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Popping on Decel and Idle

15K views 31 replies 12 participants last post by  CombatMedic 
#1 ·
I wanted to throw this out there and get everyones opinion to see if we are on the right track.

My uncle (the one that I bought the bike from) and I have been riding and we are trying to resolve a popping issue that I am having with my exhaust. It is only when I release the throttle and when I am idling. Also the Left pipe seems to be a little blue indicating an incorrect mixture.

Here is what we were thinking.

  • Replace the exhaust gaskets
  • Re-jet the carbs. He has some or knows where to get some that will work.
  • I was also going to get some pipe wrap and wrap up my pipes.
What do you guys think. I am still new at this. Any other alternatives or suggestions are always welcome.
 
#3 ·
Welcome
I find that Pop, pop, pop Pleasing...
I can control it too...
IF - When slowing with engine compression, I hold the throttle closed while slowing it does NOT pop,pop,pop,pop,.BUT IF I leave it cracked open slightly It`ll Pop,pop,pop,pop, to my liking...


Try it and SEE for yourself...
Then PLEASE report back, so as I know I ain`t crazy;)


Lets RIDE (pop,pop,pop)


WELCOME
 
#5 ·
Welcome
I find that Pop, pop, pop Pleasing...
I can control it too...
IF - When slowing with engine compression, I hold the throttle closed while slowing it does NOT pop,pop,pop,pop,.BUT IF I leave it cracked open slightly It`ll Pop,pop,pop,pop, to my liking...


Try it and SEE for yourself...
Then PLEASE report back, so as I know I ain`t crazy;)


Lets RIDE (pop,pop,pop)


WELCOME

Oh Captain-D you may still be crazy.....but I do know what you mean as I have done that as well. You can control the popping at times by how much throttle is being shut down.......Or maybe I'm crazy too? :smile2:
 
#7 ·
The pipes are not stock. They have been changed. I think that the gaskets were not replaced at the time so I think that may be one of the problems.

I have slightly adjusted the idle knob. It is set about 1100 RPM on IDLE with no Choke.
 
#8 ·
That sure is an interesting concept of pushing the throttle more closed. I wouldn't think that was possible but with the dual cable system on the throttle it must help hold the butterflies tight. I will have to try that to control some of my decel pop with aftermarket pipes.
 
#10 ·
On mine I have the mixture screws out about 3 1/2 turns, and it still pops on decel. It has after market pipes which i have resealed. My theory is that with the stock exhaust there is an expansion chamber between the 2 pipes that allow exhaust gasses to equalize somewhat and cushion the flow and quiet the popping. Now there is now crossover between the pipes.
In the old days when guys would put dual exhaust on their old cars with a single exhaust, the shop would weld a crossover pipe between, to help stop pop backfire.
 
#11 ·
Another thought I have had about this decel pop so many guys have talked about, and I have too, on my '83 750. I had old 1960's 305 Hondas and they were 2 cylinders and dual exhaust, and I don't remember any pop. So many other bikes with a single pipe per cylinder and they don't pop. My neighbor has a Suzuki 500 and it doesn't pop. Another guy has a Kawa KZ1000, and no pop.
So why do so many of these bikes have this issue???

Here is may theory on this also=
I believe it is complicated by the dual spark system which fires a plug on the exhaust side also. My manual shows only one signal plate for the crankshaft to signal the pulse generators. So EACH revolution of the crank it can fire the coils which of course fires 2 plugs on each side of the cylinder. There is no cam sensor,( but later bikes have them), so the ignitor probably fires each revolution. So on decel there is more chance of exhaust burning off than with a conventional 1 plug one spark per power stroke system. I haven't proved this yet and maybe somebody else here has experimented with this.
 
#12 ·
No, what you guys need to do is video the SOUND so that we can say if its normal or not. Youll ALWAYS get noise in decel which is normal, and some may be confusing this with 'popping'.
 
