If I may add...some of the "free flowing" mufflers like the screamin eagles (and cycle shacks, or any of the shorter type of after market free flowing mufflers) will be more prone to a little decel pop or "burble".

If you get them tuned to a burble and no longer "popping" then you are doing good and damn close to correct jetting. It's just the nature of the beast with the shorter and freer flowing mufflers. They suck in oxygen (air) on reversion which is a key component (air-oxygen) in making them pop.

Just try to tune to a burble and call it good. Don't over jet to compensate. Read your plugs and track your mileage to determine if over jetting.

 

Right on Yankee Dog. Someone else mentioned that the Screamin' Eagle exhaust I have is adjustable. I'll need to spend some time learning about this. The popping is very mild/slight and only happens when decelerating from higher RPM's.

 

Yes, I have cycle shacks (cycle shack used to make the original screamin eagle mufflers) and had the problem on my bike when the engine was stock. I had three issues: jetting, leaky intake manifold seals, and a leak in the crossover tube in my factory head pipes.

Discovered the exhaust leak in the crossover at that little round sealing ring that is supposed to seal the crossover tubes together where they meet. Only when I took things apart to do a cam and top end did I find the soot from that one. The black heat shields on that little cross over tube hid the soot build up from the leak.

With my cam and other slight mods listed in my profile, I am currently running a 45 slow, and a 190 main. CVP velocity needle, screamin eagle AC, Ultima ignition programmed to the dynatek 2000 curve #2. Before my engine work I was a 48 slow, 180 main, and Ultima curve #3, CVP velocity needle and the same screamin eagle AC. I get better mileage with my current set up than I did with my stocker.

It just gives me a kitten purr burble during the conditions you described whereas I was popping in the same conditions as yours before fixing those issues. Good luck with the problem solving.

 

Thanks for your comments. Both emulsion tubes had the 8 holes, only difference between the two was they were in a slightly different pattern. The needle I removed was a CP one with no clip, so it was not adjustable. When I measured the needles there was a difference as I noted in my last post, so I'm going to assume that one was for the non accelerator pump bikes, which would enrichen the 1/4- 3/4 throttle range that the needle operates in. In reality it likely made the pilot jet to 1/4 throttle transition a bit rich as well. I've had more luck on other bikes with CV Carbs, keeping the needle stock and going one size up on the pilot. I think the 45 pilot will work fine, not sure about the main, as I think with the stock exhaust it might be a bit rich. Seeing as the main only really comes into play at WOT, I'll have to wait until I can test it on the road. Time will tell.

I have a lot of experience in CV Carbs, but Bings that are fit on a BMW Airhead. They don't have an accelerator pump, but the bike is air cooled and suffers the same as the Harley when jetting is off. I always found that on the stock BMW Airheads, 1000 cc bikes, two carbs, that they ran much better with a one size larger pilot, which in their case was a 45 pilot. Stock mains seemed to work fine so I always left them alone. I tried richening the main on these bikes, but always reverted back to stock. One thing I have found over the years that going one size up on the pilot jet, affects the whole tuning range of the carb. It will also affect WOT, as the pilot circuit never really shuts off, but continues to add its small percentage of fuel to the total amount. Everything works together in a carb and each area affects the total running of the engine.

The accelerator pump on the Harley carb is a really big plus in my mind, and really helps with drive ability.

 

Well like an idiot I figured out my problem. It was the rubber gasket between the carb and the intake. I replaced the original one on the bike with the one from the carb kit. I thought at the time that it was a bit soft and didn't have the same thickness but the carb went into place and stayed in place while I put the rest of the breather stuff back on the bike, so I figured it was fine. I had ridden the bike back and forth from the tire shop yesterday as I had them put a new rear tire on the bike. The bike still didn't run right and showed a lean condition at the low end, and I figured that's not possible with the larger jets, had good acceleration but stumbled at the low end. I was having trouble getting a good idle and it would run with the pilot screw all the way in. So last night I took the carb off again, put the 42 pilot back in and put the old gasket back in the bike. I checked the plugs and they showed wet, which made sense with idling and accelerator pump using. Put the old dry plugs back in. Started the bike up and played with the pilot screw a bit and got a good idle at 1000 rpm, at around 2 1/8 turns out. Which puts it in the ball park for the proper pilot jet. So hopefully !!!

