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Discussion Starter · #1 ·
2003 SV 1000 7861 miles
Sometimes when I come off of idle get a backfire. Just a bang that’s it ,Like at a traffic light. My idol is set at 1300 RPM. I have checked the throttle positioning sensor and it’s right on the money. I run 93 octane ,Could there be a vacuum leak. That could cause this.It doesn’t happen all the time. Just every once in a while . That’s why I have my doubts if it’s a vacuum leak cause it would be consistent. As well as anything mechanical ,Can’t think of anything else. New air cleaner as well as everything else is new.
Tire Water Sky Wheel Plant
 

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A random misfire on shutting the throttle ?? That's very common with singles and twins. Nearly all my bikes are 1 and 2 cyl, and they all do it. My 4 cyl like my GSXR and the Eliminator are going to do that only when you fit those with really really unequal length exhaust pipes. My eliminator that had those now sold 15+ yrs was fitted with a crazy exhaust with totally unequal length and some tight compression bent exhaust pipe, and it sounded like an ak47 when you snap the throttle shut. The GSXR sounds fine, its just got a proper D&D system on it.
 

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Discussion Starter · #3 ·
A random misfire on shutting the throttle ?? That's very common with singles and twins. Nearly all my bikes are 1 and 2 cyl, and they all do it. My 4 cyl like my GSXR and the Eliminator are going to do that only when you fit those with really really unequal length exhaust pipes. My eliminator that had those now sold 15+ yrs was fitted with a crazy exhaust with totally unequal length and some tight compression bent exhaust pipe, and it sounded like an ak47 when you snap the throttle shut. The GSXR sounds fine, its just got a proper D&D system on it.
No not when shutting down,, you’ll be sitting at a light .and when you give it gas every once in a while you get a Bang..
 

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Disturbed, very...
2003 SV1000S
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1,900 Posts
Do you have the PAIR valve eliminated, or at least blocked off ?

With aftermarket cans, the lack of back pressure allows a lot of air "pockets" for want of a better discript to pass through, with unburnt fuel just itching to get that fresh air....
generally gives annoying popping and banging on the overrun, but, if the bike is running rich enough......pop bang...
 

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No not when shutting down,, you’ll be sitting at a light .and when you give it gas every once in a while you get a Bang..
I didn't mean when shutting down. I meant when you close the throttle especially when under load and you go from accelerating or steady speed to engine braking. but you're getting it under no load just sitting and revving. That's not what I'm referring to. Is it related to a specific throttle position ?
 

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KNEE DRAGGER
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No not when shutting down,, you’ll be sitting at a light .and when you give it gas every once in a while you get a Bang..
Some of this you have said you did but I will list the items that have cause what you talk about in several SV/DL1000 I have repaired.

Make sure you do not have vac leaks. I know you might looked, but make absolutely sure.

Run a sweep test on the TPS to make sure the voltage feed back to ECU does not skip or skip when rolling into the throttle.

Make sure the valves are in spec

Spark plugs

Sync throttle bodies, then rev up to about 2500 rpm, do they stay in sync or go out?

Check gear position sensor resistance in all gears

Make sure you have proper fuel pressure

Check spark plug end cap resistances with units cold and hot and make they are good shape. Snip wires back a few mm and then thread back into wire to assure proper connection.

If you have a PowerCommander on it, make sure the TPS is calibrated correctly in the software.

Make sure you have sorted out mapping at idle and just above idle.

If not cured, you then consider a leak down test to assure you don’t have a weak cylinder and you compensated idle sync for a mechanical issue.

There are more things I am forgetting, but these can definitely all cause issues as you describe.

-ms
 
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