Because this bike ('92 FLHS) sat for the last five years I had to rebuild the entire fuel and intake system. Got her running good and strong now, just have a little/mild popping on deceleration. Bike came with Screaming Eagle slip on mufflers and someone in the past has tinkered with the carb. The factory Harley CV carb had enough crud on it that I couldn't recognize the numbers on the jets. Does anyone know what the factory jet sizes are for this carb?
Picture is for entertainment purposes only
From factory it had a 40 low, 160 main and N86F needle.
With SE mufflers and stock cam, you need minimum 42/175 jets. But if you're ordering new jets, I'd go 45/175. In any event, 40/160 with that needle is way too lean with those mufflers and likely causing the decel popping.
The last recommendation is probably pretty close for the pilot but the main is a pretty big jump of 2 sizes up. So I would suggest going up just one size on the main. You'll have to try it. The stock main might be fine with your bike. Do some reading on how to determine the correct main jet size as it only really comes into play at wide open throttle. Here's my explanation of jetting.
Jetting to a large extent depends on the elevation where you live & ride. Other things like different exhaust and intake mods will also affect jetting. All bikes from the factory are jetted for sea level so that is always your starting point. With whatever set up you are running on your bike at your general riding location, on a full warmed up engine , as a general rule - If you can kill the motor when you turn the mixture screw ( pilot screw ) all the way in, and you get the best smoothest running engine somewhere between 2-3 turns out from seated position of the mixture screw, then your pilot jet is fine. If you find you are getting decel popping ( and the above is true ) try turning mixture screw out 1/4 turn, before you do anything else. See if that helped.. The pilot screw needs to be adjusted in small increments.
Elevation increases, each 1000 feet above sea level adds about 1 % richness to the pilot & main jet. So say the bike was jetted for 175 main at sea level, then at 3000 feet, then that jet size could drop to the next smaller size. Normally you leave things alone at anything below 5000 feet. I use the example where I live at 2700 feet and often ride into the mountains with elevations in the passes around 4500 feet. With the stock jetting in my bike 98 Electra Glide Classic, stock bike pipes etc, the factory jetting 42 pilot, 175 main is fine. I can't quite get the engine to quit with the pilot turned all the way in but it idles fine at 2 1/4 turns out. Smooth acceleration, no bogs etc. So I leave it alone. When I bought the bike it had aftermarket exhaust, 46 pilot, 185 main. That was way to rich even with the pipes. Put the bike back to stock pipes and went with the stock jetting. Accurate plug reading on ethanol fuel is just about impossible.
Being slightly rich on a bike that you travel with is going to be fine and with carb'd engines, changes in elevation, humidity, temps etc all will affect the running of the engine. One day you go for a ride and it works fine, next day its just a bit off. You learn to live with this as the CV carb can only adjust itself so much. The CV carb is actually pretty good at providing some self adjustment, as the diaphragm ( pulls the needle up ) is affected by changes in air pressure. Often on the newer carb'd bikes the factory jetting was pretty lean but HD for the most part has used the same pilots 40 or 42 ( depending on bike ) for a lot of years. So jetting is a trial & error type of thing. Only change one thing, then go for a ride. If that change didn't work, put it back to where it was and go onto the next step.
A couple of tips. 1.For adjusting the pilot screw is one of those small screwdrivers with 4 flat sides. That way you can easily count how many turns in or out you've done. I've tried the aftermarket mixture adjustment screw, but find it easier for me to use the old screwdriver method. I haven't found an easy way to use a mirror to see the mixture screw up under the carb, and find doing it blind, just counting the sides of the screwdriver work for me. Another tip is that if you don't need the choke/enrichner to do a cold start, then it is jetted too rich. You should need to use the choke, and don't touch the throttle when starting a cold bike as the accelerator pump enters the picture. A fully warmed engine should start and idle at about 1000 rpm with no hiccups. Jetting can be frustrating, and if you find that you can't get it to work, find somebody that can. It will reward you with a good running bike. Good luck.
I had the decel popping after I did the stage 2.
Couldn't tune it out of the CV, Went with a Mikuni 42, it was better.
I had to go with lollipops in the exhaust, that worked.
An update. Out for a 4 hr ride on the weekend and found that the bike was too lean. This was at higher elevations in the 2700 - 3700 ft range. Bike definitely shouldn't have been lean at these heights with the stock jetting, stock exhaust etc. I was surprised that it was lean at the top end as it showed lean symptoms when going up a hill under load and roll off throttle. Also had the classic increase in idle when engine was hot, which too me indicates a lean condition. I had a carb kit for the bike that I'd been meaning to install, so pulled the carb yesterday and replaced everything that was replaceable and gave it a good cleaning. Float bowl has always been clean every time I've had it off the bike. Seeing as I had it all apart, I went one size larger on the pilot and the main, so they are 45/180 now. When I was in the carb I saw that it had an aftermarket needle, looked like the one for non accelerator pump carbs as the first stage was thinner than stock and it had a different taper, which would provide more fuel at the bottom end. Probably explains the burbling I was getting at real small throttle openings. Put stock needle in. Got everything back together and bike started right up, had a backfire through carb so enriched the pilot screw 1/4 turn out. Then as bike warmed up adjusted the idle to stay at 1000 rpm on the bike's tack. Engine ran much smoother and good throttle response, and dropped back to idle quickly. At this stage I'll have to wait until I can go for a ride and see how it all works together.
One thing I should mention., I bought the bike used and at some time in its life it had a used Fireball HI-4E ignition module installed. It looks like it used the stock ignition pickup and then was wired into the system using the stock ignition plug. It was at the mid position # 5 as recommended by the manufacture, but I suspect that the timing was too far advanced. That would help explain my lean condition. I had played with the settings from 1-5 and found that the only one that made much difference was when I used the #1 position. Then you could tell that the timing was retarded. I've ordered a new Dynatek 2000i ignition and coils kit, so I will get the timing sorted and replace all the old used stuff. I would really like to have just used a stock ignition module, but they don't seem to be available new anymore and buying a used one is too much of a gamble. I'll post again once I get for a ride.
The D2ki is a really good ignition and following the instructions, initial timing is simple and accurate. Good call on the 45/180. That will take care of most any open type exhaust as well as stock to most any bolt-in cam.
The aftermarket needle you mention, did it have an e-clip and notches to adjust the height or a head like a nail as the stock? Second question, did you remove the emulsion tube (main jet holder) and notice how may tiny holes were on the side of the tube?
Reason for asking, they're are basically 4 designs of the emulsion tube. Two, including stock, will accept stock main jets, the other 2 won't. So that leaves the one that only has 2 tiny air holes on the side, where the stock original has 8 holes. The super skinny looking needles usually have the adjustable clip and are used with the 2 hole tube.
Point being, if you try to use a stock type needle with the 2 hole aftermarket emulsion tube, it's going to drive you nuts with tuning the carb.
06-10-2022 | 08:05 PM
Harley CV carb
