Speaking of cv carbs

[76shuvlinoff]

The other cv  thread has me interested again.

93" S&S "shovel" long block, Andrews 7 cam, dual plugged heads, 2Ki sparker, thunderheader.

I had a 40mm cv on it with a Leineweber cam that did not have enough duration and gave me 205-210 cyl pressure. It always cranked hard but once it was running it had great manners. The Andrews 7 got me down to 185 psi. Then I did something stupid and changed to a 44cv without a test ride. Since then the bike has been real cold blooded. Once good and hot it's fine. I have not tinkered with needles or jetting.

My question: is a 40mm cv adequate to run a 93" mill well into it's top end? I could not get there with the other cam.  I am tempted to go back to the smaller carb for the next season just to see how it behaves now.

[Hossamania]

Do you leave the enrichener on for a while, or do you push it in as soon as it will idle without killing? I run with mine on and let it go in by itself, works best for me that way.
Do you know what jets and needle are in there now?

[Hossamania]

You know the smaller carb couldn't keep up with the old cam, but the new cam doesn't change your displacement, and will still need a lot of fuel and air on the top end. I would work on the 44 first. You know it works when warm, try and get the cold manners dialed in.

[Ohio HD]

Mark, here's some carburetor flow data from a shootout test that Mr. Max put together some time back. The entire report is too large to post, so here is just the flow numbers.

The CV40 data with or without a backing plate shows the flow at about 160 cfm @ 10. The CV51 at 1.55% more, about 250 cfm @ 10. So in my best guess, the CV44 can't be tremendously more flow that the CV40, I would guess around 20% more, or about 192 cfm @ 10.

I would try to jet the CV44 more to your motor. I don't think its at all too much carburetor, as the S&S E is 197 cfm @ 10.


[attach=0]

[76shuvlinoff]

Thanks guys, since I never write a damn thing down I'd have to open the carb to see what's in it. As I recall I could not kill the motor when I bottomed the idle screw so there's something else going on with it. When I parked it on the lift this fall it was overflowing so I need to take it apart anyhow.

Hoss,
I usually let it idle maybe a minute but not much more then shove the enrichener in and go. A 1/2 mile away at the first stop the idle sucks, at 2 miles it still isn't smooth but at 6-8 miles it's fine.  The 40mm was pushbutton but seemed to come up a little softer at the top. The E I have on the shelf was good at the top but I never got it smooth down low.  I don't even try to pretend to be a carb guy.

Fuel injection has spoiled me 

[Ohio HD]

Mark, HD J01696 has part numbers of items you may need.

https://serviceinfo.harley-davidson.com/sip/content/document/view?parameters=highlight%3D27934-99&id=1310


I also had this stashed away, HD numbers for jets and needles. I haven't verified their accuracy or if even available. Was just some data I ran across once and saved.


HD Tuner Kit (P/N 27419-99)
Main Jets
number 200 - 27105-88
number 210 - 27726-99
number 220 - 27775-99
number 230 - 27776-99
number 240 - 27778-99
number 250 - 27779-99

Spring 130/210 gm 27728-99

Slow Jets (3)
number 48 - 27165-90
number 50 - 27724-99
number 52 - 27780-99

Jet Needles (Listed Lean to Rich)
27727-99
27933-99
27967-99
27968-99

[Hossamania]

Leave the enrichener on when you start riding, it will idle down after a bit. CV carbs aren't like the E carbs when cold.
Like you said, once you get into it you may find an issue, and might have to play with jetting a bit.
If you can find the tuner kit Ohio listed, get it.

[FSG]

J01696   SCREAMIN' EAGLE® BIG BORE 44 mm CV CARBURETOR KIT, 27934-99

[72fl]

J01696   SCREAMIN' EAGLE® BIG BORE 44 mm CV CARBURETOR KIT, 27934-99

I have a Screaming Eagle sitting out in the garage, it has a Black plastic knob to pull up for enrichner. Needs to be gone through as that will be done in the Spring. It has been a while since I looked at it, it has a what appears to be a Black Plastic type of adapter on one end of it, I don't see it in the parts break down drawing you attached, any idea what it is used for ?

