Popping noise

[Zaphod42]

I had my favorite shop change out the SVs exhaust a few weeks ago. The new can (Two Bros) sounds awesome & looks great, but I’ve noticed a lot of popping when I let off the throttle and sometimes during up shifts.

Is this a bad thing, or something unique to a V-twin? Any idea whats going on?

Thanks!
~Zaphod

[stringzz]

Are you referring to back fires? I hear them now and again on my Yosh Slipon. I would imagine it would have to do with more flow on the exhaust but not up front, ie new air filter and re-mapping.

That is a wild guess, the experts here can correct me ;)

[vertis]

My exhuast is stock, but I've read some posts here by other people with the same problem that did this (http://www.holeshot.com/sv650/decel.html).

There's a few threads if you search.

[racinteach]

has to do with the cold injection..PAIR valve system. You'll hear it more on colder days then hotter days.....personally I like the popping sound....:D

[TheKillerSV]

Originally posted by racinteach
has to do with the cold injection..PAIR valve system. You'll hear it more on colder days then hotter days.....personally I like the popping sound....:D

+1 :D

[Zaphod42]

Thanks!

I like the popping sound too ;)

I was just a little worried something might have been wrong with the bike, or something might get dammaged.

Y'all rock!

~Zaphod

[Kyoseki]

The backfiring can occasionally blow a throttle body off on the 1000, don't know about the 650, it's more of a pain in the ass than anything serious.

I disabled my PAIR, I haven't got around to removing the whole system yet.

[asdfbeau]

Taken from a wikipedia entry on backfiring...

"Backfire in an automobile engine typically results from various malfunctions related to the air to fuel ratio. Usually, backfiring occurs in carbureted engines that are running lean where the air fuel mixture has insufficient fuel. ("Running lean" is typically a sign of mal-adjusted carburetors or fuel injection where there is not enough fuel for the amount of air).

Backfire also occurs in engines that have an exhaust leak.
When a driver shifts up and lets off the gas, the engine has a moment of running rich or with insufficient oxygen. This causes an incomplete burn which causes the fumes to explode in the exhaust system. The leak itself is the most dangerous aspect. Without it, the mixture would cool enough not to explode."

in this case, I believe that you close the throttle, but the engine is still sucking fuel from the carbs, which doesnt get completely burnt, and ends up 'pop'ing inside the exhaust system.

If you're really worried about it, you can just pull the spark plug from under your seat and it will tell you if you're too rich, or lean. My SV does it too, and it's running rich, but better to be too rich than too lean.

[pAint]

So plug or no plug? That is the question..

[Zaphod42]

"...plug or no plug..."

I went looking for a 3/8 rubber plug this evening, and couldn't find anything other then a 3/8 rubber "vacuum cap." That was Kragen. Nappa was closed. I'll try again tomorrow.

The "Holeshot" instructions makes the job look VERY simple. Might try one of the caps in the morning before riding to work. Otherwise I'll just look around again for a proper "plug."

I hope to ride up the coast to the Lompoc area (Vandenberg AFB) Thursday or Friday, and want the bike runnin' as smooth as possible ;)

I'll keep ya posted~

[NiteQwill]

Originally posted by Zaphod42
"...plug or no plug..."

I went looking for a 3/8 rubber plug this evening, and couldn't find anything other then a 3/8 rubber "vacuum cap." That was Kragen. Nappa was closed. I'll try again tomorrow.

The "Holeshot" instructions makes the job look VERY simple. Might try one of the caps in the morning before riding to work. Otherwise I'll just look around again for a proper "plug."

I hope to ride up the coast to the Lompoc area (Vandenberg AFB) Thursday or Friday, and want the bike runnin' as smooth as possible ;)

I'll keep ya posted~
You don't need a 3/8" plug... a 1/2" works just fine, that's what I use. Don't need an autoparts store either, try Ace, Home Depot, Lowes, etc.

[pAint]

Are there any benefits performance wise to plugging this?

[Kyoseki]

Originally posted by pAint
Are there any benefits performance wise to plugging this?
No, nor is there any gain from leaving it in.

The only performance gain you can get from the PAIR system is removing it to make the bike lighter.

[Zaphod42]

"The only performance gain you can get from the PAIR system is removing it to make the bike lighter."

... and less "popier' :note:

[copperdopper]

so if its a useless peace why is it there....???
just curious

[NiteQwill]

Originally posted by copperdopper
so if its a useless peace why is it there....???
just curious
Why is what where?

Talking about the PAIR system? If so, it's for emissions regulations.

About the plug? To prevent backfire and like said above, on anything larger than a 650... you may blow the TBs.

[Currently]

To burn unburned hydrocarbons to help with emmisions.

Like everyone else here ... like that gurgling/popping noise!

Hey, I paid a lotta money for that effect and I will enjoy it!

[Zaphod42]

Couldn't find a "plug" at any of the local hardware or auto parts stores, so I improvised.

Took one of the vacuum caps purchased at Kragen, and instead of just covering the top of the T connector, I slid the bullet shaped cap up into the hose, reconnected the hose to the T connector then went for a ride.

It worked like a charm. No more backfiring! Now it sounds less Harley and more Ducati~ but better, since the SV doesn’t need valve adjustments every 6K miles ;)

Thanks again!:worthy:

~Zaphod