Exhaust popping

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redglbx
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Exhaust popping

#1

Post by redglbx »

So, I’ve been having for some time now popping at idle in the exhaust that seems to come & go. I’ve done a number of things to fix this but it seems to still happen. Major back surgery and a torn meniscus in my knee has limited my ability to chase this. Other than the popping at idle the bike runs very well.

So I’m going to have the knee fixed this week and wanted to see if I could narrow things down on the problem so yesterday I started it from its winter sleep and brought it up to temp and it was popping out the exhaust pretty good. I was figuring I had a bad or burned exhaust valve so I did a compression test and a leakdown test which should show any problems. The following is those results with 9o-psi supply pressure:

Cyl #. Compression PSI. Leakdown %

1. 165psi. 7%

2. 165psi. 7%

3. 155psi. 12% ( may be less as testing this cylinder was problematic)

4. 160psi. 6%


So there was no air leaking anywhere which surprised me a bit but all was very quiet. The results tell me that my engine is sound with no valve or ring issues.

One of the things that I was a bit surprised by was the compression because years ago when I milled the heads by .040in and advanced the cam timing advanced to +4deg the cranking compression was at 195-205psi, the things that I see different was then it was taken with no carbs or manifolds mounted just open ports in the heads, while yesterday it was taken with the engine warmed up but complete with carbs/manifolds & aircleaner with the throttle locked open. Also my compression tester is now around 50yrs old so I’m really not concerned, things are pretty consistent and close to the Honda stated ideal 171psi cranking compression. I’m not concerned.

I relearned that I’m not a big fan of leakdown testing because it’s truly a PIA , #3 was the last one I did and I struggled a bit with setting it up and the results varied between 7% and the above 12%, either way I’m not really to concerned. It was a new portable “Chinese” tester as I really didn’t want to move the bike up to my shop to put it on my old Sun machine to do this, I’m not concerned.

So during all this I found that one of the copper spark plug indexing washers I used had extruded out from the plug, it had split and extruded up around the plug. Keep this in mind

So all this tells me that the exhaust popping has to be caused by either a carb issue (highly modified 1100 carbs) or a problem with the Dyna ignition or coils, kinda leaning towards the Dyna maybe “cross talking” on this. Anyone else have this problem ?

Finally once I put it all back together and fired it up it just ran, no popping at all, ran pretty good really but again the popping thing comes and goes, so I’m going to reserve declaring victory until I’ve been able to put some miles on it but with a couple of inch’s of fresh snow this morning and my looming knee surgery that may be a while, we’ll see.

So thoughts? Or inputs ?
Red 1976 oe owner
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
digger
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Re: Exhaust popping

#2

Post by digger »

I would make sure no air is getting into the exhaust, like a poor seal where the manifold bolts to the head. Check for or change out known good coils/wires if you might have others to try. A weak spark might cause this. I wouldn’t think carbs but again, if you happen to have an extra rack to try it might be worth it to see if there is any change. Does it pop any more or less if you give it some choke?
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CYBORG
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Re: Exhaust popping

#3

Post by CYBORG »

I agree with an air leak someplace. What does the plug color tell you? Might check the input clamps.
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Fred Camper
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Re: Exhaust popping

#4

Post by Fred Camper »

I think you are now unemployed regarding the Popping until it surfaces again. Sorry you lost your job, but that is just the way it is for now. I do think perhaps the crush washers under the headers may be too crushed but once again, you are unemployed and cannot check them yet.
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pidjones
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Re: Exhaust popping

#5

Post by pidjones »

Open exhaust or "boom tube" type can also cause popping in the exhaust.
"Love 'em all.... let God sort 'em out!"
Ex 2006 GL1800 - the Black Pearl SOLD! to make room for:
2021 Can-Am Spyder RT Limited Dark Chalk Metallic
1975 Red GL1000 project - ex Pistol Pete project
1972 Triumph T150V Trident rescue - finished and FOR SALE!
1976 Yamaha RD400c
1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
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gltriker
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Re: Exhaust popping

#6

Post by gltriker »

Remove the hot rodded carburetors. ;)
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redglbx
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Re: Exhaust popping

#7

Post by redglbx »

Digger, Cyborg & PID, I have factory exhaust and would add that if this was an exhaust leak I believe the “popping” would really be pronounced on deceleration but it doesn’t pop at all then,, only at idle. Not sucking any air in at idle. When I had the plugs out yesterday they were clean and looked pretty much perfect with the exception maybe of #1 which looked a little darker than the other 3.

