popping and backfire

[NDFRC]

I think I have read thru pretty much every thread on this and I get most of the high points.
03 STD; changed out exhaust to glass packs, de-smoged(CA), replaced intake orings, replaced oem w/pingle shut off, added fuel filter, new oem air filter (carbs were all cleaned and synced 1000 miles ago). Now I have a loud bark/pop at cruise, say 2-5k rpm. Have checked and rechecked every vacuum plug/hose, intake boots/clamps, header bolts.
Everything seems in order, starts right up, sounds good, accelarates strong- no pops, can deccelarate long and hard- no pops, its just at cruise and just on the right side, i can somewhat control it, by easing up or pushing a little, but to be right at criuse its loud and embarrasing. Tonite I will check the plugs to see if they tell a story-replace if needed(replaced them about 500 miles ago), just trying to find out what area is most likely the problem. I dont think its a vacuum problem, but now I am not only miffed, but so dissapointed shes not feeling well. Will carbs out of sync cause this symptom? hate to have the local dealer charge 2 hour labor rate if it wont help(and am afraid they might make things worse), is there anything else simple i need to be checking?

[Chrisj CMA]

use a mirror on an extension, you know those little ones  and a flashlight to see the backs of all the plastic tubes going from the airbox to the carbs.  tighten all the intake clamp screws (18 of them) and if that's not itI would think about removing and very carefully re-installing the right side exhaust.  It is possible to get a header cocked so there is a leak.  Did you use new gaskets when you changed the exhaust?  If no.....get a new set and at least do the side that's popping.

[NDFRC]

I was dilligent in making sure all the air tube connections were good, from air box all the way down including the clamps at the bottom of the carbs and top of the intake runners. I did replace exhaust gaskets, made sure the old copper ones came out and replaced with the green crush ones, i have been checking for tightess after each ride, thinking this is the issue, i dont hear any leaks and i thought exhaust leak backfiring happens predominately on decel.. which i cant make it backfire no matter how hard i decel.

[O-B-1]

Make sure your plug gaps have not widened beyond specs.

Too wide a gap can cause spark "blowout" due to gas velocities, especially at mid to high RPM ranges

[Patrick]

What Chrisj said. Plus check all the vacuum caps, they're famous for going bad quickly.

[Ricky-D]

I would tend to think that any backfire while cruising at a steady throttle (on) position, and identifiable as coming from the same source, (the right side) is not going to be fuel related.

I would first change spark plugs and then the spark plug wires, suspecting them to be the source of the problem backfiring.

This is in view of your report that the carburetors have been synchronized. Which really has little affect regarding your problem since synchronization mainly is an "off throttle" adjustment.

***

[signart]

In addition to already good suggestions, and since you have eliminated many of the possibilities, carefully examine the rubber vacuum piston under the round carb covers. Especially if you had them off for carb service. I have to remove mine to service carb bank because of velocity stacks and one got out of position on assembly and acquired a tiny tear, which caused a bad flat spot and pop until it passed a certain rpm. At WOT it ran normal. Good luck and hang in, you'll get it.

[nogrey]

Reviewing the Valkyrie shop manual, your symptoms suggest the following possibilities:
Symptom: Poor performance at high speed:
1) (Fuel supply is suggested, but where it is only one cylinder I think this is unlikely, though not impossible. Many have had issues with fuel filters and since there is one already in the tank, the redundancy is really unnecessary and problematic)
2) Carburetor clogging. (This seems a possibility as only one is at issue)
3) Valve timing - check timing belts and tensioners.
4) Ignition timing - Faulty ICM or Pulse generator
5) Check valve spring - weak or broken.

I would pull the top cap off the offending carb banks and check the diaphragm for cracks. A cracked diaphragm will cause problems of this nature.

[Bigwolf]

You have done quite a few things.  IE:

changed out exhaust to glass packs, de-smoged(CA), replaced intake orings, replaced oem w/pingle shut off, added fuel filter, new oem air filter (carbs were all cleaned and synced 1000 miles ago)

  Did the bark/popping start right after that work? 

With the described symptoms, the first thing in my mind is the intake tubes (you already checked them) and the intake O-rings.  Are you sure that an intake O-ring did not slip when you installed it?  Next, I would check out the diaphragm/vacuum piston as signart suggested.    If the problem is not there, then I would run a compression test to verify mechanical integrity.  I would, of course, check the plugs as I pulled them to identify any problems or indicators there.  Normally an ignition problem would affect both sides of the engine but a badly gapped plug could affect only that one cyl.

[R J]

You have done quite a few things.  IE:

changed out exhaust to glass packs, de-smoged(CA), replaced intake orings, replaced oem w/pingle shut off, added fuel filter, new oem air filter (carbs were all cleaned and synced 1000 miles ago)

  Did the bark/popping start right after that work? 

