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Backfiring during engine braking

I had the same issue with my FZ1 when I replaced the slip-on with a Yoshimura. I removed the fresh air induction system and the popping went away.
 
afm199 said:
Dude. That is why I said "UNLESS YOU ADD TEN PLATES". I used to run Supertrapps with twenty plates and an open end cap. Yes, the more plates you run the leaner the mix is, the louder and more likely to backfire.

how many are you running, what size mains, pilot jets do you have, and what air filter?
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sorry should've read that closer :shocker
 
you probably need to rejet to make the most of the new exhaust anyway.
The popping is most likely one of two things you could have an exhaust leak at the head where the pipe bolts up if you changed the head pipes if not check the seal at the pipe to can. but more likely as others have said your probably lean on your pilot jets try upping them by one size if it doesnt eliminate the problem but minimizes it up the jets two sizes. I would do some plug chops also if you are lean in the mid range or top end you could over heat the motor and damage it running too lean. little bikes tend to get run pretty hard and on the main jet a lot so id recomend a thourogh jetting project. the manufacturer of the pipe may have some ball park recomendations for jetting. keep you old parts smog inspections ar eon the way and you will need to return it to stock to pass if the bikes new enough to need a smog inspection.
 
elskipador said:
not usually. its actually from running lean & its called an afterburn, not a backfire. when you close the throttle from the upper rpm's the bike goes onto the idle/pilot circuit. this causes the exhaust tract & pipe to heat up really quickly & ignite unspent hydro-carbons in the exhaust. twins, as a breed, tend to like the lower rpm's a little on the rich side so the op could adjust his fuel screws. usually 2.0~2.5 turns out, for a slip-on & stock headers/airfilter will fix it. just remember that it SHOULD pop, @ least a little, on decel. if it doesn't your idle/pilot circuit is to rich.
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Listen to the man; he KNOWS from experience!

Every time I've put an aftermarket (full) system on (never tried a slip-on), they are always slightly lean off idle, which causes backfires on decel. Richen it up on the idle circuit a little & see what happens. May only be a few turns of the idle screw...

If your lucky, done. :teeth :ride
 
Ive got this condition on my bike too. Its got aftermarket pipes. With both dbkillers in, i dont notice it, however, i now have only 1 in, and get those pops on decel only.

What about the lean mixture would cause those pops? Im missing something. Is it basically detonation? I thought detonation was associated with pinging and not exhaust popping?
 
jc2ducati said:
What about the lean mixture would cause those pops? Im missing something.
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elskipador said:
not usually. its actually from running lean & its called an afterburn, not a backfire. when you close the throttle from the upper rpm's the bike goes onto the idle/pilot circuit. this causes the exhaust tract & pipe to heat up really quickly & ignite unspent hydro-carbons in the exhaust. twins, as a breed, tend to like the lower rpm's a little on the rich side so the op could adjust his fuel screws. usually 2.0~2.5 turns out, for a slip-on & stock headers/airfilter will fix it. just remember that it SHOULD pop, @ least a little, on decel. if it doesn't your idle/pilot circuit is to rich.
Click to expand...
.
 
OP just need to replace the OEM piston return spring with one matched to the new exhaust system.


:p
 
Not sure about the 1st gen SV, but the second gen SV's have something called the PAIR system. It's an emission control that adds air into the exhaust system to help burn up and remaing fuel. On second gen's people can disable this system to get rid of it and it eliminates the backfire on aftermarket exhausts.
 
I have a Yoshi Exaust on my R6S it runs fine to me. Now i do want to get Power commander for it. How much does it usally cost to get It Dyno Tuned?
 
If you want to get technical, replace the stock SV pilot jets (115) with 117.5 or just turn the fuel screws out a half turn. But before you do that answer how many plates you are running on the SV, what airfllter and what mains. If you don't know that, then just throw money at it, sooner or later some of the dollar bills will partially clog up the airbox snorkel, richen the mixture and fix the problem.

however you probably have an air leak.
 
My SV did the same for about two years after putting on an M4 slip on. I recently adjusted my throttle positioning sensor and took care of the backfire on engine breaking and a little hiccup she had from idle every once in a while
 
Brown81 said:
Anyone? Bueller? Elskip???


(someone once told me it could be exhaust manifold gasket leak?)

:cool
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i'll need to know @ what rpm you're getting "on the gas" & how much you're openning the throttle.

