Back firing and im not talking about the beans I had for lunch - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 20 (permalink) Old 02-12-2007, 04:09 PM Thread Starter
 
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Back firing and im not talking about the beans I had for lunch

Im having a little issue with backfiring when I decelerate. its not huriting my bike just its loud and I want he bike to pass CA smog when its due.

I know ther is something on the deceleration pump on the engine but i cant find the info.

Any help?

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post #2 of 20 (permalink) Old 02-12-2007, 04:34 PM
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Is it backfiring or is it just the normal popping you get with this bike. A backfire on the 750 is very loud. The popping is annoying but won't hurt anything and is normal. The popping is caused by the anti smog crap Kaw put on the bike.

VN750 goes vrooom vroom pop pop pop.

Jim W
93 VN 750 "Ursula"
Moved R/R 08Sep06
R/R rewire 17Feb07
New R/R, Installed 14Jun08
New Stator installed 10 Jun08
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21480 Miles
VROC #8542
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post #3 of 20 (permalink) Old 02-12-2007, 05:29 PM
 
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The popping may be caused by an exhaust leak. When you first start the bike feel the exhaust for leaks before it gets hot. Adjusting the fuel mixture might also help the popping.
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post #4 of 20 (permalink) Old 02-13-2007, 10:48 AM
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Mine did that before I marbled. If you marble, you'll quiet down the popping to a soft rumble, but if you are worried about passing the emissions test it might fail you. I assume you have to get your bike inspected every year? Can you have an emissions test done to see whether your bike will pass? If so, I'd marble the bike and then fill up with gas, add about 1/4 oz of acetone to the tank and then go get it tested. I'm pretty sure you'd pass. If it passes, then you know what to do when it's time for inspection. (of course the right thing to do would be to run a dab of acetone in the gas all the time)

The acetone will cause your fuel to burn more effeciently and completely and have less waste through the exhaust, and less noxious emissions.

Fergy
Kyle, TX VN750.com member #707 VROC#19556
2002 VN1500 Classic
Spline Lube Procedure, with photos, R/R Relocation and Coil Mod
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post #5 of 20 (permalink) Old 02-13-2007, 12:06 PM
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Hmm,not sure my replie went through. I had the same backfire with mine until I marbled.And it to was a loud backfire not what I would call popping.

Steve from Pittsburgh
2005 vn750
modified knifemaker driver boards
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post #6 of 20 (permalink) Old 02-13-2007, 12:08 PM
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I agree, it was an explosion on occasion. Now it just rumbles when I decel.

Fergy
Kyle, TX VN750.com member #707 VROC#19556
2002 VN1500 Classic
Spline Lube Procedure, with photos, R/R Relocation and Coil Mod
Rusty Tank Cleaning!
Electrical Fault Finding Flowchart
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post #7 of 20 (permalink) Old 02-13-2007, 02:39 PM
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CA emissions are tougher than the rest of the country, so whatever you do to fix the problem (outside of an exhaust leak), make sure you can un-do in time for the inspection.

The air/fuel adjustment screw on both cylinders is factory set at 1 5/8ths turns out - most folks find that way too lean, and that's what creates the popping on decel. If your bike is new or no one's ever messed around with the setting, the screws will be behind small bits of lead - holler if you can't find 'em, and the Forum folks can walk you through getting the lead out (ha ha). The screws can be turned back to the factory setting before you go for inspection.

If that doesn't work, then try "coastering" or "marbling", as folks are suggesting. The easiest way to do this is to stick a marble in the hoses leading to the reed valves on each side of the engine block. This cuts off the air flow that Kaw introduces into the engine to burn unburned fuel in the exhaust (thus creating the popping) - it's to reduce emissions. Again, the marbles can be removed before your emissions inspection, if that turns out to help the problem.

The backfiring - kaboom! versus "pop pop pop" - is probably due to a leak in the exhaust, so check that first and tighten up all fasteners (your torques can be found in the Clymer's manual and I think there's a list in the Verses). Any idea which side the backfiring is coming from?

Good luck!

C
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post #8 of 20 (permalink) Old 02-13-2007, 06:14 PM
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Carb Adjustment

Adjusting the carb screws is one more thing on my list of "to dos" this spring. I was wondering if anyone who adjusted the carb screws has seen any difference in performance of the bike when the fuel is richened up; in either a decrease in gas mileage or increase in performance. And, if I can connect two threads, I wonder if the increased spark from iridium plugs can make a richened bike run a bit stronger?? Hmmmmm.......

Something to think about......

Ben-
SW Ohio

'02 VN750
Pipes drilled
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R/R relocated
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Lovin Life.
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post #9 of 20 (permalink) Old 02-13-2007, 06:21 PM
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The carb screws will adjust idle mix, so it will not have any affect on the performance of the bike under throttle, only on decel. Which, when added to the iridium plugs, might make the bike idle smoother, but again won't have any affect on throttle performance since those screws only adjust idle mix. Iridium plugs will generally make the bike a little more responsive, but whether you'll feel it or not is a good question.

Your main jets have most affect on above idle performance. Hope this helps!

Fergy
Kyle, TX VN750.com member #707 VROC#19556
2002 VN1500 Classic
Spline Lube Procedure, with photos, R/R Relocation and Coil Mod
Rusty Tank Cleaning!
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post #10 of 20 (permalink) Old 02-14-2007, 09:55 AM Thread Starter
 
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Wow

Ok, I guess back firing is a to strong of a word. I have heard the BANG when trying to cold start when I left the bike outside over night (cold blooded B***H).

So the POP POP on decel is normal.

I have orderd the iridium plugs and they will be here today (crossing fingers).

And as for the Acetone? I have been told that i should run regular fuel now you are telling me to add an additive to increase clean burning.

So with Iridium plugs and Supreme gas i should hear less popping?

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