Chasing down popping in exhaust

[arse21]

Good morning, you beautiful Valk riding folks.
I have a new Cobra 6in6 exhaust to put on my 97 Valk, but I am currently unable to due to the popcorn machine popping that I have currently within the system. I have perused many threads to try to track down my specific problem to no avail as of yet and I wonder if you fine people would be able to add some guidance? Here's what I've got and what I have done. She has just under 25k miles FYI.

Popping only occurs on the right side exhaust. - mostly burbling pops with occasional POP. However OEM exhaust stifles the sound whereas the Cobra's magnify it

Popping does not occur on idle or decel...only when on throttle (constant or accelerating) or when the choke is on for too long. I hear it most below ~40mph and mostly when on a constant throttle.

Checked the right side plugs. #1 looked okay, #3 burning hot, #5 looked oily. Left bank plugs all looked great, so I swapped them to the right side so the next time I ride I can pull them again and see what changed.

I have desmogged the bike recently which cut down a lot of the LOUD POPs. New vacuum line for #6 to petcock. New vacuum caps for 3 & 4.

This weekend I took the tank back off and double checked airbox connections, intake runner clamps and bolts, exhaust header connections. All tight and secure.

I took off the carb covers and checked the diaphragms for cracks / hard spots.

Drained crankcase breather (which had a ton of crap in it).

I ordered redeye intake orings and additional vacuum plugs for the old vacuum plugs still on the bike. I also just ordered the redeye pilot tool so I may be able to reset the pilot screws to 2.25 turns out if that is what is out of sync, especially since I will be pulling the intake runners anyway. I also have a new air filter on the way FWIW.

I see a bit of debate between how to reset pilot screws, between just 2.25 turns out and or individually resetting with the tach gauge / Honda method. I admit being a novice in the carb world and wonder if I could just turn them out 2.25 and see what happens or if I should really (get some help) and do it with the more intensive method. My additional thought would be to get a carb sync after as well.

To summarize:
Where else could my popping be coming from?
I feel like it may be a rich / lean problem in carb now...can I just turn screws out 2.25 and see?
What else am I missing?

Thanks in advance!

[hubcapsc]

intake orings and additional vacuum plugs for the old vacuum plugs still on the bike.

This 

And the vacuum line to the petcock if you still have OEM...

-Mike

[Tazman11]

Easy check. Exhaust leak. Order some exhaust gaskets, pull the offending side pipes, and inspect and replace gaskets. Many don’t replace the gaskets when they upgrade the exhaust system. Also, make sure there are not old gaskets still in place.

Good luck and best wishes.

[arse21]

tazman - I pulled out old and swapped in new gaskets when I first attempted to put the Cobra's on and have extras to put back in whenever I happen to track this popping down. I don't have the cobras on currently because the popping is obnoxious in them.

hubcapsc  - yes I got some heavy duty 4mm new line for vacuum to petcock. I certainly hope the orings and new vacuum caps fix it!

[Grandpot]

A vacuum leak is one of the causes of popping.  All the hose connections may look good, but still may leak.  Get a spray can of Starting Ether and spray along the vacuum hoses and connections while the engine is at idle.  If there is a leak, the RPM will rise.  Also spray around the O rings on the intake runners and the tubes between the air box and carbs.

[sandy]

hubcapsc  - yes I got some heavy duty 4mm new line for vacuum to petcock. I certainly hope the orings and new vacuum caps fix it!

The original Vac line is 3.5 mm. Could you have a leak there?

[arse21]

hubcapsc  - yes I got some heavy duty 4mm new line for vacuum to petcock. I certainly hope the orings and new vacuum caps fix it!

The original Vac line is 3.5 mm. Could you have a leak there?

Huh, I pulled the 4mm notion off a post from here...I will certainly get some new line and try that!

[..]

I replaced #15 in this diagram and no more popping.

When I took the tube off and bent it I could see many very, very fine cracks and it seems 1,2,3, or more were letting a little air in.

[arse21]

I replaced #15 in this diagram and no more popping.

When I took the tube off and bent it I could see many very, very fine cracks and it seems 1,2,3, or more were letting a little air in.

Which diagram?

[..]

I replaced #15 in this diagram and no more popping.

When I took the tube off and bent it I could see many very, very fine cracks and it seems 1,2,3, or more were letting a little air in.

Which diagram?

I know I posted this link earlier.

Not the first time a mystery has occurred for me.

https://www.ronayers.com/oemparts/a/hon/50541207f870021c54bee648/fuel-tank

[arse21]

I just replaced all intake o-rings and 3 old vacuum caps.

Desmogged everything else, Only a new vacuum line to petcock..

Tightened everything else up and I still have a constant burbling/popping when on throttle, especially low Rev / constant throttle. This is only on the right side of the bike.

I'm on tank 3 with seafoam to see if there's any gunk inside.

I ordered redeye stubby  D tool to potentially adjust carb screws, especially noting cylinder 3 burns hot.

I also have new exhaust gaskets on the way (replaced them once already trying to put the Cobras on, swapped back to OEM).