So sometime today I'll take the bike for a ride and see if all is well. When I think back, when I took the loud fishtail pipes off the bike and put the stock ones on, I rejetted the carb back to the stock settings to set a baseline with the stock exhaust. During that process I also changed that rubber gasket. All my issues started after that. It was strange because it would sit and idle fine, go down the road fine and then every once and a while it would act up. So it turned out to be an intake leak. Lesson learned and I know how to check for intake leaks. So hopefully I'm on the upside. Live & learn.

 

Further update. I've got the bike back to stock jetting 42 pilot and 175 main, mixture screw is about 2 1/4 turns out. I also replaced the old ignition system that had also been causing me some grief. I couldn't be happier with how the bike runs. Less vibration, smooth acceleration. It's quite happy to cruise along at 40 mph in 3rd, crack the throttle and it just picks up and goes. No surging, etc. With the elevation I live and ride at, the 45 pilot was just too rich for this bike.

I bought this bike used and it is certainly no power house, but at my age it suits my style of riding. I've been slowing getting things sorted on the bike, to make it a reliable ride. So onto the next thing.

 

Further update on jetting. Well I recently went on a 1000 mile trip into British Columbia, lots of slower 2 lane traffic and twisty roads so a lot of times you could only average about 50 mph. Elevation changes, up/down, anywhere from about 2000-5000 feet. Bike ran well. When I checked my gas mileage I averaged 62 + mpg ( to the Canadian gallon or about 52 for the US Gallon ) for the entire trip. For one portion of the trip of close to 200 miles I got 68 mpg ( Canadian gallon ). In riding in the mountains I always get much better gas mileage than I do in normal flat line riding out of the mountains, so these averages are certainly higher than normal. Engine never ran hot, but I figured it was running on the edge of being lean, once and a while when coming down to a stop and idling.. So when I got back I put the 45/180 combination back into the carb. Engine runs maybe a bit smoother, still doing some road tests to get the mixture screw right for an good idle.

At present the only really difference I can tell between the two jetting pairs is it runs a bit smoother when hot. Engine is totally stock, so performance wise no real difference in the get up and go department. I likely don't need the main at 180 as I'm never at WOT but seeing as I was into the carb again I changed it as well. I would think the slightly richer mixture would lower the cylinder head temps a bit and that is not a bad thing on an air cooled engine.

I'll see how it all works with cold choke starts and idle. The EVO engine is not the smoothest running so not always easy to get the idle right as I like to stay at 1000 rpm, for oiling purposes.

 

Well another update. I'm back to the stock jetting, 42/175. For whatever reason I couldn't get the 45/180 combination to work in my bike. Maybe its the altitude. Bike is still totally stock, exhaust & intake. I post this update, just to show what I'm doing and to potentially help others that are having jetting issues. I'm not expert, and this is just to record what I've done.

No matter what I tried I couldn't get a decent idle and with the choke ( I know not a real choke but an enrichner ) on a cold start it would run too rich ( you could smell it in the exhaust ) and it was hard to keep the engine running no matter where the choke was set. When off choke and fully warmed up you could turn the mixture screw over a wide range with no affect on idle. All this indicated to me bike was running too rich. That's not to say the bike didn't run because it ran fairly well at other areas but gas mileage dropped.

