Carb / Air filter issues
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2nd Gear
Joined: Jul 2024
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From: London Ontario
Carb / Air filter issues
2006 Softail Standard TC 88, recently changed air filter from a k&n filter under the stock cover to a 90 degree cone filter. Bike ran great beforehand. With the new filter I can get it started on the side stand, when I stand it up it either stalls out, or if I keep revving it will idle again and runs fine while riding, except at a hard stop, it sometimes tries to die out again. Stock carb, Vance big radius 2-1 pipe, 48 pilot, 195 main in it when I got it. After it stalls out it's really hard to start again unless I use the choke for a few seconds then let it off. It bogs sometimes on acceleration from a dead stop only. And usually only after the stalling starts happening.
This is blowing my mind. I oiled the new filter, it's a cotton filter. Idle screw is 2 1/4 turn out. If I put the old AC back on, runs like a top again. New AC has a vent hole in it, and it lines up with the one in the carb. HELP.
This is blowing my mind. I oiled the new filter, it's a cotton filter. Idle screw is 2 1/4 turn out. If I put the old AC back on, runs like a top again. New AC has a vent hole in it, and it lines up with the one in the carb. HELP.
Road Captain
Joined: Jul 2023
Posts: 520
Likes: 401
From: So Western Ohio
I'm familiar with the K&N reusable filters but is the cotton filter reusable and are you supposed to oil it?
If so, sometimes guys put way too much oil on a filter. If it's dripping with oil wash it, dry it and redo it with the recommended light oiling.
Could that be it?
If so, sometimes guys put way too much oil on a filter. If it's dripping with oil wash it, dry it and redo it with the recommended light oiling.
Could that be it?
Last edited by Rufus13; Jul 28, 2024 at 01:54 AM.
Seasoned HDF Member
Joined: Sep 2008
Posts: 14,146
Likes: 11,219
From: San Diego, CA
2006 Softail Standard TC 88, recently changed air filter from a k&n filter under the stock cover to a 90 degree cone filter. Bike ran great beforehand. With the new filter I can get it started on the side stand, when I stand it up it either stalls out, or if I keep revving it will idle again and runs fine while riding, except at a hard stop, it sometimes tries to die out again. Stock carb, Vance big radius 2-1 pipe, 48 pilot, 195 main in it when I got it. After it stalls out it's really hard to start again unless I use the choke for a few seconds then let it off. It bogs sometimes on acceleration from a dead stop only. And usually only after the stalling starts happening.
This is blowing my mind. I oiled the new filter, it's a cotton filter. Idle screw is 2 1/4 turn out. If I put the old AC back on, runs like a top again. New AC has a vent hole in it, and it lines up with the one in the carb. HELP.
Based on the highlighted info, it strongly suggests that the issue is with the new filter.
I suggest checking the following 3 things:
1) Proper oiling of the new filter, as suggested above.
2) Make sure you installed the new "90° cone filter" properly. (and check you didn't block the breathers).
3) Retune the carb...
As to #3, carbs are not as resilient as EFI. They supply the fuel they are tuned to supply... no more, no less. Your exhaust is short, with little restriction, and hard to tune. Even with a K&N filter, the OEM air cleaner assemblies are rather restrictive. I suspect you made a big change in airflow into the engine with new air cleaner assembly. The fact that the enricher helps it to run & not stall, and it bogs on acceleration from a dead start, suggests you are running lean in the idle/mid range areas of the carb tune...
After checking the #1 & #2 points above, and finding them to be OK, I would retune the bike. Start with your mixture screw, see where it ends up. That will tell you if you need to change the pilot jet. You may even look into a different needle. After dialing in the idle/mid range, you may be fine with the main jet.
I don't know you expertise with the OEM Keihin CV40 carb, but I believe it to be a good carb, sufficient up to about 110HP. I have loved the two bikes I have that use them (I still own one of them). They are easy to tune and to clean/rebuild. The predecessor to the CV40, the Keihin butterfly carb, I didn't like so much.. sadly the butterfly carb's poor reputation has spilled over to the CV40 carb.
Here is a good reference for CV40 carb, as well as parts... CV Performance.
https://cv-performance.com/instructions-guides
Good luck with dialing in that carb...
Last edited by hattitude; Jul 28, 2024 at 08:34 AM.
Thread Starter
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2nd Gear
Joined: Jul 2024
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From: London Ontario
I would agree, if it wasn't doing this before I oiled it, and it got a little bit better when I did. But most cotton filters need to be oiled as far as I have learned, I could be wrong. Unfortunately the air filter didn't come with instructions. But in the past with other bikes, cotton filters always got oiled, and they worked. I could be wrong. Like I said though it was actually worse when I oiled it. Another thing to note, there is a strong smell of gas when it stalls out, almost like it's flooded. Which made me think float height. But why would float affect one cleaner and not the other? I'm so baffled by this. Could it be that my slow jet is too big for this filter and not the other? Would that make it stall when standing it up?
Seasoned HDF Member
Joined: Sep 2008
Posts: 14,146
Likes: 11,219
From: San Diego, CA
I would agree, if it wasn't doing this before I oiled it, and it got a little bit better when I did. But most cotton filters need to be oiled as far as I have learned, I could be wrong. Unfortunately the air filter didn't come with instructions. But in the past with other bikes, cotton filters always got oiled, and they worked. I could be wrong. Like I said though it was actually worse when I oiled it. Another thing to note, there is a strong smell of gas when it stalls out, almost like it's flooded. Which made me think float height. But why would float affect one cleaner and not the other? I'm so baffled by this. Could it be that my slow jet is too big for this filter and not the other? Would that make it stall when standing it up?
It would be nice if you would share the new filter make/model, or even a picture. The 90° air cleaners I have seen, would be far less restrictive than an OEM housing. It's concerning it didn't come with instructions. That suggests it's a cheap Chinesium part. If so, it could be a big part of the issue.
In any case, If the air cleaner is installed properly, and the filter is oiled (or not oiled) as required, a retune of the carb is in order. Always tune the same way, don't jump around switching parts. Start with the mixture screw and go from there...
Thread Starter
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2nd Gear
Joined: Jul 2024
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From: London Ontario
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Road Master
Joined: Oct 2019
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From: Connecticut
There's a spot on the flange of the 90 that needs to be ground out to allow air to a carb tansfer port.
Take it apart again and look closely you'll see what I'm talking about.
Take it apart again and look closely you'll see what I'm talking about.
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Thread Starter
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2nd Gear
Joined: Jul 2024
Posts: 6
Likes: 8
From: London Ontario
Talking about the small hole beside one of the mounting bolts at about at 10 o'clock position in the carb?
Thread Starter
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2nd Gear
Joined: Jul 2024
Posts: 6
Likes: 8
From: London Ontario
You sir, nailed it. I checked that the vent hole on the backing plate wasn't blocked before. But I never checked where it went, turns out the 90 degree flange just blocked it off from their own backing plate. Great design lmao. I just drilled a hole to feed it into the pipe on the flange. And my bike is running great now. You nailed it. Props bro
