The dreaded carb cough and interesting findings

[wrkdWS6]

Good luck, I’m thinking it’s the manifold seals also. If you happen to hear popping from the exhaust under decel I’ll almost guarantee the manifold is the culprit for all this. Sometimes dumb stuff like that can be a real PITA.

When you reinstall the manifold, you can lightly put some silicone lubricant on the seals if you wish, may aid with making a nice seal to the cylinder heads. I use Sil-glyde, I’m sure Vaseline would be fine too. The bolts can be a PITA to get to, to make the reinstall and any future manifold removals and reinstalls easier, you could consider replacing the 2 primary side bolts with standard 5/16-18 x 3/4 hex bolts.

[gearbanger]

Originally Posted by wrkdWS6

consider replacing the 2 primary side bolts with standard 5/16-18 x 3/4 hex bolts.

Thank you for providing the correct sizes! I went ahead and purchased x4 of them to make reinstall easier, and final tightening possible (I hope) with the carb and backing plates fully mounted. Just waiting on some super lube to execute the seal replacement.

I can't tell looking at your photo, but did you use washers for the standard hex bolts? I know the original screws do not utilize washers but figured I'd ask to see if you did.

[wrkdWS6]

Nope, no washers, you’re good!

[gearbanger]

Alrighty! That was relatively painless. Swapped out the intake manifold seals and the manifold to carb boot as well. I used a liberal amount of super lube and even went the extra mile by polishing up the intake manifold faces where the gasket sits with flitz. I replaced the manifold mounting bolts with four hex heads which made for a very easy reinstall. I couldn't tighten down the carb side bolts with the carb on like I had hoped (If I had an articulating 1/2 crescent wrench maybe...) so I got the center alignment as best I could with the carb on and the angle of the manifold matched to the breather threads on the head as close as I could with a gauged protractor. When tightening down I was sure to do a half turn on each side respectively as to not warp the flanges. I also checked the needle jet again and it is in fact installed correctly and I dropped the pilot down to a 45 with 2 turns out on my IMS. New NGK DCPR7E gapped at 0.040 and she starts up! Finished the job a little late to take her for a spin but will update everyone after a good warmup, idle and IMS adjustment, and a long test ride.

Fingers crossed... or else its back to the drawing board

[gearbanger]

I have an update after replacing the intake manifolds... I still have the carb cough. No change in symptoms and is acting the same before the manifold seal replacement. I want to get a few miles on the new spark plugs before pulling them to see if there is still a lean condition within the front cylinder and will most likely be checking that in the middle of the week.

What else is there to check? I was thinking of changing my exhaust gaskets next... could that be a source to the problem? Is this a sticking valve issue? Timing chain for cams?

In addition, I did an IMS adjustment again as per sportsterpedia's instructions.

http://sportsterpedia.com/doku.php/t...ting_air_leaks

45 pilot jet installed

I set the idle adjustment screw to as low of a smooth idle as possible (probably around 600 rpm) and could not get the bike to fall off idle while unscrewing (enrichening) IMS. I could get the bike to fall off at 3/4 - 1 turn out from slightly seated (leaning) the IMS.

I figured I'd leave the IMS at 2 1/2 turns and set the idle speed screw to about 900 rpm (by ear) and seems to be running good with less carb coughs. I did get one or two, but I might just have to live with it and stop trying to perfect it... Or until someone on here has another idea that I haven't tried!

[IXL2Relax]

Sounds like it's getting better. I'm glad you're moving in the right direction.

Do consider that sometimes, it is near impossible to eliminate every condition where a carb fart may occur, without extreme patience & dogged fiddling efforts to correct that very specific condition. While it is very common for owners to simply add enough fuel overall to prevent any lean spots in the carb operation, that is not really a proper solution, either.

How do the plugs look? Even burn to each other? Proper color, not rich or lean?

Once you set the IMS screw (to 2-1/2 turns out, which was a guess) were you able to further close the Throttle Plate? If the Transfer Ports are flowing fuel at idle, that will affect the IDM & IMS setting. Tranfer Ports flowing during idle might also mask an air leak.

Make sure you have no air leaks by using an unlight propane torch flowed all around the intake seals. Your IDM results (not getting a rich drop off point) might indicate you still have a lean condition. This makes me want to super verify against air leaks.


================================================== ============

I'll cover a couple issues that may or may not be at play.

