EDIT: Forgot to mention, check the air mix screw for condition. Any wear to the tip of the mix screw? Condition of the small O-ring on the mix screw? Is that O-ring and the small washer intact? If the rubber O-ring was "missing", chances are it is stuck in the threaded bore. (common)
What kind of needle and any shims to the needle? Check for wear in the needle and check NEEDLE JET for wear. The needle jet can get worn letting fuel in even at idle because of wear. Has the air bleed hole in the slide been drilled?
Check the emulsion tube to see if it is OEM or maybe a dynojet kit has been installed? Dynojet kits make the bike run rich and the emulsion tube will have only a couple of holes drilled in it vs OEM having like 10 holes. Dynojet also uses a different numbering system to the main jet with the 200 being a common size for their kit. The emulsion tube holes will clue you in as to if you have the dynojet kit.
Check float level first. If the carb has OEM parts, put a 190 main jet in because a 200 is too big (again if it's an OEM jet) and then see if the 42 becomes "too lean". If a new OEM main jet does not fit in the emulsion tube, then again, chances are you have a dynojet kit. Those kits have a tendency to run rich.
The above is a good starting point and my initial thoughts with only a couple sips of coffee in me. It's morning time here is the states and stayed up late celebrating our "Independence Day".
Last edited by Yankee Dog; Jul 5, 2025 at 06:35 AM.
Thread Starter
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Tourer
Joined: Jul 2019
Posts: 487
Likes: 446
From: Lithgow NSW Australia
G'day Bubba.
Yes I thought so too and put a 190 in it. Haven't road tested yet.
G'day Yanky Dog.
Old (75) mate bought the bike new and only done 18,000Km (11,000 miles) in 25 years
He doesn't think anyone has taken the manifold off but one rubber was distorted and leaking. May be the shop tried to jet to compensate
He said the shop that did the air filter put the 48 pilot jet in but didn't know who put the 200 main in. Float height is 10.5mm (book says 10.5-11.5). Air screw, O ring, washer & spring look original and good. Needle and jet look original and good condition (no shim under needle). The slide doesn't look to be drilled and he hasn't put a Dynojet kit in it. I'll pull the emulsion tube to check tonight but my jets fit straight in.
What I find strange is the 6 little holes up stream of the hole with the air screw. They come from the same passage so even with the air screw all the way in the motor will suck fuel through those holes governed by the pilot and air jets.
My bike with the same carb & air filter (std pipes) runs great with 45/185 & 0.5mm shim under the needle.
Cheers
Yes I thought so too and put a 190 in it. Haven't road tested yet.
G'day Yanky Dog.
Old (75) mate bought the bike new and only done 18,000Km (11,000 miles) in 25 years
He doesn't think anyone has taken the manifold off but one rubber was distorted and leaking. May be the shop tried to jet to compensate
He said the shop that did the air filter put the 48 pilot jet in but didn't know who put the 200 main in. Float height is 10.5mm (book says 10.5-11.5). Air screw, O ring, washer & spring look original and good. Needle and jet look original and good condition (no shim under needle). The slide doesn't look to be drilled and he hasn't put a Dynojet kit in it. I'll pull the emulsion tube to check tonight but my jets fit straight in.
What I find strange is the 6 little holes up stream of the hole with the air screw. They come from the same passage so even with the air screw all the way in the motor will suck fuel through those holes governed by the pilot and air jets.
My bike with the same carb & air filter (std pipes) runs great with 45/185 & 0.5mm shim under the needle.
Cheers
Grand HDF Member
Joined: Apr 2007
Posts: 3,728
Likes: 3,073
From: Brighton, MI
Those little holes are called the transfer ports. They keep the bike running when the throttle plate is closed.
My guess is going to be old dried up and leaky intake manifold seals. Especially if original. Sucking in air. I agree, compensated for by the richer/larger jets. Replace those and the carb to manifold seal, even if you think that is good, just replace it.
My guess is going to be old dried up and leaky intake manifold seals. Especially if original. Sucking in air. I agree, compensated for by the richer/larger jets. Replace those and the carb to manifold seal, even if you think that is good, just replace it.
Thread Starter
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Tourer
Joined: Jul 2019
Posts: 487
Likes: 446
From: Lithgow NSW Australia
G'day YD.
All rubbers replaced with new. No air leaks at all.
Mate said the manifold had never been off so the cocked rubber had been there since factory!!!
So when throttle is closed the butterfly is supposed to be fully shut? This has about a 5 thou" opening. That might explain it!
Sorry mate, I've been playing with old Amals all my life.
Cheers
All rubbers replaced with new. No air leaks at all.
Mate said the manifold had never been off so the cocked rubber had been there since factory!!!
So when throttle is closed the butterfly is supposed to be fully shut? This has about a 5 thou" opening. That might explain it!
Sorry mate, I've been playing with old Amals all my life.
Cheers
When the throttle is closed the butterfly should still be open just a little bit, even at idle there needs to be a little air flow
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Seasoned HDF Member
Joined: Dec 2010
Posts: 7,736
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From: Coromandel Peninsula New Zealand
On Aussie and NZ fuel, 200 main isn't as out there as our American cousins may think.
I ran a 200 on my 1998 Wide Glide, with an EV27 cam.
I ran a 200 on my 1998 Wide Glide, with an EV27 cam.
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Thread Starter
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Tourer
Joined: Jul 2019
Posts: 487
Likes: 446
From: Lithgow NSW Australia
G'day Spanners.
I run mine (88FXST) on 98 (no ethanol) and a 185 mains, she loves it.
Still waiting for the new choke cable so I whacked a #50 pilot jet in just to see.
Cheers
I run mine (88FXST) on 98 (no ethanol) and a 185 mains, she loves it.
Still waiting for the new choke cable so I whacked a #50 pilot jet in just to see.
Cheers
HDF Community Team
Joined: Dec 2005
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From: NC USA