With the described symptoms, the first thing in my mind is the intake tubes (you already checked them) and the intake O-rings.  Are you sure that an intake O-ring did not slip when you installed it?  Next, I would check out the diaphragm/vacuum piston as signart suggested.    If the problem is not there, then I would run a compression test to verify mechanical integrity.  I would, of course, check the plugs as I pulled them to identify any problems or indicators there.  Normally an ignition problem would affect both sides of the engine but a badly gapped plug could affect only that one cyl.

A faulty plug wire can do the samething.

[NDFRC]

wow thanks.. a lot of good info, did not know about the diaphragms in the carbs, I will check those(a Honda shop did the earlier carb sync). As far as the intake orings, yes i was careful, infact all the reading i have done on how easy it is to 'not-get-it-right' and the resulting issues, i am overly cautious with any effort that i do, ask my wife, she call me Sheldon. When i pulled the plugs, they looked lean, not overly white but not a nice tan, I am guessing thats from changing the exhaust, as the plugs were nice and brown/tan when i changed them the first time(1000 miles ago and b4 the exhaust change), number 5 was black, i changed it, all were gapped right (34), aside from the popping I think i am seeing another problem(and it feels worse) 2 nights ago it started loading up at idle and blows blue smoke from the right side, it clears when you run it, but starts again when sitting at idle or overnite, it runs strong but blue smoke cant be good, when i found the black #5 plug i hoped the smoke was just from a fouled plug, but it continues after I put in a new one. I dont know if the backfire and now the smoking are related. I think I am going to try valve adjustments and hope its simple as that. The bike has 3500 miles on it, I have put on 1000. I did the exhaust mod first, no popping, there was a slight decel backfire, which caused me to do the de-smog, the decel backfire stopped but the popping at cruise started- at that time I also replaced the petcock and air filter, since then I changed the intake orings to try and stop the pop, no change.

[nogrey]

wow thanks.. a lot of good info, did not know about the diaphragms in the carbs, I will check those(a Honda shop did the earlier carb sync). As far as the intake orings, yes i was careful, infact all the reading i have done on how easy it is to 'not-get-it-right' and the resulting issues, i am overly cautious with any effort that i do, ask my wife, she call me Sheldon. When i pulled the plugs, they looked lean, not overly white but not a nice tan, I am guessing thats from changing the exhaust, as the plugs were nice and brown/tan when i changed them the first time(1000 miles ago and b4 the exhaust change), number 5 was black, i changed it, all were gapped right (34), aside from the popping I think i am seeing another problem(and it feels worse) 2 nights ago it started loading up at idle and blows blue smoke from the right side, it clears when you run it, but starts again when sitting at idle or overnite, it runs strong but blue smoke cant be good, when i found the black #5 plug i hoped the smoke was just from a fouled plug, but it continues after I put in a new one. I dont know if the backfire and now the smoking are related. I think I am going to try valve adjustments and hope its simple as that. The bike has 3500 miles on it, I have put on 1000. I did the exhaust mod first, no popping, there was a slight decel backfire, which caused me to do the de-smog, the decel backfire stopped but the popping at cruise started- at that time I also replaced the petcock and air filter, since then I changed the intake orings to try and stop the pop, no change.

OK, now you've really got me thinking perhaps there's too much oil in it. Check it before running it any more. Not trying to be insulting, but remember to check it with the bike standing upright. You can use a jack, or just by sitting on it. I sold a Valk to a guy a couple of years ago. It only had 16K on it. I ran into him last year and his bike was blowing blue smoke on startup. He told me he had accidentally overfilled it and was on his way to correct the issue. Personally, I wouldn't ride it another inch knowing that. Anyways, might be just fine, but I would sure check it.

[NDFRC]

Good call, I did check the oil.. religious about that.  thanks.

[Bigwolf]

A faulty plug wire can do the samething.

Nice catch RJ.  Ricky had covered that earlier too.

3500 miles

  Why such low mileage?  Did this bike ever have hydrolock?  If it has had hydrolock, you could have a blocked oil return in the bottom of the rear case.  If it has not experienced hydrolock, I would be suspecting a low compression reading on #5 and I would not start it until I knew why.

Bigwolf

[NDFRC]

ok.. got the #5 plug wire replaced, with a new plug, rode it and no smoke, seemed to run better, the at cruise only backfire/popping seemed to be less but still there, next i am going to swap out the exhaust gaskets on the right side, going to use copper instead of the 'not automotive' crush ones I used the last time. Is adjusting carb rich/lean hard to do?

[nogrey]

ok.. got the #5 plug wire replaced, with a new plug, rode it and no smoke, seemed to run better, the at cruise only backfire/popping seemed to be less but still there, next i am going to swap out the exhaust gaskets on the right side, going to use copper instead of the 'not automotive' crush ones I used the last time. Is adjusting carb rich/lean hard to do?