[Hogman]

Just a Thought 72, First off, IF it's Plastic, I Really DON'T Know, But IF it's a Rubber Piece, it could very well be the Adapter to the Manifold. A Pic Might be Helpful in This, 72. Good Luck!!!!




ME

[JW113]

Mark, the general rule of thumb with the CV40 is, on an Evo, they start to nose over around 90HP. Just my humble opinion, but seeings how the Shovelhead ports & valve angles don't typically flow as well as the Evo, I think a CV40 is plenty of carb for 93" Shovelhead motor for general street duty. If you were tuning for max HP for the drag strip, perhaps not, but I know that's not what you have in mind.

That said, the CV44 should be able to be tuned to resolve the cold blooded behavior. If you can dial in the idle jet clear to the seat and the motor is still running, that indicates that you have the throttle plate (idle speed screw) adjusted such that it's past the low speed transfer ports, and they are now acting like your idle jet. If you can pull the carb and look at the back end, you will likely see this is the case.

I fought a similar issue with mine, and I think it has to do with cam selection. Performance cams tend have poor manifold vacuum at idle, and don't pull enough air/fuel to keep the motor running. So the natural tendency is to open the idle speed screw to get it to idle. This has the consequence of exposing the transfer ports. The usual solution then is to drill an air bleed hole in the throttle plate, so that more idle air can get past the plate without having to open the plate past the transfer ports. It took me three or four attempts to find the right size bleed hole, of course starting small and gradually increasing.

On the cold blooded behavior, in general that's not such a bad thing other than the stumbling and coughing you have to endure until the motor gets warmed up nice and hot. My Ironhead is exactly that way also, so the solution is to use ever so much enrichener to get past that without trashing the spark plugs. Of course if you want to try and tune it the starting place is with the low speed jet. I typically use a 45 or 48. You can try increasing beyond that but your fuel mileage will take a hit at 50 or beyond. The other thing that can help the CV is to lift the slider needle with some shims, to get it into the tapered region sooner.

cheers,
JW

[david lee]

Mark, the general rule of thumb with the CV40 is, on an Evo, they start to nose over around 90HP. Just my humble opinion, but seeings how the Shovelhead ports & valve angles don't typically flow as well as the Evo, I think a CV40 is plenty of carb for 93" Shovelhead motor for general street duty. If you were tuning for max HP for the drag strip, perhaps not, but I know that's not what you have in mind.

That said, the CV44 should be able to be tuned to resolve the cold blooded behavior. If you can dial in the idle jet clear to the seat and the motor is still running, that indicates that you have the throttle plate (idle speed screw) adjusted such that it's past the low speed transfer ports, and they are now acting like your idle jet. If you can pull the carb and look at the back end, you will likely see this is the case.

I fought a similar issue with mine, and I think it has to do with cam selection. Performance cams tend have poor manifold vacuum at idle, and don't pull enough air/fuel to keep the motor running. So the natural tendency is to open the idle speed screw to get it to idle. This has the consequence of exposing the transfer ports. The usual solution then is to drill an air bleed hole in the throttle plate, so that more idle air can get past the plate without having to open the plate past the transfer ports. It took me three or four attempts to find the right size bleed hole, of course starting small and gradually increasing.

On the cold blooded behavior, in general that's not such a bad thing other than the stumbling and coughing you have to endure until the motor gets warmed up nice and hot. My Ironhead is exactly that way also, so the solution is to use ever so much enrichener to get past that without trashing the spark plugs. Of course if you want to try and tune it the starting place is with the low speed jet. I typically use a 45 or 48. You can try increasing beyond that but your fuel mileage will take a hit at 50 or beyond. The other thing that can help the CV is to lift the slider needle with some shims, to get it into the tapered region sooner.

cheers,
JW

another good summary jw

[76shuvlinoff]

Thanks JW, you've given me something to look for when I get into it. 


It's been a while but I do remember it was a struggle getting a decent idle when I put it on. I need to get in there fix my stuck float plus check the jetting and needle anyhow. You're right, I'm not looking for drag strip performance, just a "Potty mouth" eating grin once in awhile. 

And thanks to you all who commented plus Ohio and FSG for the parts info. I bookmarked this thread so I can come back to it.