#14 ·
I do believe this IS normal for these engines because of the spark system. I never hear cars do that on decel because there is no spark in the cylinder except for the normal spark timing.. If I am correct, at least on my year and model, it fires every revolution, so more chance to fire off the excess fuel out the exhaust. And this may very well be the intent of the factory to control some of the emissions. On the older bikes I had with points it was timed off the cam and fired only when at TDC power stroke. This system is only timed off the end of the crank for every revolution.

Just throwing out what I have seen so far and hope some engineering minds will correct or agree with this.
 
#15 ·
Hey guys,

I'm going to be replacing the crush gaskets tonight on my bike after work (02 ACE 750), but need to know what size the bolts holding the muffler on are. Does anyone know off the top of their head? I recently relocated for work and don't have any of my tools with me. That leaves me to rent a torque wrench and buy a socket at the local autozone. I figure a single socket (the correct size, of course) would be far cheaper than a set (duh!).

Anyone know?

TL,DR: What size socket do I need to remove the exhaust from a 2002 Honda Shadow ACE 750?
 
#16 ·
I have an older bike but I think most are 10 MM heads on the nuts, with a 6 MM stud.
I have to use a swivel 10MM socket 1/4 inch drive to get to a couple of mine but maybe your pipes are not as tight of a bend.
 
#17 ·
By the way, today I went for a good ride and tried the trick of closing the throttle tighter to try to slow the pop, pop. But it didn't help,it may be my cables are looser. I don't mind the pop all that much anyway.
 
#19 ·
Got around to getting the pipes off to replace the gaskets - turned out to be 12mm acorn nuts. It was a complete bit@h getting those dang things back on, though. You really have to finesse the thing back on to get everything seated the right way. I'll write another update tomorrow evening - the gasket sealer directions say to let it cure for about 24 hours before getting it back up and running.
 
#20 ·
So the pipe gasket change didn't really do too much for the popping, unfortunately... But this weekend I was able to run a can of seafoam through the tank (lots of holiday riding) and she seems to sound a lot better. I also took the idle jet screws out to 2.75 turns (from 2.25). I'm guessing the carbs had some gunk in the jets that just needed a light cleaning to get back to 100%. I'll keep listening for more popcorn and backfiring, but so far so good! :)
 
#21 ·
Don't know if this would apply to your bike or not, but on my vt1100c2 my popping/backfiring had 2 causes. The first was the crush gasket on the front cylinder was not sealing (p.o. hit exhaust on trailer right after he got bike and never fixed it!). I replaced both of those crush gaskets and that stopped the backfiring. However the popping on decel for me at least was caused by the pilot jet being partially blocked. Seafoam did not help in my case. The actual fix ended up being tearing down the carbs for a good cleaning, checking everything and replacing my stock #42 pilot jet with a #45 pilot jet and syncing the carbs. My bike has popped 1 time in the months since, this has been in around 3,500 miles.
YMMV
 
#23 ·
I think you guys are confusing regular decel noise for 'popping' and are not hearing the actual random popping caused by the lean condition/pair valves.

Which is why i keep asking for a video.
 
#27 · (Edited)
Here's the deal. If your head to pipe sealing surfaces are not all gouged up and are in good shape, your best bet is to just clean them up with some brake clean or a strong solvent of your choice and just use the crush gaskets. No other sealer is needed. If you have some gouges or small scratches/cracks then you have to go to plan B. I would not worry about what's there already and I would not replace the gaskets just yet. See if leaks occur over the next few weeks and then react. I always keep a spare pair of crush gaskets on hand because I seem to go thru them with experimentation.
 
#30 ·
It is very common especially with aftermarket pipes. If they have a cross-over tube welded between then that helps.
 
#31 ·
If it runs decent it could still be a little crudded up. Stock pipes, adjust screws to 2 3/4 turns and run some Seafoam thru your tank a couple times. I wouldn't pursue any other avenues until I tried these remedies 1st.
 
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