Sprayed the tops and bottoms of all clamps above and below carbs with started fluid to see if any revs run high, nothing there.

What else could I possibly be missing? I'm hoping carb tweaking on bike will do it...but I'm running out of ideas!

[Savage]

Could be a bad air cut valve.

[Skinhead]

There are hoses on each carb that may crack and cause a leak.  The starting fluid test may identify this issue, but make sure to inspect hoses by looking at them end on, several times the cracks occur radially where the hose is stretched over the fitting.

[arse21]

There are hoses on each carb that may crack and cause a leak.  The starting fluid test may identify this issue, but make sure to inspect hoses by looking at them end on, several times the cracks occur radially where the hose is stretched over the fitting.

Gotcha, thanks I will take a look next chance i can. For sake of it what size hose are they if need be replaced?

[98valk]

I use Honda 07mma-mt3010b pilot screw wrench to adjust the idle mixture screws.

[Skinhead]

There are hoses on each carb that may crack and cause a leak.  The starting fluid test may identify this issue, but make sure to inspect hoses by looking at them end on, several times the cracks occur radially where the hose is stretched over the fitting.

Gotcha, thanks I will take a look next chance i can. For sake of it what size hose are they if need be replaced?

I'm not sure on the size.  Those on the carbs are small, a couple of mm's.

[arse21]

I use Honda 07mma-mt3010b pilot screw wrench to adjust the idle mixture screws.

I have Redeye stubby tool somewhere in shipping land to do this as well. Cylinder 3 runs hot, white electrode on spark plug and significant bluing on exhaust from that cyl in comparison to every other pipe.

[98valk]

I use Honda 07mma-mt3010b pilot screw wrench to adjust the idle mixture screws.

I have Redeye stubby tool somewhere in shipping land to do this as well. Cylinder 3 runs hot, white electrode on spark plug and significant bluing on exhaust from that cyl in comparison to every other pipe.

not easy to read plugs due to unleaded gas. white electrode isn't an indicator of being lean.

https://www.enginelabs.com/engine-tech/reading-the-plugs-spark-plug-tuning-with-different-fuels/

[eRaGoN]

had same issue with the i/s....check cylinders 1 3 5 if  any of the cylinders are not working  by pulling the each plug wire and notice if the rpm drops down

[98valk]

more on plug reading. my last dyno run was pig rich on the top end and the porcelain was bone white and still made close to 120HP on a FactoryPro dyno which really is a Mustang Dyno.

https://www.dragstuff.com/techarticles/how-to-read-plugs.html

 good info

https://www.strappe.com/plugs.html

[arse21]

had same issue with the i/s....check cylinders 1 3 5 if  any of the cylinders are not working  by pulling the each plug wire and notice if the rpm drops down

Well, interesting! I pulled 1 3 5 plug wires. 1 had no drop, 3 definitely dropped, and maybe a little drop in RPM. Where the bike idles, decals, and fast accelerates without popping, might this be a slow jet issue? Started doing some reading here on that last night...maybe in panic of that being the issue.

I popped a half can of techron in there this morning, riding, sitting, riding, sitting...but it still feels like I'll have to find. Way to get the slows out. Does this seem like my likely next step?

Also, 98valk, I read. Ton on your often linked info on TWC3 2stroke oil in gas and picked some up to run in the bike...also feel like it won't be enough to clear those slows, if that is what this is

[98valk]

had same issue with the i/s....check cylinders 1 3 5 if  any of the cylinders are not working  by pulling the each plug wire and notice if the rpm drops down

Well, interesting! I pulled 1 3 5 plug wires. 1 had no drop, 3 definitely dropped, and maybe a little drop in RPM.

first I suggest u make sure u have a good spark on all the plugs.
have u checked the resistors in the plug wire end cap? very rare but there has been a report of a failure.  have u checked the plug wire going into the coils? they are held in there via a plastic compression fitting setup whereas the wire end is pushed onto the metal spike from the coil.  wire could have been pulled loose, and/or corrosion, etc. plug wires are copper metal core wires.

also measure the ohms of the plugs. I take reading of all new plugs I install and check them every oil change.
I had a plug fail on my DR200. had to keep rpms at 5-7k just to keep it running, was only a few miles from home so made it back. I measure the plug after checking the other usual suspects, and found it way out of range. interesting was I had only owned the bike for a few months and only had it a little over 1k miles on that new plug. so u never know.

[arse21]

had same issue with the i/s....check cylinders 1 3 5 if  any of the cylinders are not working  by pulling the each plug wire and notice if the rpm drops down

Well, interesting! I pulled 1 3 5 plug wires. 1 had no drop, 3 definitely dropped, and maybe a little drop in RPM.

first I suggest u make sure u have a good spark on all the plugs.
have u checked the resistors in the plug wire end cap? very rare but there has been a report of a failure.  have u checked the plug wire going into the coils? they are held in there via a plastic compression fitting setup whereas the wire end is pushed onto the metal spike from the coil.  wire could have been pulled loose, and/or corrosion, etc. plug wires are copper metal core wires.

also measure the ohms of the plugs. I take reading of all new plugs I install and check them every oil change.
I had a plug fail on my DR200. had to keep rpms at 5-7k just to keep it running, was only a few miles from home so made it back. I measure the plug after checking the other usual suspects, and found it way out of range. interesting was I had only owned the bike for a few months and only had it a little over 1k miles on that new plug. so u never know.