[rageglide]

I ran a CV40 on a 95" Twincam, it had no issues pulling hard all the way to the rev limiter (6500).  Ran great

[koko3052]

I ran a CV40 on a 95" Twincam, it had no issues pulling hard all the way to the rev limiter (6500).  Ran great

BIG difference on intake flows from a twinky to a shovel!

[72fl]

J01696   SCREAMIN' EAGLE® BIG BORE 44 mm CV CARBURETOR KIT, 27934-99

I have a Screaming Eagle sitting out in the garage, it has a Black plastic knob to pull up for enrichner. Needs to be gone through as that will be done in the Spring. It has been a while since I looked at it, it has a what appears to be a Black Plastic type of adapter on one end of it, I don't see it in the parts break down drawing you attached, any idea what it is used for ?

It actually was an adapter on the outlet side touse on different 3 and 4 bolt type air cleaner assemblies.

[FSG]

A few months ago I gave a younger brother an unmolested CV from an 05 Fatty to put on an 84 FXEF, I've no idea what jets he's running in it although I should find out.

[76shuvlinoff]

A few months ago I gave a younger brother an unmolested CV from an 05 Fatty to put on an 84 FXEF, I've no idea what jets he's running in it although I should find out.

Probably fired right up and he hasn't been home since. 

[JW113]

Ha ha ha! Oh I mean Ho Ho Ho!

Don't know why, not a big fan of those rubber spiggot mounts that bolt to the Shov/Iron 2 bolt flange. Have become a fan of those adapters (from Killer Motorcycle Parts for example) that you JB weld to the CV and turn it into a 2 bolt flange. They are totally too cool for school IMO.

-JW

[FSG]

JW      I also told him that BUT ........  sometimes you have to work with what you can get hold of

[76shuvlinoff]

Ha ha ha! Oh I mean Ho Ho Ho!

Don't know why, not a big fan of those rubber spiggot mounts that bolt to the Shov/Iron 2 bolt flange. Have become a fan of those adapters (from Killer Motorcycle Parts for example) that you JB weld to the CV and turn it into a 2 bolt flange. They are totally too cool for school IMO.

-JW

Both CVs I've had on the 76 have those JB welded adapters. 

[rageglide]

I ran a CV40 on a 95" Twincam, it had no issues pulling hard all the way to the rev limiter (6500).  Ran great

BIG difference on intake flows from a twinky to a shovel!

No argument.  Only commented because many feel a CV40 is too small for a larger displacement engine. 

[Burnout]

Thanks guys, since I never write a damn thing down I'd have to open the carb to see what's in it. As I recall I could not kill the motor when I bottomed the idle screw so there's something else going on with it. When I parked it on the lift this fall it was overflowing so I need to take it apart anyhow.

Hoss,
I usually let it idle maybe a minute but not much more then shove the enrichener in and go. A 1/2 mile away at the first stop the idle sucks, at 2 miles it still isn't smooth but at 6-8 miles it's fine.  The 40mm was pushbutton but seemed to come up a little softer at the top. The E I have on the shelf was good at the top but I never got it smooth down low.  I don't even try to pretend to be a carb guy.

Fuel injection has spoiled me 

This is normal CV carb behavior Trying to improve cold running will usually result in a drop in mileage, and make it want to blacken spark plugs.

Like JW sez, The idle mix screw not stalling the motor is probably because the throttle plate is open too far and it is pulling fuel from the transfer port.
Some guys drill a hole in the butterfly to get the throttle plate to close more for a more tune able idle.
I don't know what size hole to drill, it probably varies with different setups, so this is a trial and error thing.
Throttle plate position should be verified before going down this rabbit hole.

I am also a big fan of the press/glue on carb adapters. The rubber works but not for the long run, and I don't care for the floppy fit.
Although the solid adapter still needs support at the air cleaner backing plate.

[Hybredhog]

    A 40cv will have higher vacuum at the carb than a 44cv, helping starting & low speed performance. So bigger jets in a 44 will probably be to rich, vs. what the carb was designed for, bigger C.I. (draw), & better flowing heads, not exactly a shovel's head can deliver on average. Just for an example on old Kiehin butterfly carbs, 74ci. typically used a slightly larger jets than 80ci. Just because it took bigger jets to just get more fuel into the cylinder from lack of draw. the same basic thing happens when you try a S&S on a sporty.
    what I've used on some transitional fuel delivery problems, is to use a small file & just make a very small notch on the butterfly in line with the idle feed hole. It lets a little earlier/ and wider delivery from the passage, and only marginally more opening of the idle screw. Also you want a stock size slide hole on the slide, so it doesn't open to early.   