So when I put the stock jetting back in the carb, I put back in the sportster needle that I had with the stock 42/175 jets.. I set the mixture screw at 2 turns out for an initial setting. Buttoned the carb back up and went for an hour ride. Now when I turn the mixture screw something happens, and it affects the idle. I still haven't got the perfect setting for the mixture screw ( if that is ever possible with a carbed bike and variables like temp, humidity etc ) but I'm getting close. If you've every followed Joe Minton ( American Thunder and wrote the book on tuning Mikuni carbs ) this set up is what he recommends for evo & 88 twin cams ( stock jetting, 88/89 Sportster needle, richen the mixture screw 1/2 to 1 1/2 turns out ). Now the mufflers are a lighter shade of gray with the stock jetting, another indicator it was running too rich with the 45/180 combination. My method when setting the mixture screw is to take the bike for a ride, and approx every 15 minutes pull over, check the idle at a stop. If it has gone up since the last stop, I know the bike is running too lean. Blip the throttle, if no farts or burps, then I turn the mixture screw out a bit, one click on the spring ( you can feel it on your fingers with the bike running ) from my initial 2 turn setting, adjust the idle back to 1000 rpm. Go for another ride and so on. Bike pulls fine, no hesitation etc.

So for the record, bike is totally stock, I live at approx 2700 feet of altitude and all of my riding is between approx 2000 - 5000 feet.

 

cycleman11: if you are still having issues with irregular idle speed after all that you might want to look for an intake leak. (you can start a new thread asking for help rather than highjacking this one ).

My update is: I finally got all my parts I ordered for the upgrades I'm planning for my bike. It took several WEEKS for my adjustable pushrods. According to USPS there was an issue with the railroad in California that delayed delivery. Now I'm waiting on some 'non-riding' weather to tear into her.

I believe I can actually hear an exhaust leak behind the rear cylinder coming from the crossover tube just like Yankee Dog said he found on his. I've got new gaskets for this. It will be resolved when I do the upgrades.

Stay safe. be well.

 

I've checked and no intake leaks. The evo engine is not the smoothest running beast, so getting what is called a smooth idle is a bit hard to define.

One thing I would like to know is what Harley sets the mixture screw at before they plug it. This is for a stock late model evo, stock jetting, pipes etc just as it rolled off the assembly line. I've looked on many forums, sites etc and can only find one reference that says that it is set to 1/2 turn out from the factory. There is no end of information on richer jetting but I'm just looking for information on stock bikes. One always needs a baseline. As a point of interest I'm currently at approx 1 1/8 turn out on the mixture screw, stock jetting and sportster needle. Bike idles pretty good at 1000 rpm when hot. No bogs, hesitation etc, so I may just leave it be. I may just post this question on the forum to see if I can get an answer.

As a comparison not a HD carb, but on a Bing 40 mm CV carb with no accelerator pump, the factory setting is 1 1/4 turns out. In my experience with those carbs they only require the width of the screwdriver blade, turn in either direction to get it spot on. A very small adjustment. So my current setting on the HD carb of 1 1/8 is not far off. The stock Bing carb runs a 45 pilot and 160 main. The richer pilot takes care of the lower end where the HD accelerator pump works. There are also some differences in the slide spring and the Bing has a larger diaphragm as the bing slide needs to be more sensitive and pulls easier than the HD with the accelerator pump. I actually prefer the accelerator pump, makes things much better just off idle.

When talking carbs, it would be really nice to see some actual Air Fuel Ratios at idle, 1/4 throttle and cruising area, for stock carbs with stock jetting and also after richer jetting, using some form of electronic sensor. Stoic is 14.7:1 AFR and max power is developed at about 13.5 AFR. Anything richer than 13.5 AFR offers no advantages to a street bike. So ideally you would be trying to get the lower end of the carb in the richer area, but when cruising down the highway you don't need that mixture, and something closer to Stoic is better for the engine.Just throwing bigger jets into a carb doesn't solve much. Often the extra fuel just washes the cylinder walls and doesn't allow the engine to get up to proper temperature as the excess fuel has a cooling affect on combustion. I think the expression " Show me the Money" comes to mind.

Sorry got long winded again. Much easier to discuss in person.