I bought a carb that was suppose to be already tuned.
the bike blows some black smoke when idling sometimes but not when RPM are up.
Also when riding it's somewhat missing and hiccups.
Is their a basic setting on air fuel adjustments..
I haven't touched it since I installed it

 

Useful information as we do not know what you have:

1. Year of your motorcycle.
2. Model of your motorcycle.
3. Changes you have made or modifications to your motorcycle.
4. Stock exhaust system? If not name of exhaust system.
5. Name of carb you bought.
6. Did yo replace any seals etc when installing the new to you carb?
7. What was it tuned to? Jet sizes etc?

 

Without the above information, no one knows what you are dealing with....

So we couldn't even guess, let alone give an informed suggestion....

 

Ok.I just bought this bike about month ago 1998 Heritage softail classic 1340 CC As much as drivetrain.goes.It's stock.only thing I did is replace starter And Jack shaft oh and this carb (after market )
so the place I bought it said it was tuned already..It is the correct type carb for that bike.The other one would run the bike but you had to keep throttle up and it was streaming fuel out of the bowl through the little plastic over flow tub.
This one idles the bike but just runs choppy.and some black smoke comes out exhaust.. pipes are chalky black soot inside.
So just trying to figure out a good adjustment
Yes I replaced seals on carb..It's just a CV carb from eBay..

 

I’m suspecting that you bought a chinese clone cv carb. You can never tell what the real size of jets they use in them. My recommendation is get a mikuni hsr-42 for your bike. Easy on the adjustments (comes with instructions) and your motor will be more than happy. Worth every penny they cost.

 

They would have absolutely no way of knowing that unless you sent them every detail of your bike. And even then it would only be a starting point.

that like likely a faulty valve. HD part number 27886-78A

black smoke indicates unburnt fuel, likely a really Rich condition.
​​​​​​​
​​​​​​​CV40’s have 2 main adjustment points, jets, idle and main, and air/fuel mixture screw. This is not taking into account the obvious idle screw and manipulating the needle. A good starting point for the air/mixture screw is 2 1/2 turns from the fully seated poisition. On that aftermarket CV40 without a picture we wont know for sure if your adjustment screw is accessible or not. A lot of factory hd cv40’s required that screw be drilled out as it wasn’t readily accessible. If possible pull your bowl and check the jets. Your bike from the factory came with hd main jet 27114-88 and hd pilot/slow jet 27171-89.

​​​​​​​hope this helps
​​​​​​​

 

Ok I located the fuel air adjustment screw.I turned and seated it.
I noticed with bike running and screw seat all way in. It was still running and not really stumbling. Very strange. any ways I turned the screw out 1 1/2 turns It was set at 2 3/4 to see if it would lean the mixture..bike still ran little jerky so after 3 miles I rode home let bike cool and checked plugs again..
They were carboned up again..
I'll try turning it to just 3/4 out tomorrow clean plugs and take it on ride then check plugs again ..
Begining to think this carb is junk..
I still have the Harley Davidson carb as it says on the side I took off and replaced with this one..
It wasn't idling and had gas coming out of over flow tube.
I noticed the spark plugs say Harley Davidson on them too..Original Equipment??

 

I've heard good and bad about the Chinese clones of the CV40 carb..... Not sure I would want one though....

I have had the previous Keihin carb, the butterfly carb on my shovel heads. I immediately switched them for something else.

I have a Keihin CV40 on my 2001 Springer, and like it much more than its predecessor. I think the bad rap of the butterfly carbs has followed the Keihin name, and been unfairly applied to the CV40 also.

I find the CV40 to be easy to tune, and to rebuild. It has performed really well. I believe they will handle up to about 110 HP...

Anyways, here are some tutorials for the CV40. They should apply to the clone CV40 carbs too. You could also buy quality jets and other parts from them, and they should fit the clones... If not, I would trash the clone and buy a good condition, used CV40 off eBay...

https://cv-performance.com/instructions-guides

 

If it was me, I’m only speaking for what I would do. I would return the ebay carb and rebuild the original factory hd one since you have it. It will also have the air mixture screw, it just may not be visible until you drill it. A quick search on the forum will show its been done many times. James gaskets make a really nice rebuild kit, it comes with a new valve, which I suspect is the problem with your factory carb, along with the accelerator pump diaphragm and just about all the gaskets you’ll need. HD still sells your original jets, should they need replacing.

 

If the bike still runs with the mixture screw turned all the way in, your pilot jet, and/or needle are way too rich.....

There should be a good tuning guide on the CV Performance website I posted above...

If you still have the OEM carb, it will be a Keihin CV40. They went to the CV40 on all big twins in '89 or '90.... I forget... In '98, it should have the better version of the CV40 carb with an accelerator pump...

Unless the body of that OEM carb is cracked, you can replace almost every other part. I would trash the clone, and do a complete clean-up and rebuild of that OEM CV40, then tune it per the guide on CV Performance.

I don't remember what jets I had on my 80" EVO Heritage, but stock jets on my 2001 88" Twin Cam are 45/190... maybe a little too much for a stock 80"...

Good luck with your carb issues... Keep us posted on your decisions and results...