HarleyTechTalk

OK, so I'm trying to dial in a Keihin CV-40 that I have on my FLH. Just to throw this out there, those of you that are running the CV, what are you using for a main jet?

Now down to the story...

Bike runs great, and I mean really great. As long as I don't give it more than 1/2 throttle! More than that, it makes noise and either holds it's own or loses power if you whack it wide open. Yes, classic way too rich jetting. I get that. I've been using CV carbs for years and years on a bunch of bikes. Always had the main jet in the neighborhood of 185-200. And always works great. I was using a 180 in this FLH, and was having said problems, nothing past 1/2 or even less throttle. Today I put a 165 in and took it for a spin. NO difference. 

They don't make much smaller jets than a 160, which I have, but something tells me that ain't the problem. The needle is a N72R. Should be fine for this application. It has lots of torque and will run 80+ on the freeway, but just don't whack the throttle open or it will complain and likely slow down. The pipes have fairly black soot, so yes indicates too rich. The plugs look fine, which is odd. I made sure the diaphram is good. Also checked the float level, it's dead center .445".

I have a S&S E that I'm considering throwing on just to see what difference it makes, even though I'm not a big fan of S&S carbs. Anyway, running out of ideas. Curious to hear what you guys with CVs have to say.

-JW

  Check the CV Performance web sight, they have some tuning tips there , might find some helpful info .
http://cv-performance.com/harley-cv-carburetor-tuning-issues
 
Any possibility the float is sticking ? Staving the motor with low bowl level . I think I have a 190 & a 200 , both are in Panheads though .

I am no tuner. When I ran a 40mm the main was 190ish but it was on a 93" mill.   It ran "good enough" with great manners, didn't quite have the top end my E had (See -I am no tuner- section again) the trade off was worth it.  My Es were older, did not have the adjustable air bleed. I always ended up with them running a bit rich.

Mark

edit: I had a CV tuning document here somewhere. You know how it is, you will forget so you save something to a computer because paper is old fashioned.  Then you still can't friggin find it. 

edit II: here's a good cv on a shovel thread
http://harleytechtalk.com/htt/index.php/topic,27610.msg280576.html#msg280576

Check that needle jet is not upsidedown, as your symptoms may indicate this.
I've a CV40 on the '04 Road King, which has a 195 or 200 main jet and it runs beautifully.
S&S Super E on the shovel now, works very well with adjustable air bleed and Thunderjet

Quote from: Trouble on February 14, 2016, 04:57:33 AM
Check that needle jet is not upsidedown, as your symptoms may indicate this.
I've a CV40 on the '04 Road King, which has a 195 or 200 main jet and it runs beautifully.
S&S Super E on the shovel now, works very well with adjustable air bleed and Thunderjet

  It could also be missing.  What is the pilot jet size and how is the accelerator pump diaphragm.

One more less obvious, thing. Ensure that the Enricher is truly turning off, it needs to seat securely and leak free on the seat to ensure it is not Enriching itself..Hard think to track down , or tune out if it don't seat properly.

Trouble: "Check that needle jet is not upsidedown"

Doesn't appear to be. IIRC, if you install upside down, the wrong end won't go through the hole in the bottom of the bore.
[attach=0]

AJ: "What is the pilot jet size and how is the accelerator pump diaphragm."

45 pilot jet, and the accel pump squirts when you open the throttle.

Racepres: "Ensure that the Enricher is truly turning off"

The knob seats fully in the closed position, and that right angle bend and nut are tight against the carb body. Other than the obvious from looking at it from the outside, not sure how else it is seated. That said, the bike will not start cold without the enrichener pulled, and after it starts I can vary the RPM or stall the motor by pushing the knob in. So it appears to be doing it's job.

Also note, it runs fine at any throttle position other than 1/2 open or more. Idle is perfect, and low speed part throttle is great. Which means that the idle/pilot circuits are working correctly, and not getting excess fuel if there was a leak from the accel pump or enrichener, or too high float level. Right? It just seems to me like classic too big main jet. Although since the problem shows at 1/2 throttle, the needle/jet are involved as well (which is fed by the main).

Time to pull it apart again and have a close look, and maybe try the S&S E lying in the corner of the garage...

-JW

Well, check that diaphragm again

JW, I assume you have already checked for intake leaks etc.
Hard to tell from the seat but are you pumping black smoke?
Has anyone else possibly molested this carb by drilling out the slide or modifying or "upgrading" the spring to reduce the reaction time?

Mark

My 82 FLH 80" CV has a 190, 45 and the sportster needle. Runs great, 40+ MPG. Stock H cam.

Will check the diaphram.

Mark, this one came off my '04 Road King almost the day I rode it home (and put on a CV44). Bob C used it for a while on his road glide. Ah-Ha!! That's it. BOOOOOOOOOOOOB!!!!

-JW

Quote from: kink04fxd on February 14, 2016, 01:55:48 PM
My 82 FLH 80" CV has a 190, 45 and the sportster needle. Runs great, 40+ MPG. Stock H cam.

