Bike pop on decel, increasing main jet would do any good?

[gsf500RR]

Hi

At first I installed a K&N lunchbox on my 2006 GS500 IXIL exhaust and I rejetted with:
*dinojet needle (from dinojet stage 1 kit http://www.dynojet.com/pdf/3156.pdf)
*140 main jet
*18 pilot jet
Result: bike work very good but pop hard on decell.

So I changed the 18 pilot jet for a 27.5
Result: the bike doesn't pops on decel anymore unless I close the throttle at high rev (>6-8K rpm) 


So what do I do now to stop pops when decel at high rev?
I've tried playing with the turns out and the needles washers but no result.


Should I try upgrading the main jet to a 147.5 or it would be useless?

[jestercinti]

First off, the Dynojet needle should have clip settings.  The clip settings do the same as washers under the stock needle.  Raising the needle enriches the mixture for midrange RPM.

18 pilot to 27.5?    Way to much just knowing what you posted.  Normally, you increase the pilot 1, raise the needle, and increase the main jet several sides.  140 seems a bit lean on your setup for the mains.  I'd try 147.5 or one in between if you have it to see what the difference is.

Your pilot is too rich.  Go back to 18, and try 147.5 and see what happens.  Fine tuning the needle clip by raising it should work for the midrange RPM.  Also, the needle in the Dynojet kit is more aggressively tapered than stock, so these settings will be a bit different than stock needle comparisons in the Wiki matrix.

[Funderb]

upping the pilot jet a little is good, but that was way too much. you have a mid jet, which overlaps the pilot and needle range, in order to make tuning easier and more complicated at the same time.

The main jet wont help anything here. When you pop on decel, your throttle is closed, therefore, no low pressure over the emulsion tube. You need to adjust the fuel/air mix screw to improve popping and idle.

and, its going to pop on decel from high revs, get used to it.

[gsf500RR]

thanks guys for the help and sorry my english   

First off, the Dynojet needle should have clip settings.  The clip settings do the same as washers under the stock needle.  Raising the needle enriches the mixture for midrange RPM.

I have played with clip before upgrading the pilot jet with no result,  it would make make barely no difference in the way the bike would pops 

18 pilot to 27.5?    Way to much just knowing what you posted.  Normally, you increase the pilot 1, raise the needle, and increase the main jet several sides.  140 seems a bit lean on your setup for the mains.  I'd try 147.5 or one in between if you have it to see what the difference is.

Yes, I went from 18 to 27.5!

I did so because mitch79  had the same config as me and tried the 22.5 but it would still fart a little (on low rev closing throttle) and next jet was 27.5 so I decided to give it a try. And the fact is that it do not fart AT ALL anymore when I close the throttle (under 6k rpm).



Your pilot is too rich.  Go back to 18, and try 147.5 and see what happens.  Fine tuning the needle clip by raising it should work for the midrange RPM.  Also, the needle in the Dynojet kit is more aggressively tapered than stock, so these settings will be a bit different than stock needle comparisons in the Wiki matrix.

You mean lowering the clip right? I'm definitively not going back on 18!! On 18 the bike would pop a lot. I will try the 22.5 but not the 18!

upping the pilot jet a little is good, but that was way too much. you have a mid jet, which overlaps the pilot and needle range, in order to make tuning easier and more complicated at the same time.

Ok but with 27.5 the bike run perfect (accelerate like a rocket) and don't pop on decel unless I'm shutting throttle at high rev....

The main jet wont help anything here. When you pop on decel, your throttle is closed, therefore, no low pressure over the emulsion tube. You need to adjust the fuel/air mix screw to improve popping and idle.

Ok so the main jet wont help anything (this was the question I was asking myself). But would you still advise me like jestercinti to try the 147.5 because 140 should be to lean?

and, its going to pop on decel from high revs, get used to it.

Oh, I don't care about the pop on decel per se. What I care about is nothing destroying my engine, and I've been told numerous time that poping hurt the engine. It may take thousand of miles but show effect but it will have consequences.

And if only pop a little I wouldn't care anyway. But right now, when I close the throttle a 11rpm on third gear... it's like there machin gun shooting in my exhaust.

Should I try config:

22.5 pilot
147.5 main jet
clip on the lowest position on the needle
3 turn screw

?

thanks 

[Kijona]

It depends on what kind of popping you're talking about...

Does it pop if you free-rev (revving in neutral) the motor? Is this the popping you're talking about?

Or does it only do it when you downshift?

Popping on downshifting is normal for an aftermarket can. Kind of like cars that have glass-packs or cherry bombs or whatever you want to call them.

Popping when revving in neutral is not. It indicates a lean condition. It also may indicate messed up valve tolerances, among other things. You may wish to check that out as well.

[jestercinti]

Should I try config:

22.5 pilot
147.5 main jet
clip on the lowest position on the needle
3 turn screw

thanks 

That sounds like a better config to me.  Now, my only concern is that the bike may be a bit rich on the mids (i.e. needle too high), but you'll have to test this out and see.  If it seems a bit flat, try lowering the needle position.  If it gets worse when you do that, up the mid jet by 1.  There is most likely no mid jet in the DJ kit.  Stock on a 2006 is 60.  You can go to jetsrus.com and pick up the next size jet, 62.5, for under $4 a piece IF the needle setting is not working on the lowest clip setting.

Again, jetting is a black art.  What works for me may not be what works for you.  It all depends on elevation, config, air temp, humidity, etc.  You are definitely on the right track. 

I also will agree that some decel popping is normal on an aftermarket pipe.  Stock pipes are meant to squash those sounds, per government noise requirements.  Some stock pipes also have catalysts which "burn off" unburnt hydrocarbons too. 

If you have the PAIR system, this will cause popping...by design.  It sends air into the exhaust chambers to burn off any remaining unburnt hydrocarbons.  I can't remember if it started in 2007 or 2006.  If there are little pipes coming off of the exhaust side and head back into the engine, then you have it.  If you have the PAIR system you can always block it off.  That will help with popping a little, but the EPA may not like it if you live in an emissions area.  Search for it, there are threads that tell you how to do it.

[xunedeinx]

I'm at 22.5/62.5/147.5 with a K&N and a very free flowing pipe that ends under my right foot, and the idle is just fine. I popped in a 20 for curiosity sake, and it popped more. 22.5 should be the MAX you have to go, being you don't get much more free flowing than I am.

[gsf500RR]

It depends on what kind of popping you're talking about...

Does it pop if you free-rev (revving in neutral) the motor? Is this the popping you're talking about?

Or does it only do it when you downshift?

Popping on downshifting is normal for an aftermarket can. Kind of like cars that have glass-packs or cherry bombs or whatever you want to call them.

Popping when revving in neutral is not. It indicates a lean condition. It also may indicate messed up valve tolerances, among other things. You may wish to check that out as well.

It pop when revving in neutral  I checked the valve clearance. No problem!