So far as I know, the only way to adjust fuel mixture at rpm over 3K is with new jets. Low speed has a pilot screw adjustment but that is not in question here. I'm liking your idea of attacking the crush washers again. Two other thoughts come to mind here:
1) You say you desmogged. I just repaired a very interesting problem on a '98. In short, they had desmogged it years ago without issues. Suddenly, a problem developed that sounded like a leaky exhaust gasket. We replaced them twice. Had it narrowed down to cylinder #4. To make a long story short, they had used JB Weld to plug the intake of the crankcase breather tubes instead of rubber plugs. Because JB Weld is only rated at max temp of 550 degrees, the two tubes they had plugged on the bottom of the heads (nearest the exhaust) had failed because the JB Weld had essentially turned to powder.
2) Air Cutoff Valves: During a desmog, the air cutoff valves (little plastic valves on the side of each carb) are not touched. Yet, they have aging vacuum lines on them that can leak and cause issues. Take a look at the hoses on them. Best way to do it is to just get a new set and plan on replacing them. A bad hose on an air cutoff valve can cause a miss on a single cylinder.

Keep plugging away at it. You'll get there.

[NDFRC]

thanks for clearing up the pilot jet thing, that helps (I just bought Red eyes pilot tool  LOL) and i like the idea of not having to mess with those. I did the desmog using Red Eyes shiny kit so am comfortable with all plugs(4 on the top and 2 on the bottom). I did replace those small lines you mention on the sides of the carbs, as for vacuum lines, i removed all that i could and replaced what stayed(i didnt touch the drain tubes, those are not vacuum related right?)
I really do appreciate all the feedback and say again Thanks to everyone! it really helps. 
I am crossing my fingers on the exhaust gasket replacement, but i dont know, i have checked and i dont see or hear any leaking and would think that an exhaust leak would be prevalant on hard decelaration, i have non of that, she runs out strong, idles nice but man right at a steady cruise 2-3k rpm, she just pops and barks out of the right side, and yes this started after the desmog, right now if someone asked me if i would do a desmog, i would say, if its not broke, then hell no leave it alone!!

[cma1]

the Honda engineers spent long hours for many weeks without sleep or Budweiser, trying to figure out a way to make the right bank of the Valkyrie "POP" on deceleration.

they did this because they thought it sounded cool. there is no cure for it, it's built in to the motor. I have tried every cure ever talked about on either forum, every Honda mechanic I could find, and tore down, changed, tightened, re set, balanced, and stood on my head.

nothing works long term. so I decided they were right ! it sounds kinda cool. once I made that decision I stopped stressing about it, besides it scares the crap out of those guys on the corner with the work for food signs.

[Ricky-D]

No popping or similar occurrence when you are

running the stock exhaust system, un-modified.

Mess with the exhaust and you will most likely

get, what is complained about adnauseam.

***

[NDFRC]

ok replaced the exhaust gaskets and it wasnt the problem, the old looked like they had a real good seal. Now am just about convinced whatever the issue is, its with the #5 cyl, it has to be the one backfiring- the plug in that one burns black, i can feel it miss, when you first start it the #5 header is about half a hot as the other 2. It feels some what better to isolate 1 cyl instead of the whole side.
So i guess i need to go thru everything relative to #5. I get what the last comments are saying, but this is not a cool backfire on decel and any mods wouldnt just affect 1 cyl, it would be across the board.
Q; if a coil goes bad, could it affect just 1 cyl and not the other, or would it be both?

[Ricky-D]

It would affect both cylinders, and you are across the board

incorrect regarding your assumptions.

Do a compression test on the engine, if you think you can identify the

offending cylinder. This will verify whether you are correct, or not.

Run some gas additive.

A carburetor synchronization would be suggested.

***

[eight_pockets]

I've been looking for answer to a similar concern.  On decel (with the bike in gear, no gas, coasting) I get popping from both sides.  Since the bike is in motion, I can't tell what cylinder it's coming from, but they all sound fine at idle.

No mods (to my knowledge).  I've had the bike since October, and it's pretty consistent.

[nogrey]

This all happened after your desmog and pipes, as well as intake o rings. I think I'd check the O rings for a leak. Use gasket material. No reason the pipes should cause this, especially on a single cylinder. If this had just happened, say, during a ride one day with no mods, I would suspect a plug wire or an ICM, but if it is this, it's just a coincidence. It sure sounds like an air leak or vacuum. Not sure what else to tell you.

[NDFRC]

it started after i did pipes and desmog, i replaced the intake o-rings after, trying to fix the problem.
 i will though, check that oring to be sure. last night i checked the spark on #5 it was yellow and weak, i will replace the coil. Compression test looked good across all 3, i think i can rule out valve train. I want to take the tank AND airbox of again and redo that, to again make sure of vacuum leaks, but i will wait to see what the new coil does. if that doesent fix it then carb is next and i am not comfortable jacking with carbs,
in fact the more i do this the more i think i want a fuel injected motor, perhaps a new ride is in order.
 

