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Discussion Starter · #1 ·
I know this is a popular topic, but I was not able to find a simple answer to my question.

My new (to me) 02 750 ACE has Cobra pipes on it. The sound is great! The bike runs like a top (cold blooded on startup).

My question is: is popping normal on decel?

This is not a backfire crack, just popping. If not, should fuel adjustment be made? I'm not inclined to add a jet kit.

Thanks
 

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I ran into this with another Honda. My VTX had Cobra pipes installed when I purchased it. It popped a lot riding with steady throttle or while decelerating. I had to do a lot of research but I finally corrected the problem.
I learned as a teenager that a leaky exhaust system would cause a deceleration popping condition due to the air leaking in and causing the unspent gasses to ignite inside the system.
Honda installed a fresh air injection system to cause those gasses to continue to burn, thereby reducing emissions a little. To counter the popping, they installed a balanced exhaust system with just enough back pressure to inhibit popping.
Guys like me and you buy the bikes and want them to sound better, so we change the exhaust systems. They're no longer tuned, and they pop.
To eliminate those unburned gasses, we would have to lean the mixture a lot. Probably more than we really want to, and the valves could suffer.
The alternative is to eliminate the fresh air. A reed valve is installed on the top of each valve cover. A hose attached allows fresh air in. The hose is attached to the PAIR valve and it gets it's input from the filtered side of the breather. You can either plug the single inlet hose (which is what I did.) or you can remove the system altogether. This will eliminate popping. It will also dirty up your emissions some. I don't have any idea if this goes against any EPA laws or edicts, but it sure makes the bike sound better. While the VTX is a completely different model, the system is the same. bareasschoppers.com has information. Google "VTX Desmog" and you should find plenty of information to help explain. I eliminated fresh air from my exhaust system and eliminated ALL popping.
 

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The alternative is to eliminate the fresh air. A reed valve is installed on the top of each valve cover. A hose attached allows fresh air in. The hose is attached to the PAIR valve and it gets it's input from the filtered side of the breather. You can either plug the single inlet hose (which is what I did.) or you can remove the system altogether. This will eliminate popping. It will also dirty up your emissions some. I don't have any idea if this goes against any EPA laws or edicts, but it sure makes the bike sound better. While the VTX is a completely different model, the system is the same. bareasschoppers.com has information. Google "VTX Desmog" and you should find plenty of information to help explain. I eliminated fresh air from my exhaust system and eliminated ALL popping.
Do you know if this is also the case on the Spirit 750s? I installed the Cobras on mine, and got the popping, but ONLY on decel. Steady throttle has NO popping. However, I've been planning on doing the jet kit anyway, when I install my chrome spike K&N-type air cleaner, since I will need to do that. Had the $ almost all saved up to do that, when a friend needed some help, and then he disappeared, so I haven't got it back.
 

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Discussion Starter · #5 ·
Wow, this is getting lively! Thanks for the input...I'll look into this.
 

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We got my wife a Spirit 750 and that was after doing the modification to my VTX. Looking over the Shadow I noticed that it indeed had the same reed valves on top of the cylinder heads and the same PAIR valve. While I haven't read anything on this subject, I'm sure the popping would be present on this engine just as it was on my VTX. It seems like such a waste to expel so much unburned fuel out the exhaust pipes, but for now I guess that's just what we've got to deal with.
 

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We got my wife a Spirit 750 and that was after doing the modification to my VTX. Looking over the Shadow I noticed that it indeed had the same reed valves on top of the cylinder heads and the same PAIR valve. While I haven't read anything on this subject, I'm sure the popping would be present on this engine just as it was on my VTX. It seems like such a waste to expel so much unburned fuel out the exhaust pipes, but for now I guess that's just what we've got to deal with.
They could always install a catylitic convertor.:-(
 

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My money is on you needing a bigger slow jet. Adjusting your a/f mixture can make it pop less. If it's cold blooded and the popping only happens when you decel, but it runs fine otherwise, it's gonna be the slow jet...which doesn't come with a rejet "kit," at least not the dynojet kit that I used. I had to buy a new slow jet, available individually through Jets r us, after cutting the baffles out of my exhaust and desnorkeling my airbox.
 

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If the bike is new to you, I would suggest you start with a full tune-up. Start with a new air filter, plugs, oil change & filter, fuel filter. Once that is done, start tuning your carbs. There is no sense changing the A/F on the carbs until you know the state of your air filter & plugs.

Have your carbs been drilled to adjust? This would be an easy indication that someone has already changed something. If not, you're running stock A/F mix and with new pipes you will have popping.
 

