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Discussion Starter · #1 ·
Its an 03 with 12k miles
Dual holeshot high mounts
TRE
power commander
I have the idle set at about 1300 rpm.

The PO stated that the PCIII had a custom tune - Due to the flat spots at 3k and 8k, i call his bluff.

Once in a while on throttle blips, i get an airbox backfire. I read all bout it on here, and i have done the pair disconnect. After the pair mod, there was a signifigant reduction in exhaust backfire, but the airbox backfire is still there. It only occurs at the slightest throttle blip when the bike is warmed up. While coming up to a turn this morning, i down shifted from 3rd to 2nd, I blipped the throttle before dropping the clutch and it backfired and stalled. I would assume that its a little lean down low, and a new tune will clean up the powerband, but im thinking that the backfire may be a sign of a valve adjustment in the near future. Any input?
 

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It's Ironic I was just about to post about "airbox backfire"-

Mines a 05 SVS - Yoshi RS3 slipon + desnorkle- no ECU mods, even the PAIR has been left alone.

But this morning (bikes cool, 70 degrees or so) I blipped the throttle as I turned it on and it HATED it (well sounded like that...) Airbox backfire sounds really bad... - blipping the throttle when its "cool" seems to do it consistently

What causes this?

- Sorry for the thread jacking- just figured id post it since its semi-relevant, at least you know it may not be the PC...

Seems strange yours does it when warmed up though.

Could this be a spark issue?

EDIT: I am on a SV650 - sorry was just clicking on latest posts haha didn't realize it was a 1000 thread- suppose it could easily be similar though.
 

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Sounds like a lean condition, since you are backfiring from both ends.

His "custom tune" could be BS, or custom crap from someone who does not know what they are doing. Ask him for the Dyno runs, with A/F analyzer, graphs. That is the only proper way to make a good custom map.

My advice would be take off all the PC stuff, leave on the cans, and run a stock air filter. That is basically how I have my 03 set up and it runs like a top. Plenty of power.
 

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Would suggest you (both) check the TPS adjustment as late enrichment will cause the 'sneezing' back into the airbox. Even with it set properly, the big twins tend to NOT like sudden throttle movements from idle speeds and the occasional small intake fart seems like it's par for the course.
 

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***UPDATE***

I haven't gotten to the throttle body sync or the TPS adjustment yet, but i switched from 91 to 97 octane gas and the problem has gone away.
Ah good!:) Seeing your fuel octane #'s has me wondering where you are located? We have 87,89,93 around here in PA. Is the 97 you found pump gas with R+M/2 rating? Sounds like you might be out of the USA?

AND......wanted to mention that valve adjustment can have an impact on airbox popping if they are on the tight side. Mine popped all the time after gassing up, but mostly doesn't now that I've loosened the valves to the wide side of the specs.
 
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