Fred,,, thanks for the sentiments and condolences 😁

Cliff, how about some explanation of why or at least some kind of theory of what on these carburetors that have worked perfectly for over ten yrs now or what can be causing this popping with them. Just saying remove the “hot rod” carbs is like sayin it’s the air in the tires that’s causing the popping.
Red 1976 oe owner
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
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dontwantapickle
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Re: Exhaust popping

#8

Post by dontwantapickle »

Just today, I fired up a wing that has been sitting all winter and was cold.
It started easily, and after running a bit and idling with the choke off,
I noticed a slight popping coming from the left exhaust.
(Maybe it was more of a light chuffing / coughing that straight up popping).

Just lightly touching the synch adjuster on the #2 with my finger stopped the popping.
I took the bike for a ride and after warming it up completely, there was no more noise.

I'm figuring that the carb synch may need to be looked at.

My issue might be your issue - might not.
redglbx
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Re: Exhaust popping

#9

Post by redglbx »

Thanks Don, after my knee surgery this week I’ll have to take a look, I haven’t looked at the sync for quite some time now, other than the popping (mine has the chuffing and definite popping) mine just has been running so well & strong that I haven’t really done anything , maybe it’s time.

The more I think about this since doing the compression & leakdown tests the other I’m kinda thinking that the Dyna may be cross talking between the modules somehow. If the popping returns I’m thinking of just changing the Dyna unit out ,,,,, we’ll just have to see, thanks for the thoughts Don.
Red 1976 oe owner
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
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pidjones
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Re: Exhaust popping

#10

Post by pidjones »

How is the knee so far? My right meniscus may have torn about a month ago. I am finishing up a kick-start Triumph T150V Trident plus I have a Yamaha RD400c that I love riding. A couple month layup fo surgery recovery is Okay, but hoping not to loose that ability permanently. I had a '78 that popped a bit when first rescued, but cleared up and sounded fine after 100 or so miles. A loose connection in the coil supply, kill switch, any of that circuitry might cause a misfire. Mine was points and I suspect one of the connections (all cleaned and tightened during the rescue) was marginal. I know the kill switch was mechanically failing, as it fell apart on the next owner (a friend) but we were able to perform a good repair on it.
"Love 'em all.... let God sort 'em out!"
Ex 2006 GL1800 - the Black Pearl SOLD! to make room for:
2021 Can-Am Spyder RT Limited Dark Chalk Metallic
1975 Red GL1000 project - ex Pistol Pete project
1972 Triumph T150V Trident rescue - finished and FOR SALE!
1976 Yamaha RD400c
1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
Ex '79 CB750F rat bike
Ex '86 SEi
Ex '77 GL1000
Ex '76 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped
redglbx
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Re: Exhaust popping

#11

Post by redglbx »

PID, I had my same left knee repaired about 15-18yrs ago and quite frankly it was no big deal, I was up and walking unassisted a day or two later and was fine within a month, Dr this time just made a point of telling me no kneeling on it for at least 2 months.

This time around it’s been going on for about 4yrs but I’ve been unable to address it because of the severe back problems, that surgery was in 2021 and required 2 months in the hospital due to near death experience and now we’ve gotten to where the knee can be Address’d. The Dr’s happy because the knee is structurally sound so it is only needing the meniscus repaired.

The funny thing about the meniscus is that it can heal itself, mine is way better than it was a couple of months ago but about the time I start thinking to maybe cancel the surgery it gives me a serious shot of pain. So we’ll just get it fixed and hopefully get another 15+ years out of it, prolly be dead by then anyway. The bad thing about the knee problem which causes me to walk funny (funnier than normal) and it agitates the heck out of the back which I seriously do not want to revisit.

Anyway I wouldn’t sweat it with your knee, you should be fine and be able to ride normally, only may need to stretch some over distance. I was able to do 1000mi rides on my 14 FJR after my knee repair but you may see me stretching things going down the Highway, post back surgery I really can’t ride more than about 100mi before I have to get off so my days of distance riding are done.

All this is in part why I’ve been trying to get my red 76 at 100% because it’s a lot lighter than my FJR and with the really low c/g it’s not at all top heavy like the FJR, we’ll get there.
Red 1976 oe owner
1976 LTD restored
1980 CBX , in the que, to fix the ignorant heavy handed owner
1981 CBX
1977 CB750 K7
2014 FJR OE owner, sold
1980 GL1100
1984 GL1200 naked
1969 CL350, in the que
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