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If it was never jetted for pipes I agree with your plan. Often simply backing out the air/fuel mixture screws a quarter turn at a time may solve it. Any more than 3.5 turns out with no resolution to the popping and a rejet is your only recourse.
This.

I ran into this with another Honda. My VTX had Cobra pipes installed when I purchased it. It popped a lot riding with steady throttle or while decelerating. I had to do a lot of research but I finally corrected the problem.
I learned as a teenager that a leaky exhaust system would cause a deceleration popping condition due to the air leaking in and causing the unspent gasses to ignite inside the system.
Honda installed a fresh air injection system to cause those gasses to continue to burn, thereby reducing emissions a little. To counter the popping, they installed a balanced exhaust system with just enough back pressure to inhibit popping.
Guys like me and you buy the bikes and want them to sound better, so we change the exhaust systems. They're no longer tuned, and they pop.
To eliminate those unburned gasses, we would have to lean the mixture a lot. Probably more than we really want to, and the valves could suffer.
The alternative is to eliminate the fresh air. A reed valve is installed on the top of each valve cover. A hose attached allows fresh air in. The hose is attached to the PAIR valve and it gets it's input from the filtered side of the breather. You can either plug the single inlet hose (which is what I did.) or you can remove the system altogether. This will eliminate popping. It will also dirty up your emissions some. I don't have any idea if this goes against any EPA laws or edicts, but it sure makes the bike sound better. While the VTX is a completely different model, the system is the same. bareasschoppers.com has information. Google "VTX Desmog" and you should find plenty of information to help explain. I eliminated fresh air from my exhaust system and eliminated ALL popping.
Not this.

Do you know if this is also the case on the Spirit 750s? I installed the Cobras on mine, and got the popping, but ONLY on decel. Steady throttle has NO popping. However, I've been planning on doing the jet kit anyway, when I install my chrome spike K&N-type air cleaner, since I will need to do that. Had the $ almost all saved up to do that, when a friend needed some help, and then he disappeared, so I haven't got it back.
Yes, its a thing. The Shadows come really lean from the factory so you have to richen it back up a bit after leaning it out from the freer pipes.
 

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My money is on you needing a bigger slow jet. Adjusting your a/f mixture can make it pop less. If it's cold blooded and the popping only happens when you decel, but it runs fine otherwise, it's gonna be the slow jet...which doesn't come with a rejet "kit," at least not the dynojet kit that I used. I had to buy a new slow jet, available individually through Jets r us, after cutting the baffles out of my exhaust and desnorkeling my airbox.
You dont 'need' to rejet unless you mess with the airbox.
 

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FYI - my 750 has Cobra Streetrods (full length), stock air box & jets. It originally popped on decel, slight popping on constant throttle. I tried to back my A/F screws out to fix it, and had it pretty close, but after having it tuned up by a shop it runs better than ever. I'm pretty sure my old air filter was preventing me from ever getting it right.
 

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You dont 'need' to rejet unless you mess with the airbox.
This may be true with newer bikes; I dunno.
But not true for the 1100 A.C.E. like mine & Harryc's.

I respectfully, totally, diametrically disagree with our peer & cohort Furball Zen.
I will admit to minimum dealings with the lil' 750's, like the OP has....the only one of those here is bone stock all over, plus FI instead of carbed.

But the VT1100C2 A.C.E.'s are a different critter.
If you change from stock pipes? You inherit a popping problem....verified by about 6 other owners with the same issue / same fix.

Mine has stock airbox & stock air filter setup.
V&H pipes; WFO & loud.
A/F mix helped with popping on decel, but the Dyno Jet kit was the fix.

I'm a decent shadetree mechanic, but getting a real tuner made another big difference. Kenny reworked it and WOKE IT UP.

Worth every dime.

Try everything else first, then get the kit.

Otherwise: you're postponing The Inevitable.
And the bad thing about The Inevitable?
It ALWAYS happens!

Glad I bought the Dyno kit. The increased "Comes Outta The Corner Like A Bitin' Sow!" alone, is worth the cost.
Losing the pop is just a fringe benefit.
 

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Nah.
But if you came to visit, he is only 25 minutes away!

Before he reworked the carbs, I THOUGHT I was pretty good....after all these years.

But I'd been wrong before....
 

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This may be true with newer bikes; I dunno.
But not true for the 1100 A.C.E. like mine & Harryc's.

I respectfully, totally, diametrically disagree with our peer & cohort Furball Zen.
I will admit to minimum dealings with the lil' 750's, like the OP has....the only one of those here is bone stock all over, plus FI instead of carbed.
Then how can you disagree with someone who had a 750 for 8 years and 26000 miles and did all the work on it?
 
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