My carbed '06 RK has had popping upon deceleration (under load/engine braking) since I bought it.Previous/original owner said it always did it since the "Stage I".Bike has V&H round slip- ons,the air filter says H-D,but looks like a K&N,slow jet is .048,main jet is .180,and the mixture screw plug has been removed-indicating someone has in fact "been in there" befor me.Bike runs really smooth,aside from the (annoying) popping and occasional cough from a quick blip of throttle.
So,I went to local Indy to get a CV .190 main jet.Jet doesn't fit the emulsion tube that's in the carb. now.He tells me that most of the time,the dealers don't even mess w/the main jet when doing the Stage I.But out of his assortment of jets,they all have a more coarse of a thread AND larger thread diameter than what I have.
So now I'm assuming that the main jet and emulsifier tube I have are an aftermarket of some sorts...as it is a smaller diameter and finer thread than stock.Just trying to lessen or even rid the popping.BTW,I checked for vacuum leaks and even changed the intake seals-same results.

 

More importantly, check for an exhaust leak. Either at the head, or where he muffler joins the head pipe. Anywhere the exhaust can take in fresh air is a possibility for an exhaust ignition (backfire) if your bike coughs on a throttle blip, you are still on the edge of lean. You didn't mention adjusting the clip on the needle. Also, a sportster needle is a better choice if you are going back in to it. The 48 pilot jet should be enough, I think the next step up is a 50 and would likely be too fat.

 

Can't find any exhaust leaks.Don't know about the needle.It was suggested for me to go up on the main from .180 to .190..........

 

A throttle blip cough from idle speed is usually an indication of a mismatch in the transition from the pilot jet to the main. I'm not saying you don't need a larger main jet, but it sounds like your transition is off, and a larger main may aggravate that further. At the very least, try moving the clip on the needle, but the fix all trick for these seems to lie in the sportster needle. It has a different taper and gives a better transition off of the pilot jet.

 

Main jet size has nothing to do with what you describe IMHO. You can either mess around with this for ages, or talk nicely to your indy to sort it out! Chasing carb burps and farts is either something you can do without asking us, or you need an expert. Your indy can probably give you back a sweet running bike after a couple of hours of digging around in his bucket of carb spares.

 

Think of your carb as having 3 modes.

Idle
Low speed
Mid/high speed

If your bike idles good, then your air bleed screw is adjusted correctly.

But when you transition off of idle, you then start using your pilot jet. It sounds like your pilot jet is well matched to your setup. Again, not talking about a quick blip, just easing off from a stop. You should have a smooth transition.

Once you get moving, say over 1500-2000 rpm, you move to your main jet. If your bike isn't bucking and jumping, blowing black smoke or losing power, your main is probably close. If you like, a 190 probably won't hurt, but again, it's the transition that is at fault here. What you are trying to accomplish is to provide a reasonably consistent amount of fuel through the rpm range. What controls the transition? The needle. Also, have a look at the squirter. Make sure it's actually 'squirting' when you twist the throttle.

 

1988 Sportster needle has a different taper because it did not have an accelerator pump. This needle always gave me good results when tuning a stock carb. Your 48 slow jet should be just about right for your set up.

Bill

 

Bike runs fine-idles nice,takes off nice.It's just when decelerating in gear from a roll (ex:coming off hiway,slowing down from 50 mph. for stop,etc.) getting popping.Also was mentioned to me that popping is kind of common with these kind of (slip-on) mufflers.

 

Any sort of noise in the exhaust is an indication that something is not quite right! On modern bikes, which may be why 'these kind' of mufflers are accused, owners are routinely changing things like airboxes and not correcting the air/fuel ratio. Hopefully by the time we have shaken this problem out you will be pop-free!

 

Also,the right pipe at the outlet is dark,left pipe is tan.Plugs are extremely clean.