Very similar to my 1982 FXE, but had to go to a 48 pilot to improve starting.  V-Thunder SHV 4000, KB 9.5:1, Chrane HI-4E.

2000 Road King + 95" M/M with Harley's VFI copy + closed loop.

Quote from: JW113 on February 14, 2016, 02:08:47 PM
Will check the diaphram.

Mark, this one came off my '04 Road King almost the day I rode it home (and put on a CV44). Bob C used it for a while on his road glide. Ah-Ha!! That's it. BOOOOOOOOOOOOB!!!!

-JW

yep I done wore it out.   lol  It ran great on my 95" hot rod...

I think you've got a timing deficit. (or maybe too much too soon?)   When I rode it it felt like it wanted to be shifted like a diesel.  lol I was in 3rd at 30 mph.  Nothing happens above 3k it just shakes like a dog sh*ttin razor blades and nothing happens.   

Agree. Could be. Took the carb apart, nothing found. Jetted down to a 160 main, no help. It just does not want to rev beyond 3500-ish. And now coughs a lot with the small main jet. For the life of me, this has been the hardest bike to time that I've ever encountered. Cannot believe the timing light. Gonna bump up the timing until it compains, see what happens.

-JW

Had the same problem last spring after I rebuilt a CV40 to put on my 74". Hope you got a solid press on flange. Mine was out on time. Had to sneak up on the throttle to get going. I chased my tail until i used a timing light. Kept cutting grove in timing plate until i realized I was going the wrong way. I have OEM flywheels with the timing marks. Dirty

Fiddle with the static timing, but also diddle with the advance curve in that S&S ignition module...   Maybe slow the curve and advance the static a bit.

Oh... Did you use a VOES?  Cuz if you didn't you should be under advanced.  If you have a switch that says VoES yes/no, guessing No means full advance?   I dunno... just thinkin outloud.

  Throw the S&S on , just to see if its the Carb. causing it.

OK, so with the 45 pilot, 160 main, and N86 needle the thing was more than obviously too lean. Coughing out the carb and took forever to warm up, and with wide open throttle would "slow down" until I backed it off a 1/4 turn.

I put it back to the set up I had originally, 48 pilot, 180 main, N72A needle, but also bumped the timing up quite a bit. It did help, quite a bit in fact. Will take throttle now, but still runs out of  at WFO. And has now developed some other symptoms, like give it throttle and Waaaaaaaaaaaaabupbupbupbup when it winds up. No way I'm into the rev limiter.

Bob, I have the VOES wire grounded, so should be locked into full advance. This S&S Hi4N does not have a selection for no VOES, they say ground it if not installed.

I'd say I have the ignition module about 3/4 of it's full travel to the advance. Was about 1/2 or midrange before. This is killing me, never has so much difficulty timing a motorcycle in my life. Using the timing light, it said midpoint was on the timing mark, but that just can't be right. It ran like crap at that setting.

Also, I noticed that after I advanced it, it ran cooler. Heads measured around 300 or so before, tonight after rejet and timing advance they're around 240. So that points to retarded timing.

Will call my pal Roger tomorrow and get an appointment on the dyno. Need to make some forward progress on this.

-JW

Do you have anything else you can put on for an ignition?

As in points? Sure do. But I had no luck trying to time it with those either.

Ya know, I have this nagging thought in the back of my head that after riding a 130hp twinkie and then getting on this stock 74 cube shovelhead, that's all there is!


-JW

 Yeah, 1/2 throttle on 130HP might feel a little different than 1/2 throttle on the Ol Shovel.

Valid point but it should still run smooth to the top, wherever that is. WFO should not sputter, gag, or fart. 
It's been a lot of years since the factory 74"er was in my frame and maybe I remember it better than it was but as I recall I could tease triple digits. It took a while and "Potty mouth" fell off but that's my story. 

And that is where I think I need to adjust my calibration here. This one will do 80 no problem, and although I've not actually had it up to 100 I'm sure it would answer the call. But like you said, it just won't be in any hurry to do so.

Am now leaning more toward "that's all there is". It pulls fine until too much throttle, and then there just isn't any more. Perhaps around the 1/2 throttle mark the carb's passing all the air that the motor can pull in? Frankly, I'm OK with that. Did not build it to be a hot rod, just a nice old ride-it-anywhere scoot.

At any rate, have a dyno day scheduled when I get back from Seattle after next week so will get it dialed in and after that point, it is what it is.


-JW

JW,
What air filter setup are you running?
Have you tried running w/o filter to see if it loads up?

That just doesn't seem right.  Ok, I know my Shovel's a stroker, but she does 80 with ease.  Anyway, at any speed below top end, I can gear down and wack the throttle and the bike will jump. 
Maybe too much restriction in the pipes?  Didn't you say somewhere back in this thread you've got an S&S sitting on the shelf?  I think I'd stick it on there and give it a shot, just for the knowing.