[dirtymike]

I sure would like to see a pic of this notch.Is it a 90 degree cut or a round cut. Dirty

[Hybredhog]

 90 degree/ "v", it doesn't take much, Start small & get the feel for it. As mentioned before, drilling a hole in the butterfly can be an option, but a lot more sensitive in its location & size, like .030". But I've only used that on the early '89 xl CV's that don't have an accelerator pump, and some older Jap bikes w/ CV's. They have to be a bit richer pilot jet, & It kind of blows down across the transition orifices & creates its own accelerator fuel pulse.

[JW113]

Note that for the idle circuit, it does not operate from air flow over the idle jet hole like the main jet or transfer ports. At idle, the idle jet hole is behind the 'closed' throttle plate, there is almost no air flow at all, and intake manifold vacuum alone sucks fuel from the idle jet hole. You can put an idle air bleed hole almost anywhere in the throttle plate, and it won't make any difference. FYI, the one on my CV51 on a 113" TC is at least 1/8", maybe a little bigger...

The whole point is that at idle, you want fuel being sucked from the idle jet only, so you can control it. If the throttle plate needs to be opened enough to keep the engine running but crosses over the transfer ports, then you've lost fuel metering control from the idle jet circuit. My approach was to keep drilling the idle air bleed hole larger until I could see that the throttle plate at idle was between idle jet hole and transfer ports.

-JW

[david lee]

Note that for the idle circuit, it does not operate from air flow over the idle jet hole like the main jet or transfer ports. At idle, the idle jet hole is behind the 'closed' throttle plate, there is almost no air flow at all, and intake manifold vacuum alone sucks fuel from the idle jet hole. You can put an idle air bleed hole almost anywhere in the throttle plate, and it won't make any difference. FYI, the one on my CV51 on a 113" TC is at least 1/8", maybe a little bigger...

The whole point is that at idle, you want fuel being sucked from the idle jet only, so you can control it. If the throttle plate needs to be opened enough to keep the engine running but crosses over the transfer ports, then you've lost fuel metering control from the idle jet circuit. My approach was to keep drilling the idle air bleed hole larger until I could see that the throttle plate at idle was between idle jet hole and transfer ports.

-JW

another good reply

[Hybredhog]

   In my experience, I went with a hole to blend in flat spots during throttle movements, and I located the  small hole appox. a 1/4" above the transition orifices. I've used notches on the butterfly edge on all kinds of rig & carbs for the same reason, and it helps in cold blooded circumstances to ease into running temps.
   My CV51 on my 124+ is virtually untouched, other than a leaner needle. I believe it takes a really big engine to make them work right, and almost anything smaller may have issues of one form or another. If you were to talk to Bob Woods about his modified 51's , & why he get the big $$ for it, he's machining out the stock orifices, & inserts a plug with a new pattern. I believe he did use a BF hole on his smaller (42mm) rebuilds, & those are orifice located.

[76shuvlinoff]

Well this OF is learning a lot. I'd run out to the barn and diddle it but tuning on a shovel in MI in January seems iffy at best.
(At least that's my excuse today) 

[JW113]

Well I can't say about a CV51 needing a 124" or more to work right. HD was selling them at a time when their biggest displacement SE stuff was 113", which is what I have. I don't think it's the cubes that is the issue regarding how they performe at idle. There is hardly any air flowing through until you have the throttle opened up quite a bit. I think the problem that I had was with the cams, i.e. a whole lot of duration and overlap. That is what messes with carburation at idle. After adding an idle bleed hole to the throttle plate, it purrs like a kitten at idle and has no flat spots anywhere through the throttle range. Not to mention very polite street manners until you bang the throttle open. Then hold the <cuss> on.


Speaking of the engine size and CV, to me the whole point of using a CV type carb is that they are fairly immune to displacement. They act like a small carb at low throttle openings, then turn into a big carb at WFO. Here's an example. I had a 1000cc BMW twin with TWO 40mm Bing CV carbs on it. That's 40mm of carb for 500cc of displacement per cylinder. Contrast that to a TC88, which used one 40mm CV to feed 1450cc. The Beemer ran great, never seemed to be "over-carburated".

