CV40 jet sizes

[1340evo]

Wish someone in the UK had CV bits to do this on a dyno.
May have to invest in a sensor kit for the front pipe and do it myself...

[JW113]

Why not? I don't know what dyno tunes are in the UK, but here in the USA, you can buy an AFR and roll your own for less than a dyno tune. I have a Daytona Sensors, but I saw this one and thought it was pretty cool, not to mention, very affordable:

https://www.safrtool.com/shopping/viewSAFR.asp?pid=1

-JW

[1340evo]

That could do with some pictures but guess I see how it works. Or just drill and weld on a senso bush... will have a look ans see whats about

[JW113]

That's what I do, weld a bung in the pipe. All depends how much you fancy style and aesthetics.
 

-JW

[1340evo]

I have V&H pipes so thet come with a cover to the front, not sure you'd see a bung on the back that much, and obviously plugged when not in use. We have expert welders at work also so would look like it's meant to be there

[1340evo]

Update on this post having found a bit of time and fitted a AFR.

so started testing last week and was shocked to find it very lean almost everywhere! When you rode the bike and brought it home, youd hear a tink, tink, tink, sound from the exhaust as it cooled down. Having messed with it for a week its not making that sound now so guess it running a tad cooler. So this is what I found :-

7.7.22 45 / 180 2.5 turns N65c No shim   Runs way lean most places, seeing some 16.5's under load!
8.7.22 45 / 180 2.5 turns N65c .030shim  Runs better, still lean at top and acceleration, constant 13.5, top 14.5
9.7.22 45 / 190 2.5 turns N65c .030shim  12.7 tickover, 1/8 turn 15's, WOT 14 through range
15.7.22 46 / 190 2.5 turns N65c .030shim... still to test

So will work on the bottom end and getting that right as it impacts to top end also. Acceleration is where it leans out a lot?.. looks like I'm heading back to 48 / 190 at least ....

[JW113]

I don't know if there is a right way or wrong way, but here is what I do.

Take a AFR baseline of idle, steady cruise in 3rd gear at 40mph, steady cruise in 5th gear at 70mph, and WFO in 4th gear from 40mph to 80mph.

Idle is set with the idle screw of course, and shoot for around 12.8.

The two steady cruise readings are about economy/mileage, and you want somewhere above 13.8 or even in to the low/mid 14s. I shoot for 14.4. This is mostly managed with the pilot jet, especially the 3rd/40mph reading, the 5th/70mph reading is by the needle & shims but also the pilot jet. It gets to be a bit of an aggravating balancing act.

Full throttle is where you really need to be concerned, as at idle and cruise, running lean is not so much a big deal as the amount of heat (from the fuel) being created is far less than at WOT. Here you need to be at the very least below 13.0, and closer to 12.5. Running lean at WOT creates a lot of heat, can be dangerous for the engine. Main jet, along with shimming the needle, will dial that in.

I, like you, was shocked the first time I hooked up an AFR gauge and saw how lean the thing was, especially on my Shovelhead. Due to the lousy combustion chamber design, they require a hell of a lot more fuel than an Evo or TC. After spending some time on both Shovelhead and Ironhead to get the AFR tuned correctly, it is simply amazing how much better they run. Need to get around to doing the same to my Evo, I have no doubt what-so-ever that it is lean as hell. My TC 'King was tuned on a dyno so I suppose it's close, but might as well do that one also someday.

-JW

[kd]

I will add that having 3 circuits controlling low mid and high rpm influenced by manifold pressure (vacuum) I have found it best to keep the influence of each circuit close to the next.  By that I mean too large of a step to the next circuit will cause running issues like stumbling or bogging.

[1340evo]

I don't know if there is a right way or wrong way, but here is what I do.

Take a AFR baseline of idle, steady cruise in 3rd gear at 40mph, steady cruise in 5th gear at 70mph, and WFO in 4th gear from 40mph to 80mph.

Idle is set with the idle screw of course, and shoot for around 12.8.

The two steady cruise readings are about economy/mileage, and you want somewhere above 13.8 or even in to the low/mid 14s. I shoot for 14.4. This is mostly managed with the pilot jet, especially the 3rd/40mph reading, the 5th/70mph reading is by the needle & shims but also the pilot jet. It gets to be a bit of an aggravating balancing act.

