Misty cv40

Just installed a cv40 on my '78 80"er. The darn thing idles great and seems to run good, but it kicks out this mist that after about 1/2 hour riding starts dripping out of the air cleaner. Any thoughts where I should start to look?

Not really sure what it came off of but I've got it at 45/175 right now. Right now it's set about 1/2 turn out. If I close it all the way it will stumble but not stall.

check out this site on cv tuning
Harley Davidson Performance

hello...

The CV 40 is a fine carb, and a bigger one(The 44) in a stock application will more likely hurt mileage and performance. it is a common error that newbie make, Bigger is better, so a bigger carb means it will run better, it just means the engine will need to suck in more to keep the same runability. Without that adapter ring, there's no way to bolt the carb to the motor, so I don't see the value of such a test. No, I never tried making mods to it.

Cheers!!
Anthony

Hey there Timstoy.
I have a similar issue with my 02 FLHT. I have a Ness air cleaner and some aftermarket slip-on’s that came with the bike.
If this is fuel were talking about, did you change anything other than the carb? Maybe an exhaust or intake change? The only reason I ask is that what you are experiencing may be somewhat normal. Fuel vapor/ MIST hovering around just outside the carburetor throat is a phenomenon called “Fuel Standoff”. Depending on the (set-up) of the engine and exhaust system, this may be unavoidable. The air rushing through your carburetor reaches extremely high velocity; when the intake valve closes, this air actually bounces back out of the carb due to the intake run being so short. Then, the next intake valve opens and the fuel/air mix is sucked back in again. This happens several times a second and produces that MIST of fuel outside the carb. Air rushing past and through your air filter blows some of this mist away and it collects on the inside of the filter and eventually drips out…
I was pulling my hair out trying to figure this problem out with my bike; in the process I ran across a few good links on the subject. The first two are youtube links and one is of a sportster on a dyno. The other is an F1 engine on a dyno. These are really cool videos and I encourage people to check these things out. The last link is a more in depth explanation of fuel standoff for anyone who wants to go a little more technical.
Hope you all enjoy the videos…
Regards….
Harley Sportster - YouTube
Renault F1 Engine - YouTube
Fuel standoff • Speed Talk

Could very well be "fuel standoff"....with your idle mix only 1/2 turn out would mean you need a smaller pilot jet,a 44 might be the one... if you can get the idle mix screw between 1 and 3 turns out then you have the right pilot jet...

Thanks all! I was sick for a couple days so I didn't get back. Pulled the carb off and the sticker on it says 27489-92. Does that make it a 92 model? Anyhow, I tore into it and found that the o-ring on the idle adjustment was torn apart so maybe that had something to do with it. I'll go ahead and do rebuild.

Hey Copter, those videos are cool. My 'mist' is deffinetly coming out and not hovering. Seems like years ago while running a SU on a shovel I had that cloud effect. It didn't build up enough on the air cleaner to be a problem tho. That bike was a runner! I'll keep plugging away on this.

Hey Timstoy,

The mist comes out of my carb as well. It only seems to do it during BIG throttle movements though. With the filter off, if you blip the throttle hard, a good size fog blows out for a second or so. If you roll up slow, it doesn’t seem to do it as much. If I pin the throttle hard while riding (getting on the freeway or something) I can smell fuel pretty good for a few seconds after. It’s never built up enough to drip out, but that might just be due to the open design of the “Big Sucker” filter. The bike has done this since I bought it about a year and a half ago. I’ve gone through three different main jets, three different primary jets, three different emulsion tubes (main jet holders if you will), and three different needles and a new needle jet. I have also installed a new STOCK slide assembly, (NO DRILLED HOLE) and a stock slide return spring. Nothing, and I mean nothing has changed the mist coming out at all. My main goal in all my testing was to try to get my MPG up over 34, (FAILED), but in the process I’ve been checking the mist as well and it has never changed. The cams have even been changed and had no effect on it. I had an inner cam bearing fail two weeks after I bought the bike and I had to replace both cams. I did go back with used stock cams ( FREE ), only because I just could not afford any upgrades at the time. I have pretty much given up and just live with it for now. I’m still suspect of the CHEEP mufflers it has on it though. It almost has to be just the way the mufflers and the carb work together. I don’t think an ignition timing problem could do this; it would run funky, but don’t see how the fuel vapor would spray out. Another thought is possibly an intake valve not closing all the way or sticking a little, but the bike runs too good and I would think it would POP back through the carb if that were the case. I know the CAM TIMING is right, I installed them myself, and again, the bike runs too good to have a cam gear off by one tooth. I’ve also done the stock header mod; where you grind out the little tab of pipe that hangs down into the exhaust flow coming from the front cylinder. No change at all… So, until I can afford a 2 into 1 system or find some stock mufflers to throw on the bike just for testing, I’m kind of done. If you happen to run across the answer that fixes this issue, PLEASE PM me or post it so I may be enlightened. I will do the same for you Sir, if I figure it out.
Take care and good luck to you….

Thanks again all. I'll let ya all know what happens. I like this carb too much to give up on it.

Any update on this?