I think it is with large throat butterfly carbs like the S&S G and especially D that you want to avoid on anything less than large displacement motors.

JMHO!

-JW

[Burnout]

"S&S G and especially D that you want to avoid on anything less than large displacement motors."

This goes for an E on a small motor, I liken them to a barn door for air and a fire hose for fuel.

You need a certain amount of pressure drop across the carb to create a responsive fuel signal.

This is the CV advantage, it also benefits by accelerating the air flow across the feed point adding to the signal and promoting atomization.

[Hybredhog]

    When HD came out with the 51cv, I think they were just shooting in the dark for "something" to sell. People drank the Kool-Aid for awhile, but most had unsatisfactory results with them, same as the Holley two throat they tried selling. I have several 51's on the bench for extra parts, and they all came off bikes with "95" phase 3" builds, and ran like turds. A less aggressive cam would make them better for "mid-size" motors, but as you've found out there was "some assembly required", and you were creative enough to tinker with it, but most people weren't. Yes, a CV is a great concept to cover up engineering/ EPA flaws, like for a stock 883 before F.I. came along. But Harley brought a 12 ft. culvert to go under the driveway, and created more problems than not.
    HD sold theirs with an updraft manifold to get tank clearance, and semi-defeated the purpose. I, on my life's path to do "Potty mouth" the hard way, machined a S&S "G" manifold to fit, but it was to close to the tank (FXDXT), & eventually cracked the plastic dome. So I whittled a low clearance dome (1/8" shorter), from a block of aluminum, to feed my stubbornness.   

[FSG]

......  to feed my stubbornness

I like that     but isn't that we all do riding HDs   

[Ohio HD]

......  to feed my stubbornness

I like that     but isn't that we all do riding HDs   

   Yes         

[xlfan]

J01696   SCREAMIN' EAGLE® BIG BORE 44 mm CV CARBURETOR KIT, 27934-99

I have a Screaming Eagle sitting out in the garage, it has a Black plastic knob to pull up for enrichner. Needs to be gone through as that will be done in the Spring. It has been a while since I looked at it, it has a what appears to be a Black Plastic type of adapter on one end of it, I don't see it in the parts break down drawing you attached, any idea what it is used for ?

You describe a completely different carb than the CV. The SE carb you describe, is the early style high perf butterfly Keihin, also sold as an Andrews carb.

[76shuvlinoff]

Bump!
I need to service my TC EG brakes and the shovel sitting on the lift untouched for nearly 9 months finally got to me. I uncovered Obnoxious and felt pretty bad when I saw the feed and mice "Potty mouth" on the seat. Didn't find any other rodent damage... yet but she's dusty and crusty, even a little rusty.

I turned on the fuel and it flowed out of the bowl overflow line just like when I parked it. Imagine that.  First order of business clean the bowl out, drop the float and flush it all out. 
Got the 44mm CV to hold gas. Next I popped a 3/32 hole in the butterfly, got it hot,  adjusted the idle and now I can kill it by adjusting the idle mix screw in. Thanks JW!

Wiped her down some, no more tweaking until I get fresh fuel. Man I have missed the sound of a good sized shovel barking through a Thunderheader.



Thanks all.
Mark

[attach=0,msg1304218]

[Hossamania]

Yeah, you missed it, didn't you?

[jls 64]

Really nice scott.congrats

[Burnout]

That particular Thunderheader is one of the "all time best" pipes made for power and drive-ability. Very desirable.

You might find a pipe that makes a little more power up top, but you will give up a butt load on the bottom.

[76shuvlinoff]

That particular Thunderheader is one of the "all time best" pipes made for power and drive-ability. Very desirable.

You might find a pipe that makes a little more power up top, but you will give up a butt load on the bottom.

It's showing it's age these days. I don't like the idea but it may end up BBQ black in a year or two.

[76shuvlinoff]

Yeah, you missed it, didn't you?

I sure did. I'm thinking one of these rainy days the 3 degree neck cups are going to come out and maybe the chimps too.  I'll likely keep the late front end if only for the brakes.