And this is why I post on this forum! Thanks, I will take a look at plug wires tomorrow when I get a chance. Getting colder up here in Maine, wanna keep riding til they salt the roads...and it might be nice to do it with those expensive Cobras that are sitting on a shelf collecting dust currently.

[arse21]

Rode to my shop. First off, took an IR heat range of pipes. Pipes for cylinder 1 and 5 significantly colder than 3, 2, 4, 6.

Pulled the right side bank plugs out, inserted them back in the wire, grounded them, and started the bike. All 3 showed spark on the right side.

Pulled the coil end off of 1 & 5, they both looked fine, no corrosion, connections were tight to begin with. Also took off #6 for comparison of running a multimeter on bad cyls (1&5) and apparently fine cyl 6. All 3 spark plug wires had similar ohm registry (which of course I have forgotten what numbers were pulled.)

Set up a timing light gun and connected to each wire 1 3 5 and that light flashed for each plug wire.

I got my Redeye pilot adjustment tool and checked right side pilots. 1.5 turns out on each of them. I moved them out 1 7/8s for now.

Still have popping when on constant / slow accelerating throttle...not on decel or WOT. 

I am going to pick up a compression gauge and a peak voltage meter to check those off of my list as well...just didn't have them in the shop tonight. My thoughts at present (might be wrong) but I can't but to think, seeing spark and seeing the voltage trigger the timing light, that the wires are good and the coils (not failing on both plugs 1&2, 5&6...only 1....only5) are good, so other electrical should be fine? Next up will be compression...and if that isn't it I feel I will have to dive into carb clean.

Also, over the past tweaks, it seems that when the bike warms up my idle moves from 900/1000 to 1500 plus while riding. I do seek a carb sync at some point...and also feel that I have other work to check off on the bike before I sync.

Please send help. The bike doesn't even have 25k miles yet for a 25 year old bike.

[98valk]

4. Idle and low rpm cruise

        Fuel Screw setting (AKA "mixture screws")
            There is usually a machined brass or aluminum cap over the fuel screws on all but newer Honda. It's about the diameter of a pencil.  Cap removal details. Newer Honda carbs have no caps, but use a special "D" shaped driver, usually supplied in the carb recal kit. We do have them available separately, too. 800 869-0497 to order -
        Set for smoothest idle and 2nd gear, 2000 rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear, 2000 rpm steady state cruise , and 1/8 throttle high rpm operation.  (pj tuning information)
        Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel level in Step 3 - which you have already done!) AND pilot jet size are the primary sources of mixture delivery during 2000 rpm steady state cruise operation.
            If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
            Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
                NOTE: A rich problem gets worse as the engine heats up.
                    If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
                NOTE: A lean problem gets better as the engine heats up.
                    If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!
http://www.factorypro.com/tech/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

[98valk]

the idle mixture screw needs to be btw 2 to 2.5 turns open for a valkyrie.

(Using another "rule of thumb", if you have the correct pilot jet, the fuel screw will end up at between 1.5x and 3.0x when set for best idle.)

Pilot Jets

The affect of pj size change on idle and cruise operation

http://factorypro.com/    click on product support, then motorcycle tuning tech, scroll down to "Pilot jet, effect of size on idle and cruise"   to read full article.

[arse21]

the idle mixture screw needs to be btw 2 to 2.5 turns open for a valkyrie.

(Using another "rule of thumb", if you have the correct pilot jet, the fuel screw will end up at between 1.5x and 3.0x when set for best idle.)

Pilot Jets

The affect of pj size change on idle and cruise operation

http://factorypro.com/    click on product support, then motorcycle tuning tech, scroll down to "Pilot jet, effect of size on idle and cruise"   to read full article.

I appreciate the homework assignment...will read when I get a chance to.

Pardon my ignorance to this, but where the left bank has not demonstrated ANY difficulties, when adjusting PJ screws, should I be adjusting ALL of them out or focus on the right bank screws?

When I happen to get the screws (hopefully) to a point of reducing the popping, I do intend on getting a carb sync done as well.

[Hook#3287]

I don't see in your posts where you have confirmed the "Air cleaner connecting tubes" are installed correctly.

Not sure if that would cause your symptoms, but it's good to check anyways.

[arse21]

I don't see in your posts where you have confirmed the "Air cleaner connecting tubes" are installed correctly.

Not sure if that would cause your symptoms, but it's good to check anyways.

Yes that was the first thing I double checked going back in. Dental Mirror and reclamping down on the top of the carb! Absolutely worth the mention.

I took a half turn out for each of the right side bank this morning and may have diminished some of the popping...Will take another look when able to get out for a ride longer than just going to work.