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2006 Street Glide Carb Question

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Scrappy Jack

New Member
I'm looking for advise, I'm stumped! I have a 2006 Street Glide with a CV40 carb on it. Jet sizes are 190 main and 48 pilot. Exhaust is stock with thunder slip on's. Air filter is K&N. Everything else is stock. I'm running the bike at 5000 to 7500 ft. I've cleaned carb, inspected all components, adjusted choke cable, and tried about every setting possible on the mixture screw. I still can't get the bike to quit popping through the exhaust when I let off the throttle. I would think my jets are plenty big enough, but I still seem to be running lean. I pulled the plugs and they both seem ok, light tan to white color and dry. I just don't get it, I can make it a little better with the mixture screw, but still not desirable. I was thinking about installing a Yost kit, but not sure if that will cure the problem. I don't want to waste the money on a kit, and end up with the same problem. I can't imagine that I'd need a bigger pilot jet? Could the MAP sensor be causing the problem? any thoughts?
 
Jetting should be plenty with your setup. Sounds like a lean condition to be sure. Need to check all exhaust connections. That means at the head and all other connections. More times than not it means ordering new gaskets for the head connection and remounting the exhaust starting from front to back and hanging all of it loose and then start tightening from front to back. Also be sure to check manifold connections as well as carb to manifold seal. These can be checked with wd40 while idling. Spray around areas and listen for idle speed increase. You can also use a propane torch by using just propane around the same areas listening for idle increases.

Being the slipons were added, I would check those clamps well. You can use a stick lighter around the exhaust connections while running in a protected area. If the lighter gets blown out......

Welcome aboard!
 
Do you have any baffles in the exhaust? Have you checked the headers to make sure there are no leaks?
 
This could be some unburned gasses in the exhaust igniting, have you tried a change of baffles?
Does it pull strong in 3rd gear? No other problems?
 
Jack Klarich said:
This could be some unburned gasses in the exhaust igniting, have you tried a change of baffles?
Does it pull strong in 3rd gear? No other problems?
Click to expand...

Yeah, it seems to have plenty of power, 3rd gear seems normal, just cracking and popping when I let off the throttle.
 
Has this been going on for awhile or something that started after you added the slipons? Given the altitude you're riding at could this be caused by too much fuel? Have you tried going down on the idle and main jet? How is the idle, and have you recently added anything like throttle cables? You mentioned adjusting the choke cable, which is really an enricher valve. If the end of the enricher is not seated all the way fuel can be introduce into the carb even when the throttle is rolled off.
 
If your plugs are more on the whitish side your running to lean. Check what was suggested by others and check with some Harley shops, normally at the altitude you and I are running rejetting is needed.
 
Good advice already given all around. Decel popping can be a symptom of a lean or rich condition; remember when the throttle is closed, the only fuel in the system is unburned fuel. As has been pointed out, unburned fuel in the system could be ignited in the exhaust causing the decel pop.

Conversley, an exhaust or intake leak could be causing a lean condition and the decel popping as well.

As has been pointed out, it is important to know if the decel popping is new and perhaps the result of a recent modification, i.e., new slipons, a change in jetting, etc. If there was no decel popping with the 190/48 jetting, then the jetting is not the problem.

The fact that you cannot eliminate the popping with the A/F screw tells me that something else is going on. As others have suggested, check for intake and exhaust leaks as has been suggested, particularly at the intake and exhaust flanges. Pull the slipons and apply some hi-temp RTV silicone to seal the slipon/head pipe connection. However, before you do that, set the A/F screw where the engine idles the smoothest which should also be the place where the decel popping is minimized; then start checking for intake/exhaust leaks.

I have been down the Yost kit road; don't waste your money as I doubt that the carb is the problem. Additionally, I have dyno sheets showing that the CV carb, with OEM components will out perform a Yost kitted CV; personal experience with my all bore 107 (122TQ/110HP). Additionally, the CV will deliver better mileage than a Yost kitted CV.

A friend recently brought me his 2010 Fatboy which had developed decel popping. Took a look and one of the exhaust flange nuts was missing. Replaced the nut and problem solved.:s
 
Fiddled with it again today for a bit. Tried a 45 pilot jet and a 185 main, the bike would hardly run. Tried a 185 main and 48 pilot, and exhaust popping was worse. Tried everything from almost seated to 3 turns out. The 190 and 48 setup seem to be the best performing, but still popping a little, not as much as the smaller jets. Spoke with the guy that used to own it, he said it did the same thing in Texas at 1500 ft. Checked intake and carb boot with WD-40, no change. Checked exhaust and found no leaks except for one 4 to 5 inches from the end of the slip on Thunderheader. It's at the cap piece that is tack welded on after the baffle. I think it's just for looks. Also, the idle seems to stumble, I can't seem to get it to find a happy spot, I noticed today that it would sit there and idle really rough at around 1000 rpm, then drop on its own to around 800 rpm and run pretty smooth for a few seconds, then jump back up to 1000 and stumble. I'd then crack the throttle, let off and bang pop crack! then searching for idle again. Shouldn't the mixture screw effect the idle? in my case, the idle never seems to change when I go in or out with the mixture screw.
 
It sure sounds like an intake leak to me. Did you check the MAP sensor seal when using the WD40? The MAP sensor sits on top the intake manifold and has a rubber seal around it. Be sure to spray it while its running. Have you checked the float height? The idle mixture circuit may have an obstruction. Looking at the venturi of the carb. there is two small holes at the bottom. The one on the left is the idle mixture circuit. If you disassemble the carb with jets out, spray cleaner through this port. If you got it apart spray cleaner through all ports. With the service manual it will walk you through checking float height.

Any exhaust leak at all is going to exacerbate the issue.
 
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