Popping noises coming down from high RPMS?

[joberly]

Pretty much explains it.... when I let off the throttle at high RPM's the exhaust starts popping, what causes this and what's a good shop to go to for service, in eastern MA? I hate that sound, I feel like an idiot riding around like this!

[stoinkythepig]

Can be "normal". Usually a sign of a lean condition or an exhaust leak. A quick fix would be to, uh, pull in the clutch...

[mattyr6]

what bike?

[lopycam]

Depends on the bike. Some yamahas have an A.I.S. system which pumps air from the air box into the exhaust. This is to reduce emissions. The popping is an "afterfire" occuring from unburned fuel, hot exhaust and fresh air in the exhaust. My R1 does it. Even did it when it was bone stock. I hope this helps.

Nathan

[joberly]

It's an F2 with a Micron can... so I assume this is normal, then? I have heard other bikes do it too but always wondered.

[lopycam]

Originally posted by joberly
It's an F2 with a Micron can... so I assume this is normal, then? I have heard other bikes do it too but always wondered.

On a F2, it sounds like a jetting problem.

Nathan

[VinceF2]

My F2 always popped a little coming down from high RPM's like that... even after tuned at NEM on the dyno and jetted etc...

[Karaya One]

The popping is a lean condition. Most likely idle mixture. However, you may have to go to a larger pilot jet.

You can adjust the idle mixture screws to help, but if that doesn't work you will need larger pilot jets.

[PatSV650]

... then I gotta ask... My '03 SV650 w/ a Yoshi race only slip on (no baffles) pops alot when comin' off high revs, especially on a downhill.. That's not lean is it? Just a characteristic of a loud pipe, right? I am running a Power Commander with a map specific for "open or un-baffled" exhaust and K&N filter.

P.S. Need someone to ride my bike for me, wanna hear how it sounds off the bike

[TLRMan]

Originally posted by PatSV650
... then I gotta ask... My '03 SV650 w/ a Yoshi race only slip on (no baffles) pops alot when comin' off high revs, especially on a downhill.. That's not lean is it? Just a characteristic of a loud pipe, right? I am running a Power Commander with a map specific for "open or un-baffled" exhaust and K&N filter.

P.S. Need someone to ride my bike for me, wanna hear how it sounds off the bike

Just a lean decel or airleak. No biggie. Does the SV650 have a PAIR system on it? That's the culprit if it has one...Just injecting air into the exhaust, and igniting whatever unburned fuel resides there. There is a simple and quick way to disable it.

[bbhzx10]

Many new bikes also have cleaner emmissions systems on them that can cause the popping when an aftermarket exhaust is installed. The system puts fresh air into the exhaust to help ignite any unburned fuel in the exhaust resulting in cleaner emmissions. if you have an aftermarket pipe on a bike with one of theese systems you can usually bypass the clean air injection inexpensively, but you have to find the info on your particular bike. Or just keep riding, if you don't mind a little noise.

[TLRMan]

Originally posted by bbhzx12
Many new bikes also have cleaner emmissions systems on them that can cause the popping when an aftermarket exhaust is installed. The system puts fresh air into the exhaust to help ignite any unburned fuel in the exhaust resulting in cleaner emmissions. if you have an aftermarket pipe on a bike with one of theese systems you can usually bypass the clean air injection inexpensively, but you have to find the info on your particular bike. Or just keep riding, if you don't mind a little noise.

Suzuki calls it the "PAIR" system....

[PatSV650]

If it's just noise, which I kinda like anyway, then I'll just keep on riding and letting people know I'm coming and scaring wild animals and agravating people on their cell phones as I scream past, etc etc

[guru_lou]

The problem with the SV is that, when you shut down the throttle from high rpms, there's no fuel there for it to burn as it decelerates. Maps are made for good fueling on acceleration, but few tuners look at what it's doing during deceleration. The PAIR system (port air injection) pumps fresh air directly into the exhaust ports, supplying more oxygen to the unburned exhaust gasses.

Without going into too much detail, save a copy of your map so that, if you're not happy with the result, you can always go back to it. Take the high rpm values at 0% throttle opening and add 5 or 10 to them and reload that map. It should be better. If it still pops, repeat the procedure and add another 5 or 10 counts. I wouldn't take it past 25.