Asphaultnaut said:
OP just need to replace the OEM piston return spring with one matched to the new exhaust system.
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if you're talking about the slide return spring, its a good tuning tool, but not for the rpm/throttle position in question. the slide needle only affects the middle rpm's.

Norbs said:
Not sure about the 1st gen SV, but the second gen SV's have something called the PAIR system. It's an emission control that adds air into the exhaust system to help burn up and remaing fuel. On second gen's people can disable this system to get rid of it and it eliminates the backfire on aftermarket exhausts.
Click to expand...
FYI most cali bikes come from the factory with this sytem in 1 form or another installed on them. there are several methods that are used to remove/disable it for the track.
 
elskipador said:
i'll need to know @ what rpm you're getting "on the gas" & how much you're openning the throttle.
Click to expand...

First off: It has carbs

It happens whenever I get back on the gas at just about any RPM above a couple thousand.

Basically, say I run up to 8,000 rpm, then close the throttle and let the engine come down while engine braking, as soon as I open the throttle it goes "BANG"! The more/faster I get it open the bigger/louder the bang seems to be.

If I sorta clutch it in and sloooowly feed it some gas I can avoid it, especially at lower rpms. Any ideas?
 
Brown81 said:
Any ideas?
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yeah, but you'll need to be way more specific than this...
Brown81 said:
It happens whenever I get back on the gas at just about any RPM above a couple thousand.

Basically, say I run up to 8,000 rpm, then close the throttle and let the engine come down while engine braking, as soon as I open the throttle it goes "BANG"! The more/faster I get it open the bigger/louder the bang seems to be.

If I sorta clutch it in and sloooowly feed it some gas I can avoid it, especially at lower rpms. Any ideas?
Click to expand...
you say that @ any rpm over a couple thou when getting on the gas it pops. so @ 4k "getting on the gas" makes it pop? @5?, 6?, etc... how much are you getting on the gas? opening the throttle 50%? 75? 100%?

then you've got the closed throttle on decel... what are rpms do you mean when you say "come down"? & exactly how much throttle are you giving it?

with carbs it could be a host of issues as each rpm range is controlled by 1 or 2 parts in the carb & knowing exactly which rpm & throttle opening will drastically reduce your tuning time.
 
How about the PAIR emission system? Doesn't that cause decel popping?

My Bandit popped really bad until I put a plug into the air intake line.

(BTW, I really have no idea what I'm talking about.)
 
elskipador said:
yeah, but you'll need to be way more specific than this...

you say that @ any rpm over a couple thou when getting on the gas it pops. so @ 4k "getting on the gas" makes it pop? @5?, 6?, etc... how much are you getting on the gas? opening the throttle 50%? 75? 100%?

then you've got the closed throttle on decel... what are rpms do you mean when you say "come down"? & exactly how much throttle are you giving it?

with carbs it could be a host of issues as each rpm range is controlled by 1 or 2 parts in the carb & knowing exactly which rpm & throttle opening will drastically reduce your tuning time.
Click to expand...

Thanks for the response. Let me try and be more specific:


I am riding in top gear on the fwy going 80-90. I then close the throttle completely. The bike winds down to whatever rpm. I then re-apply the throttle. It goes "Bang" right as the throttle is applied. I can not give a percentage other than to say it happens right as I open the throttle again.

It will basically happen at every turn apex if you were on a technical road.

If I were at 9,000 rpm and closed the throttle, letting the engine come down to say, 6,000 rpm, it would then pop as soon as I reapplied the throttle.


If I were at 7,500 rpm and closed the throttle, letting the engine come down to 3,500 rpm, it would then pop as I reapplied the throttle.


It doesn't seem to matter that much what rpm it is at when I do reapply throttle. It pops no matter what. Just pops louder and more aggressively the more the engine is loaded and the more throttle I am dumping open. In other words: If I wind it out and just completely shut the throttle, then yank it back open the pop will be bigger then if I were to gingerly feed it 5% throttle.


I can avoid the pop by clutching and feeding it slow clutch and throttle at the same time.


Sorry if my terminology is lacking! I appreciate the difficulty of online diagnostics! :thumbup


edit: I should clarify it only pops when re-applying the throttle after the engine decelerating. Not if I am just accelerating from a stop. Not if I am going up through the gears.
 
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elskipador said:
FYI most cali bikes come from the factory with this sytem in 1 form or another installed on them. there are several methods that are used to remove/disable it for the track.
Click to expand...
Yep, Kawasaki started this trend in 1983' if I recall correctly...

Fresh air in the pipe makes for better smog tests = richer jetting.
 
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