Full throttle is where you really need to be concerned, as at idle and cruise, running lean is not so much a big deal as the amount of heat (from the fuel) being created is far less than at WOT. Here you need to be at the very least below 13.0, and closer to 12.5. Running lean at WOT creates a lot of heat, can be dangerous for the engine. Main jet, along with shimming the needle, will dial that in.

I, like you, was shocked the first time I hooked up an AFR gauge and saw how lean the thing was, especially on my Shovelhead. Due to the lousy combustion chamber design, they require a hell of a lot more fuel than an Evo or TC. After spending some time on both Shovelhead and Ironhead to get the AFR tuned correctly, it is simply amazing how much better they run. Need to get around to doing the same to my Evo, I have no doubt what-so-ever that it is lean as hell. My TC 'King was tuned on a dyno so I suppose it's close, but might as well do that one also someday.

-JW

Thanks, thats great info indeed, I'll print it off and take it with me to make notes. Problem is trying to remember everything after a run, If you just target a couple at a time and go from there I guess.

When I initialy set the bike up seat of pants I was at 190 / 48 and a .030 shim, but allowed myself to be talked down to the smaller jets. But having put the AFR on there, I didn't think it was working right, but its amazing how 185 to 190 changes the AFR a lot.

Also, a lot of people are quoting 12.5's to 12.9's, Its good to see you saying 14's in places as I know now I'd be going too big.

On WOT from to to bottom of the rev range its bouncing around the 14 mark which by changing the low jet may now be addressed, but I'll follow what you say and see how I go.

Where it does go lean now is by just opening the throttle a tad at any speed so need to sort that one, but will do as you say above 

One question I have. when setting or chosing the pilot jet, do you take any pre-set gap from the butterfly? I've tried to follow instruction on setting this before but its never worked, but there again, the idle is set on the butterfly screw right? so to get the bike to stall etc on the air screw, do you have to back this gap off???

[1340evo]

I will add that having 3 circuits controlling low mid and high rpm influenced by manifold pressure (vacuum) I have found it best to keep the influence of each circuit close to the next.  By that I mean too large of a step to the next circuit will cause running issues like stumbling or bogging.

Yes, was reading today some guy who's set the bike up and had a 42 slow running and a 195 main and thinking that can't just be right. As you say, things have go to work together 

[JW113]

Try to keep in mind where the fuel is getting into the engine at different throttle settings.

Idle: From the idle port. Primarily controlled by the idle mixture screw, at far back of carb on the bottom side.

Steady cruise: From the transfer ports just under the throttle place at very low throttle positions 90 to 1/8), along with the main port at higher throttle positions (1/8 to 1/4). Controlled primarily by the pilot jet at low throttle, and the needle at higher.

Full Power WOT: From the main port, primarily controlled by the main jet but needle also.

From 1/4 throttle to WOT, it's a balancing act of needle type and shims.

Full power WOT you want to be down around 12.5 for max power.

At cruise, you want to be leaner so's to get reasonable fuel mileage, I shoot for 14.4. As you have found, you can have the motor quite lean, into the 15s or more, and it will still run. But anywhere around stoichiometric (14.7) and higher, the combustion temp gets quite high. At low throttle positions, the motor can likely take it. At WFO, that lean is in the danger zone.

Try not to make more than one carb adjustment at a time, and try not to focus on all the areas of tuning. Get one dialed in, move on to the next. There will be a lot of rechecking and re-tuning along the way, can be kind of frustrating. Think of it as a game.
 

-JW

[1340evo]

Okay, so I did a few test runs as I'm set now but I'd changed from 45 to 46. think thats a bit OTT as at 1 1/4 turns I'm only getting 11.5 where as on the 9th July with my 45 jet at 2 1/2 turns I was getting 12.7 which was about perfect I think....