Also, get a copy of the service manual and block off the hose going to the PAIR injection pump. I wouldn't advise removing it unless you are going to race the bike and need to remove a couple of extra pounds of weight. By blocking it off, you'll get rid of the extra air going into the exhaust ports which will reduce the popping. If you have to take the bike in for emission testing, it'll just be a matter of removing the block to get it to pass.

Another thing that this will fix is the off-on throttle abruptness that a lot of fuel injected bikes suffer from.

[TLRMan]

Originally posted by guru_lou
The problem with the SV is that, when you shut down the throttle from high rpms, there's no fuel there for it to burn as it decelerates. Maps are made for good fueling on acceleration, but few tuners look at what it's doing during deceleration. The PAIR system (port air injection) pumps fresh air directly into the exhaust ports, supplying more oxygen to the unburned exhaust gasses.

Without going into too much detail, save a copy of your map so that, if you're not happy with the result, you can always go back to it. Take the high rpm values at 0% throttle opening and add 5 or 10 to them and reload that map. It should be better. If it still pops, repeat the procedure and add another 5 or 10 counts. I wouldn't take it past 25.

Also, get a copy of the service manual and block off the hose going to the PAIR injection pump. I wouldn't advise removing it unless you are going to race the bike and need to remove a couple of extra pounds of weight. By blocking it off, you'll get rid of the extra air going into the exhaust ports which will reduce the popping. If you have to take the bike in for emission testing, it'll just be a matter of removing the block to get it to pass.

Another thing that this will fix is the off-on throttle abruptness that a lot of fuel injected bikes suffer from.

Hmmm...adding fuel at closed throttle positions.....Hey Gerard, sound familiar?
This also helps our EX NESR Racer's Bike be more transient from on-off throttle at the track..
One must remember to not put too much fuel into yer engines on decel, or you'll be looking at fouled plugs, and not a happy engine.
Works best during race conditions because of the higher RPM's.
The map should be to Zero values approximately 500 rpms above what idle rpms are, and your fuel economy will drop a touch if you do this.
A lot easier to just block off the Pair valve intake hose (at the airbox) with a 3/8" bolt.

[guru_lou]

Blocking off the PAIR supply helps, but is not the end-all anwer. You really do need to put some fuel in there also. To go to an extreme example, for H-D bikes we typically put anywhere from 25 to 40 at the 0% throttle position. Leave the numbers as they come out for the 0% throttle at the idle rpm +/- 500 rpm, i.e., if the bike idles at 1200 rpm, use the posted numbers for 500, 1000, and 1500 (and if you have a USB PC, do the same with the 250 rpm steps). At the rest of the positions, add the fuel. The engine is just transitioning thru that portion of the fuel map, so there's minimal chance of fouling the plugs.

For those with race bikes or more aggressive setups, it helps if you raise your idle by 200-300 rpm, on top of the info I gave you about the numbers. It'll make the off-on throttle transitions smoother.

I realize that most of you guys don't know me, or, in fact, some of you may but just don't realize it. My real name is Lou Alvarez and I live in New Ipswich, NH. I work part time at Roger Pageots shop, RJs Motorsports (shameless plug), in Nashua. I spend most of my time there taking care of the computer system for the shop and running the dyno for him. I've been doing the dyno work for a couple of years.

For those of you who were at the shop this past weekend for the Brian Paquette fund raiser, I apologize for not being available, but my real job took me out of town over the weekend. I've dynoed and tuned a lot of bikes over the past couple of years, and have fixed a lot of power commander problems from bad tuning done by owners and other shops. We've had a lot of happy customers at our shop and Roger is one of the best guys in the business, as anyone here who has dealt with him will attest.

I'll be happy to answer any bike related questions that deal with dynos and power commanders. If you want to email me offline, it's loua@varian.mv.com. If I don't know the answer, I'll tell you exactly that, not try to bluff my way thru.

[TLRMan]

Originally posted by guru_lou

Oh I can have a lot of fun with you!

[guru_lou]

Bring it on!