Erratic Hesitation / Popping

Working on a 2006 Sportster 1200c.

The bike was towed in so I have no reference as to how it was really running before this install. Based on my friend it would barely stay running (which I did test) and it was bad enough to even try taking out on the road. I can say that whoever worked on it last removed the stock backing plate and had the air cleaner element just sitting up against the carb throat.

I installed both the CVP Stage 1 and rebuild kit over the weekend. This went along with a K&N RK-3929 complete Air Filter kit. The bike was running a 180 main and 42 pilot jets. Based on the kit and its application I went with the 185 main and the 46 pilot. Everything else was as per the installation instructions. Entire carb was cleaned and rebuild kit installed along with the EZ-Just mixture screw and new packing kit. The slider has not been drilled.

Problems I'm now having: erratic dead spot / hesitation off idle under load (pulling off from a stop) both at cold & warm engine; I need to really ride the clutch to keep this from happening. Also will get a sporadic single pop through the carb while just cruising at around 35-40-50 mph; not giving any throttle at all, just a "cough", the bike bucks a little and then back to normal. Again, this is either cold or hot. I have adjusted the EZ-Just so many times and nothing makes a difference. Right now I have it set at 3 1/2 turns out. Frustrating part is one time I take the bike out all is well. The next test ride the problems are back.

After much searching of the forum I have run all the different tests I could find; checked for vacuum leaks, swapped out the accelerator pump, double checked the needle jet position, float level, etc.

I will say that ever since installing the kits the bike fires right up. At cold I set the choke, give the throttle one twist and it fires and runs good at idle; no hesitation or coughing when I do a quick snap of the throttle. Once warmed up I don't have to give it any fuel at all to start it, just hit the start switch and it fires and runs.

However, I don't feel comfortable giving the bike back when it is apparent problems still exist.

Any and all input would be greatly appreciated.

Thanks much,
Brian

Thanks Ken....

Thanks for your quick response.

Actually I have a spreadsheet I created which I use to track the VIN from any Harley I work on which will give the complete rundown of the different VIN characters - this bike is a true XL1200C.

I will be sure to go through your steps this evening with hopes they will fix the issues. Is it worth using a small wire, such as the smallest acetylene torch tip cleaner, to run through those passages as well as using air (as long as the wire will fit without forcing)?


Brian

Hey Ken....

Followed your suggestions to the "T", also reset the idle speed and played with the EZ-Just back and forth, test rides both cold & hot however nothing has changed. Strange thing is the backfire through the carb. I would be cruising right at 45 mph in 5th gear at an easy pace, no acceleration, no deceleration, running a steady throttle and the bike would just pop through the air cleaner. In fact one time it did it 3 times a few seconds apart and then nothing. Also pulling from a stop hasn't changed either; you really need to work the throttle and clutch to keep it from having a major hesitation and falling on its face.

Any other ideas?

Thanks again,
Brian

Thanks Ken...

One of the first things I did was to pull whatever codes may have been present when the bike first came in and there were none. I have also rechecked the codes just to make sure something new hadn't popped up and everything is still clear.

Customer wants to pick up the bike tonight and I have already warned him about the situation. Guess I'll see what he thinks. Problem for me is if it's not 100% up to my standards then it's not good enough.

Brian

Thanks for the input.....

Parts of the job included doing the standard service (bike only has 6900 miles on it) and I went ahead and replaced the spark plugs just as a "because" and went with the Harley double platinum. I also made sure to inspect the wires. Granted, you can't always see wire issues especially if they have an internal breakdown but from my initial inspection they seemed to be "ok" based on the condition of the boots and wire jackets. Most likely I'll grab a set of known good wires as a process of elimination.

The other thing I'm going to do is put the carb back to stock (factory jets & air cleaner) now that it's been cleaned and see what, if any, differences it may make. Will also most likely drain the fuel tank and do a refill since the owner can't tell me how old the gas in the tank is. I have also located a Crank Position Sensor since I know those have been known to cause some erroneous issues.

Nothing but fun and excitement.....

Brian

Oh most definitely.....

I've learned throughout all the years of being in the auto repair industry along with the computer science engineering field that the process of elimination works properly only if each step is done as a stand-alone process.

Yes, I have tested all the known areas for air leaks up to the point of swapping out the manifold to carb seal ring.

Brian

So what are your thoughts with regards to the possible CPS?

As stated earlier, I have checked & double checked the DTCs and all are clear however I have heard of the CPS causing issues without setting codes. Obviously the changing of the gas will happen first followed by the re-fittment of the carb if the gas doesn't work.

...and the Oaky Shade Tree school of wrenches and beer is one of the finest schooling's there is

No matter where the experience is gained, you can't deny what you learn from it and sadly enough, what some people don't learn.

Brian

Ok, so here's the rundown.....

Gas in the tank was very dark. It just looked old especially compared to the new gas. Drained the tank, removed the in-tank filter for inspection / cleaning, drained the carb and put 2 gallons of new gas in the bike. No change - problems still existed.

