Author Topic: CV 40 carb, no fast idle when choke is out  (Read 1727 times)

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Offline mokeypoole

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CV 40 carb, no fast idle when choke is out
« on: Thursday, June 09, 2011. 07:35:48 PM. »
I have a 1998 stock FXD.  The engine does not increase idle speed when the choke is pulled out.  I have had the bike 4 years and it has never sped up the idle when the choke is pulled out.  The choke works because it gives it enough extra gas to start when cold.  On my other bikes, 1995 sportster and 2004 Road King, whenever the choke is out the bike idles faster than when it is in.

Any ideas why this might be?  O bought the bike used but I replaced all the parts in the carb with stock.  That would be emulsion tube, spring, and neddle.  The jets are 45 and 180.

Offline PC_Hater

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Re: CV 40 carb, no fast idle when choke is out
« Reply #1 on: Friday, June 10, 2011. 12:07:00 AM. »
Do you live somewhere hot? I really can't imagine why the idle doesn't increase when the choke is out.
On my Sportster a couple of tweaks of the throttle to make the accelerator pump work is often all that is needed in summer.
Are you sure that isn't what you are doing and the choke has never worked?
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Offline Bruno-Katz Fokkerpilot

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Re: CV 40 carb, no fast idle when choke is out
« Reply #2 on: Friday, June 10, 2011. 02:18:16 AM. »
I got this problem with my Mikuni. The bike starts just fine but the fast idle is only about 1,000 RPM. Once the bike is warmed up and i push the choke in it runs just fine. If i pull the choke out while the bike is hot, the RPM goes up to around 1800 RPM. so it is working ok. Go figure?  :scratch:
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Offline Ridetard

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Re: CV 40 carb, no fast idle when choke is out
« Reply #3 on: Friday, June 10, 2011. 04:01:14 AM. »
Sounds to me like the carb requires adjusting.

Offline PC_Hater

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Re: CV 40 carb, no fast idle when choke is out
« Reply #4 on: Friday, June 10, 2011. 05:06:52 AM. »
Bruno, that is how the choke is meant to work.
Pulling the choke out doesn't mean "I want a fast idle please", it means "I would like the bike to start on this cold day".

In general we are lazy, so we pull the choke all the way out, push the Start button, the bike starts, revs at 2000 rpm or whatever and we immediately push the choke back to the half way mark or so. The bike has a fast tickover and if it is too fast we push the choke in a bit further. Riding along we gradually push the choke  all the way in.

If we were not lazy we would think 'Ah, this morning the temperature is 6 degrees C, therefore I will pull the choke out exactly 3/8 of its travel'.

In your case you pull the choke out when the bike is hot and you get a fast tickover, that is correct operation. If you want your cold start to tickover faster you will have twiddle something in the Mikuni, but why do you need a faster tickover than 1000rpm? Does the bike start and tickover on those sub-zero days in winter? If it does everything is as it should be.

And Ridetard is correct, that CV40 isn't quite right.
« Last Edit: Friday, June 10, 2011. 05:10:31 AM. by PC_Hater »
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Offline mokeypoole

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Re: CV 40 carb, no fast idle when choke is out
« Reply #5 on: Friday, June 10, 2011. 05:22:31 AM. »
even once the bike warms up and I pull it out the idle does not jump up past 1100.  The normal idle is set at 1000.  I don't understand it.  I have two other bikes so I am sure I am not doing something wrong with my starting procedure.

Even when its 30 degrees outside and I start the bike, I have to use the choke to start it.

When its 100 degrees outside I don't have to use the choke

I have cleaned all the air passages but still can't find the problem

Local dealer told me as long as it starts not to worry about it but I like the way the fast idle condition lets you know you forgot to push the choke in

Offline PC_Hater

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Re: CV 40 carb, no fast idle when choke is out
« Reply #6 on: Friday, June 10, 2011. 05:37:03 AM. »
So, the choke really is working then.
My best guess is that the choke cable is not adjusted properly, it lifts the choke enough to let more fuel through but not enough to give a really fast tickover. The dealer is right, the carb is doing what it should and working well. I don't need a 2000rpm cold tickover, it is just that in my case that is what it does and life is too short to try and slow my on-choke tickover down!
1942 WLA45 chop, 1999 FLTRI, 2000 1200S

Offline Bruno-Katz Fokkerpilot

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Re: CV 40 carb, no fast idle when choke is out
« Reply #7 on: Friday, June 10, 2011. 05:41:20 AM. »
Thanks for that PC, i`m reasured. Regardz, Bruno.
Peace...those brief moments in history when everyone stands around reloading....