[OzarkRider]

I had a similar problem. I replaced the o-rings but the problem persisted. So while the bike was running I sprayed carb cleaner around the where the chrome carb tubes meet the heads, the motor idled differently, air was getting in past the o-ring on one cylinder, I removed the tube and found a hairline crack in the tube base. Replaced the tube and all is well.

 

[nogrey]

it started after i did pipes and desmog, i replaced the intake o-rings after, trying to fix the problem.
 i will though, check that oring to be sure. last night i checked the spark on #5 it was yellow and weak, i will replace the coil, I am not convinced you can rule out a coil if only one cyl is miss-firing(as many have said on here), even though each coil supports 2 cyls, each coil has 4 leads- 2 ground and 2 primaries- one for each cyl, if the coil only had 1 ground then i would buy it, but with each side of the coil having a ground and primariy for each cyl, i think there are 2 internal coils in one. Compression test looked good across all 3, i think i can rule out valve train. I want to take the tank AND airbox of again and redo that, to again make sure of vacuum leaks, but i will wait to see what the new coil does. if that doesent fix it then carb is next and i am not comfortable jacking with carbs,
in fact the more i do this the more i think i want a fuel injected motor, perhaps a new ride is in order.
 

Sorry you're having so much trouble with your Valk, but you really will have a great, low-maintenance ride once you get past this bug. I hear you on the fuel-injected engine piece, I think the same thing at times, but love the valkyrie so much that I just grin and bear it.
One thought on the coil idea: I had just gone through a valk that was running well but needed some serious cleaning and painting on the engine block. No physical changes were made but had it disassembled down to the top of the engine (tank, air box, carb bank off). Put it all back together and it ran like crap. I found that I had inadvertently put a black screw on one of the ICM coil modules where the ground wire connects to the frame. Apparently the black coated screws have a high enough impedance to cause poor connection and thus weak firing. Since you're pulling the tank off, check the ground screws (the one I had "wrong" was on the left side of the bike mounted to the frame just above cylinder 4). I'd sure like to see you get this thing running. Keep at it!

[NDFRC]

thanks for the insight, i will do those checks, as for my bike, she is the most beautiful bike i have ever seen, the engine is the most asthecially pleasing symphony of machinary on any bike(in my opinion), even if i get new, not to worry.. am keeping this one. period.

[cma1]

one of the guys here in town has converted his valk to fuel injection, I rode with a group of bikes over into Utah with him a couple months ago, he didn't stop for gas till salina Utah, 198 mi. I gotta find him again and see what the heck he did. he didn't even have an interstate tank, he did it on his stock 5 gal tank.

39.6 mpg ?????????????????????

[nogrey]

one of the guys here in town has converted his valk to fuel injection, I rode with a group of bikes over into Utah with him a couple months ago, he didn't stop for gas till salina Utah, 198 mi. I gotta find him again and see what the heck he did. he didn't even have an interstate tank, he did it on his stock 5 gal tank.

39.6 mpg ?????????????????????

That's pretty cool. Got my curiosity up. I wonder if he just retrofitted the same model year gold wing motor?

[cma1]

don't know, I know one of the 1500 wings had fuel injection that would work on the valk. but I think they are pretty much collectors items, I would bet he retrofit a system off a newer gold wing. if I see him around i'll find out, I'd do it in a heartbeat.

[NDFRC]

okay..  pulled tank checked all connections, . again.. replace 5/6 coil, runs better- still pops, but after replacing a bunch of parts, good news is i know what the problem is.. wish i would of tried this a while ago.. its running to lean..  when going down the road popping and cracking, i gave it a little choke, about 1/4 and it stops, take off the choke and it starts again. I could of done that a couple hundred bucks ago in new parts, but heck so it goes. so i guess she needs a re-jet? will it hurt to run with the choke partially on until that's done?

[Farther]

It might be just a mixture screw needs adjustment but it sure sounds like a vacuum leak.

[cma1]

lets ask the inevitable question.

how many folks who have NEVER modified their exhaust system are having the popping problem?

[Visseroth]

Have you ohm'd out the coil on #5 by chance? My bike just recently started running like crap too. Crackling while holding the throttle steady and just sounding deep and not right while cruising flat ground. Gets worse as the bike gets warmer. I ohm'd my coils and found 2 to be pretty crappy. I still have yet to replace them but noticed your post and thought I'd throw it out there.

You should get about 3 ohm's across the positive and negative terminals and 10M ohm's through the spark plug wire, through the coil to where the coil mounts to the bike. At least that's what I understand from what I've read.
It's worth taking a look.