Seals Air Leaks - In the past spraying brake fluid (or other combustible sprays) around the intakes to verify where their ingestion would show a leak. However, most of the previous combustible cleaners have now been reformulated to reduce or eliminate combustion. This is the reason that Unlit Propage is considered the appropriate substance to check for air leaks.

Vacuum Air Leaks - On bikes with either a VOES or vacuum-operated petcock, the vacuum hose sometimes becomes brittle and cracks causing additional intake air. When these items are removed, the method of sealing the vacuum port on the carb becomes a factor for future air leaks.

Idle Drop Method of tuning - Idle Jet, Transfer Ports & Idle Port
A complex consideration for perfect tuning.

Be sure to read this Sportsterpedia section regarding the relationship of these parts:
http://sportsterpedia.com/doku.php/t..._balancing_act

You should also check your Ignition Control Module part number (software level).
From the Sportsterpedia: (http://sportsterpedia.com/doku.php/t...ection20042006)
The Ignition Control Module for these years is programmable by the dealer to match the specific model bike, either 883 or 1200. It is mounted under the seat. The part number on the ignition module is really the version of the internal software that was last flashed into the module. The module may have started out as a 32478-04 (or 32622-04) module, but it might then have been upgraded to 32622-04A. Later built models would have had the latest upgraded part (software) installed from the factory. As of 2020, the 32622-04C is listed as correct for all 2004-2006 models (then programmed for 883 or 1200) and older modules are recommended to be upgraded to that level.


IXL _______ >>>> My Motorcycle Chronicles Are Here <<<<
For Sportster Tech Info:
Ride On The Sportsterpedia - A Toll-Free XLForum Information Highway!

[gearbanger]

Originally Posted by IXL2Relax

How do the plugs look? Even burn to each other? Proper color, not rich or lean?

Here are the new plugs I put in (NGKDCPR7E) gapped at 0.040 each with only 50ish miles on them after the manifold gasket replacement.





The darker of the two plugs is the rear cylinder, same as before I changed gaskets. The darker plug is dry, its carbon. Not oil.

I ordered some rubber lip James Gaskets and new intake manifold flanges as well and will change them again when the parts arrive. Its possible that maybe the flange is warped and not sealing well.

https://www.jamesgaskets.com/product...07887fb0&_ss=r

I might try to adjust the IMS again and get the idle right but I don't think it will make a difference given the discrepancy in color of the spark plugs.

Another detail I might add:
With the current 45 pilot and 2 1/2 turns out on the IMS screw, I've set the idle to as close to 900-1000rpm with my ear, after riding under load and coming to a stop or a red light, the idle wants to hang before dropping down. It will settle if I let it, or will drop down after engaging the clutch slightly.

I have a feeling the seal is still not good, hence ordering the new gaskets. The ones I used for the job were the standard HD intake manifold gaskets and these new rubber lip ones sure do have more material to them. Should I be considering exhaust gasket leaks too? Possibly an issue with a valve?

[Tomcatt]

Try it with the IMS 3 1/2 turns out. See how it runs and if your idle speed changes.

[wrkdWS6]

Hanging idle indicates to me either: too lean of a idle mixture setting or leak in the intake tract somewhere. I’d start with what Tom suggested.

Those exhaust to head nuts should be about 120 in lbs. if you want to check them. I don’t think they are your issue but good to check as they do come loose sometimes.

In my experience riding and owning CV carb bikes, that damn carb will on occasion fart even when properly tuned. After running S&S and Mikuni carbs I would never again use a CV. Once you get it to where it only farts or coughs when cold or once in a blue moon when blipping the throttle when warm, that’s about as good as it’s gonna be IMO.

Once idle is sorted, could play with the needle height (maybe one notch change) to see if that helps in a throttle blip situation, so long it doesn’t muddle the mid-range of course.

[Tomcatt]

At this point it might be worth running compression test to make sure you're not trying to tune out a mechanical issue.

The other thing I wonder about is your throttle blade position. If your throttle blade is out of position (open too far) relative to the transfer ports you're just chasing your tail trying to get your off idle tuning sorted out. The only way to be sure is pull the carb and look into its' bore from the manifold end to see where the blade sits relative to the transfer ports.

I'd still try the IMS at 3 1/2 turns first. It's easiest and will tell you something.