Back to the shop, removed the carb and put everything back to the way it was when the bike came in (180 main jet, 42 pilot jet, emulsion tube, needle, factory diaphragm spring, etc.) except I left the EZ-Just mixture screw in there because it certainly is convenient. Reinstalled the factory air cleaner even with the backing plate missing.

The bike ran great - no hesitation from a stop, no "coughing" through the air cleaner and I even tried to make it do it by riding the bike at 35 mph in 5th gear. So I have to wonder if the the K&N kit I was using just flows more air then expected and the #46 pilot isn't big enough to flow the required fuel in the low to mid-range scale.

At a loss as to what to do now. I know the customer wants his bike back but I can't say I'm looking forward to eating the cost of both the K&N kit plus the CVP Stage 1 kit - not to mention all the time I have into this. Even as it stands I would still need to get a factory backing plate for the stock setup.

Ken, if you're out there, any chance of getting a couple different larger sized pilot jets just to test my lack of fuel theory or am I more nuts than I'm letting myself believe??

Inputs - suggestions - ideas.....

Thanks to all,
Brian

Hi Ken....

Yeah, I'd have to say I'm a bit confused too. I fully agree about the smaller jet would've caused an even worse hesitation but keep in mind the stock a/c element is back in place therefore reducing the air intake to match the smaller jet. That's why I was thinking possibly a jet larger than the #46 especially if the K&N is flowing some serious air. As of the last test ride last night the bike is completely back to the way it was when it came into the shop except now the carb has been cleaned and installed your CVP basic rebuild kit. I did not take notice of the needle number but will this evening. It just seems really strange that putting the carb back to stock (including the a/c element and missing the backing plate), other than the EZ-Just, the bike was running rather well. I guess that's why I was wondering, and looking for your input, with regards to possibly the K&N kit is flowing more air than what the #46 pilot jet can accommodate.

One thing I was going to try just for fun & excitement was to leave the carb setup as is but see what happens by installing the K&N kit again. Based on my thoughts of the #46 pilot being too small for the K&N, that would mean putting the K&N back in place with the now installed #42 should make the hesitation / popping even worse. If that doesn't happen then I'll be WAY beyond confused . I'm just trying to guess what would've been causing the erratic popping through the carb. I'll tell you, the test ride before I swapped everything back was one of the worst times it was doing the hesitation / popping.

Thoughts?

Thanks,
Brian

Yeah...already crossed that bridge. I wasn't very happy with how K&N had the breather bolt extensions setup by using washers up against the heads so I tried removing those to allow the K&N backing plate to "push" the carb assembly further into the intake seal ring. I even made sure to use some dielectric grease to help with the seal - no difference.

Also, since the stock backing plate is missing there's nothing to bolt on behind the breather bolts which would normally push the carb into the seal ring. With the setup that's on there now the a/c element is bolted onto the carb and it's all one unit with the carb just pushed into the seal ring - nothing to hold it in. I'd love to know what was going through the mind of whoever removed the stock backing plate.

The other thing that's strange about the K&N setup is they have the mounting flange on the back of the aluminum backing plate sitting right up against the carb - no gasket. At first I though the included rubber "velocity stack" acted as the gasket but that's not the case. The aluminum itself makes contact before the rubber does since the rubber is countersunk in the aluminum flange. They do say to use the stock a/c gasket on the FI models. I went ahead and also used it as a test.

Here's a link to the installation .PDF for whatever use it may be.
K&N RK-3929

Brian

So....

This morning I went ahead and took the bike back out with it's stock setup (carb & air cleaner) just to make sure the other day wasn't a fluke - the bike ran just as good as the other day. I then installed the K&N kit and leaving the carb with its stock setup. The bike still ran good with no real detectable differences. I went through the whole process of adjusting the idle air mixture and curb idle. No hesitation, no coughing through the carb even when trying to get it to do it - running at 35 mph in 5th gear. Currently the EZ-Just is set at 3 turns out.

So, right now the carb has it's factory needle, spring, emulsion tube, 180 main and 42 pilot jets. The only non-factory item is the idle air has been replaced with the EZ-Just. As I said in my other post - I'm WAY beyond confused at this point. All the signs pointed to the bike being starved for fuel yet putting the carb back to factory AND adding an additional air source has it running better than the additional air source PLUS the additional fuel from the Stage 1 kit...??

Ken, you had asked about the stock needle number - N4NN

Edit: Just to make sure I wasn't losing my mind I reinstalled the complete Stage 1 kit and the problems came back. My question is which part being incorrect is most likely to be causing the issues - needle, diaphragm spring or pilot jet (or all the above working as a whole)?


Brian

I have an 05 custom and am having the exact same problems. I put carb back to stock and thats the best I can get it to run. I have left the K&N system on and have new slip ons. I would have bet money it would have neede a bigger jet but went to a 45 and rmoved the 42 and that was a mistake so I returned to the 42 and its running better. Only have a little surging at 30 mph. Havent figured this out yet.