9.7.22 45 / 190 2.5 turns N65c .030shim  12.7 tickover, 1/8 turn 15's, WOT 14 through range
17.7.22 46 / 190 1 1/4 turns N65c .030shim... 11.5 tickover, 3rd at 40 11.8, 5th at 70 13.8,
4th WOT from 40 to 80  40 12.5 / 60 11.5 / 80 14.5

so from that what would you suggest? maybe the whole thing is no good as my idle was rich so does that screw everything? got to say, reading the numbers on the AFR is not easy as they do jump about a bit.. On most of the above I've done a few runs and these are the figures I think are representative

[turboprop]

Seems you have confirmed the size of the intermediate jet that is needed. Have you considered looking at needles with different profiles?

[speedzter]

Don't forget you really need to check both front and rear cylinders, and average out the Afr between the two.

[JW113]

Damn dude, he'll never get done with this doing that!
 

If this were racing, i.e. drag racing, and for money, sure. For a ride around town bike, waste of time. At least in my opinion. Get one jug tuned within reason, and have fun with it. The other jug's breathing through the same carb so it can't be *that* far off.

As Turbo said, maybe a different needle. I don't really like those N65C needles myself. They have a smaller diameter at the top of the taper to compensate for no accelerator pump, but they were still used in a sportster, so the diameter at the tip is bigger than a big twin.

-JW

[1340evo]

Yup, I'm going to take it the rear jug is okay from doing the front. Looking at the plugs they both look the same so no reason to think it's not getting the same supply from the carb.

I can try needles for sure, but would be guessing as I know little about them and their relation to each other

So for now, I'll go back to 45, and I have a 195 on order to try.

One thing I've reported before, as you just start to open the throttle it does go quite lean from any given RPM at cruse. I guess the carb has to catch up with demand but it appears to take a long time, so is the slide working as it should. I wil check the hole in there to see what size it is

[JW113]

Don't worry about it as you crack the throttle. Yes, will always go lean briefly until the main circuit starts to see "signal", i.e. vacuum, to pull the fuel up. Hence, accelerator pump. Focus more on steady state.

-JW

[turboprop]

CV Needles for Harley CV Carbs.

[1340evo]

Right, tried the 45 / 195 but never got to the top end due to rain
but 70 in 5th is about 14.2
and 40 in 3rd is about 13.5
Tickover back at 12.8 on 2 1/2 turns So that lots good

What I'm still seeing is from just cruising on not a lot of throttle, to just opening a bit more but before it hits the injection pump, it goes very lean for as long as it sits there... say its a flat road and you are doing 50 but want to go a tad faster so you just crack it open a bit and lean it goes until you trottle back, or go further...
its like the pump needs to come in sooner, but even if it did, it would not last after the initial squirt, or the slide need to go up quicker.... Or I accept its a lean area?
Open it a bit more where it hits the pumpa and its fine down at 13's...
Is there anything I can do to improve this area at all? as was thinking of .030 more under the needle but think its a lower rpm where I'm seeing it....

[Hossamania]

Which gear are you in at 50mph?

[1340evo]

4 th i guess, okay may be going a bit slow for the gear, but it will do the same at 50 in 3rd for example if you just twist it that little bit more....
I'm going to shim the needle more but think the issue is before the slide moves anyway?

[turboprop]

Seems you now have the low and high speed jets confirmed as well as the idle mixture screw. All that is left is selecting the correct needle, adjusting its height and maybe playing around with different slide springs and slide ports.

FWI - Most members of this forum will be very quick too chime in with 'Dont drill the slide' but very few of them have ever drilled a slide or tuned a carb with an AFR like you are doing. It is just the nature of online forums. I suggest you get a couple slides and springs and maybe a flat bowl with an adjustable fuel pump.

Adjustable Harley CV Float Bowl.

[Hossamania]

I will admit I have not drilled a slide, and so I should not have recommended or discouraged it without first hand knowledge.
I don't consider 50 mph in 4th gear to be too slow for the gear, that is about the right cruising combo for that speed and gear.

[1340evo]

That adjustable pump looks interesting for sure.. yes, I'll get a new slide and I can play about with the old one... also needles but which way to go there?

[turboprop]

That adjustable pump looks interesting for sure.. yes, I'll get a new slide and I can play about with the old one... also needles but which way to go there?

All four of them.