Offline mokeypoole

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Re: CV 40 carb, no fast idle when choke is out
« Reply #8 on: Friday, June 10, 2011. 06:36:35 AM. »
So, the choke really is working then.
My best guess is that the choke cable is not adjusted properly, it lifts the choke enough to let more fuel through but not enough to give a really fast tickover. The dealer is right, the carb is doing what it should and working well. I don't need a 2000rpm cold tickover, it is just that in my case that is what it does and life is too short to try and slow my on-choke tickover down!

there is no adjustment on the stock harley choke cable

Offline HotRock

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Re: CV 40 carb, no fast idle when choke is out
« Reply #9 on: Saturday, June 11, 2011. 11:44:28 AM. »
The choke (or enrichener) allows more fuel and air for starting.   If it doesn't idle fast I would suspect that an air passage somewhere in the enrichener circuit is blocked or clogged with debris.

Offline mokeypoole

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Re: CV 40 carb, no fast idle when choke is out
« Reply #10 on: Saturday, June 11, 2011. 03:01:07 PM. »
The choke (or enrichener) allows more fuel and air for starting.   If it doesn't idle fast I would suspect that an air passage somewhere in the enrichener circuit is blocked or clogged with debris.

Do you know where the air passage is for the choke circuit?  I have cleaned the carb several times and still no change

Offline rbabos

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Re: CV 40 carb, no fast idle when choke is out
« Reply #11 on: Sunday, June 12, 2011. 06:44:46 AM. »
The choke (or enrichener) allows more fuel and air for starting.   If it doesn't idle fast I would suspect that an air passage somewhere in the enrichener circuit is blocked or clogged with debris.

Do you know where the air passage is for the choke circuit?  I have cleaned the carb several times and still no change
Hotrock is correct. Fuel and air increase at the same time to get richness and increased speed to keep the cold engine running. Not familiar with that carb, but others I've seen use a seperate jet and air passage directly related to the plunger bore of the enricher. I think if you study it really carefully you will trace it to a blocked air passage.
Ron
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Offline truck

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Re: CV 40 carb, no fast idle when choke is out
« Reply #12 on: Sunday, June 12, 2011. 06:46:28 AM. »
From what I've read here it seems the "choke" is working fine, motor starts when it's cold.
Mine works a little goofy too. Sometimes the idle is around 1,500rpm and sometimes around 1,200rpm.
If the motor starts and gets the bike moving.....if it ain't broke, don't fix it. :teeth:
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Offline HotRock

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Re: CV 40 carb, no fast idle when choke is out
« Reply #13 on: Sunday, June 12, 2011. 06:59:18 AM. »
There is an air port or hole in the carb body leading to the enrichener valve.  This port is located in the area under the slide vacumn diaphragm.  This port is blocked when the Enrichener  cable is pushed inward which cuts off the extra fuel for cold starts and air for faster idle.   
Some say that if it starts, then it is working and don't worry about it.  You can compensate by opening the throttle for the necessary idle speed when the engine is cold.    That may be correct in that it will start, however the author of this thread wants his fast idle to work properly.   

Offline mokeypoole

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Re: CV 40 carb, no fast idle when choke is out
« Reply #14 on: Sunday, June 12, 2011. 06:43:48 PM. »
Thanks HOt Rock.  Thats what I needed to know.  Your exactly right.  It may work but it is not right and I want it right

Mike

Offline fourthgear

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Re: CV 40 carb, no fast idle when choke is out
« Reply #15 on: Monday, June 13, 2011. 03:17:24 PM. »
If the idle doesn't increase with the opening of the enricher , some things not right. Blocked passage , as said or a broken or unattached enricher cable .

Both my Pan's have CV40's on them & they both will have a high idle (after pulling cable out )until I ether close the enricher or adj. it to keep a high enough idle to keep them running .