Huge backfiring issue

[LikketySplit]

After installing the big 3, I'm having incredible backfiring and bubbling on decel. I rarely downshift because it's so embarrassing. Actually scares ME sometimes it backfires so hard.

Here's the setup:

Thunder Mfg. air intake
Cobra PowerPro Fi2000
V&H Slash Cut slipons.

My understanding is that the Vaquero does not have an O2 sensor, so what is the powerpro actually doing?

Is my first step checking for exhaust leaks?

Any help/advice is greatly appreciated.

[RACNRAY]

First off, the fresh air hose for the Kleen air system should be blocked off if it alreay has not been.

Proper fuel injection tuning goes a long way to eliminate decel popping. Is the cobra unit you have the "self adjusting" unit?

As has been documented the 1700's have the potential for intake system vacuum leaks, installing the Thunder intake gasket can make a world of difference. I will not tune a 1700 UNLESS it has that gasket installed.

RACNRAY

[LikketySplit]

Hi Ray - I have plugged the hose per Thunder's instructions, I'm assuming I got the right one. the hose coming off the back of the front cylinder has the little filter installed. The Cobra unit is the self adjusting "80 times a second" unit, so no mapping or adjustments.
I did purchase and install the intake gasket from Thunder on the back of the throttle body.

[Boscoe]

Check exhaust system for leaks. New crush washers at the headers, tight clean clamps and connections everywhere else. Any air leaking in will cause this issue.

[ringadingh]

^^^ I agree, theres a good chance you have a leak at the exhaust port, once in a while it can take a couple attempts to get it right.

[LikketySplit]

Would the header have been loosened to install slip-ons? The dealer did it for me so I'm not sure what was involved. I'll check V&H's site for installation notes and see what it says.

Thanks for the input, I figured it had to be air getting in somewhere in the exhaust.

[Silent Sam]

Might be blowin in the wind here...but you might check the plug wires for correct placement..if one or both are fireing at bottom stroke..exhaust valve open...

Should be easy to check anyway...

[redjay]

If you only had slip on mufflers put on there should be no leak at the cylinder heads.
I dont know of anyone that makes the head pipes for the 1700's, only slip on mufflers.

[cnc]

Might be blowin in the wind here...but you might check the plug wires for correct placement..if one or both are fireing at bottom stroke..exhaust valve open...

Should be easy to check anyway...

If it is a lost spark system like the 1600 then it would make no difference. The four plugs fire at the same time while one cylinder is on the compression stroke and the other is on the exhaust stroke. If it is not a lost spark system on the 1700 then reversing the leads and the bike would not run at all. There are only 1 plug per cylinder on the 1700.

[Silent Sam]

One wire per cyl on the 1600...yea I knew I was jus makin smoke ! (I have an 02 Nomad)

.."wasted spark"...4 wire/4 spark plugs, Does that mean that both cyls fire at TDC on both strokes...?
No compression on the exhaust stroke thus no "power stroke"...

However wouldnt that mean that if -one wire- from each cyl was hooked to the wrong cyl...(accidently switched), when that wire fired it would spark in the wrong cyl...at "180 degrees-out"..thus sparking at Bottom-DC in that "wrong-cyl" ! ?

I know this is an old question..and I'm sure its explained in detail somewhere on the forum.. I should go out to the garage and work on my bike instead of sittin here complicating the universe !

[cnc]

One wire per cyl on the 1600...yea I knew I was jus makin smoke ! (I have an 02 Nomad)

.."wasted spark"...4 wire/4 spark plugs, Does that mean that both cyls fire at TDC on both strokes...?
No compression on the exhaust stroke thus no "power stroke"...

However wouldnt that mean that if -one wire- from each cyl was hooked to the wrong cyl...(accidently switched), when that wire fired it would spark in the wrong cyl...at "180 degrees-out"..thus sparking at Bottom-DC in that "wrong-cyl" ! ?

I know this is an old question..and I'm sure its explained in detail somewhere on the forum.. I should go out to the garage and work on my bike instead of sittin here complicating the universe !

Sam in Wasted spark, two or one plug per cylinder does not matter. In a 2 cylinder motor all plugs fire at the same time with this system, so when one cylinder is on the compression stroke the other is on the exhaust when the plugs fire and visa versa. Switch the leads around and they will still fire at the same time

[RACNRAY]

If the gaskets between the slip-ons and the header were/are in good shape and their are no leaks, that can be eliminated. If the kleen air system is plugged up then the next step is to install the thunder intake gasket between the throttle body and intake manifold. If ur skoot has vacuum leaks they can cause popping now that you no longer have stock mufflers.

THEN...if that does not work then the fuel injection tuner is not delivering the appropriate a/f mixture. I believe cobra put in an adjustable pot to help in the decel popping, check to see if ur unit has that adjustment or call cobra.

You are welcome to call my shop I can talk faster than typing 954-455-9665 florida.

RACNRAY

[LikketySplit]

If the gaskets between the slip-ons and the header were/are in good shape and their are no leaks, that can be eliminated. If the kleen air system is plugged up then the next step is to install the thunder intake gasket between the throttle body and intake manifold. If ur skoot has vacuum leaks they can cause popping now that you no longer have stock mufflers.

THEN...if that does not work then the fuel injection tuner is not delivering the appropriate a/f mixture. I believe cobra put in an adjustable pot to help in the decel popping, check to see if ur unit has that adjustment or call cobra.

You are welcome to call my shop I can talk faster than typing 954-455-9665 florida.


RACNRAY


Thanks Ray - your posts are always interesting and informative, and that's a generous offer. I do have the hose plugged, and a Thunder gasket installed, so now I'm going to check for exhaust leaks and see what I can find.

[hlknvlcn60]

Okay now that we are on tis subject, I too have the Cobra FI2000R auto tuner, V&H 2-1 pro pipe which I know is sealed front to back tightly with new compression gaskets, torqued 3 times since install, so where is this fresh air hose? Is it connected to the TBI on the intake side? I see another nipple in there right next to another one side by side, the other one with that upward rising hose with a black plug on it already. I tried plugging off the hose going upward to an electronic component, started the bike and it ran very low idle and got super rich. I re-hooked it imediatly. My suspicion is the evaporative emissions system like it was on my Meanstreak, I blocked the reeds off on that one, and plugged the recirculating nipple on the TBI, back firing gone forever. It is annnoying sometimes on down shifting when riding the 1700 and getting a fart pop or three on back-off, but most of the time it decels pretty clean. Next week a full open air intake conversion is taking place...a nice one I bought from Roaring Toyz inc. in Sarasota Fla. Like mentioned in another thread already, I will report back after installation and performance. Any other tips from some of you senior guys will be fully appreciated and duly noted.

[AZ Voyager]

Likketysplit.....Just a shot in the dark but I think the hose that you pluged is the cylinder breather, the fresh air hose that needs to be plugged should go up under the tank and dissapear into the darkness, as you look at the right side bowl it should be in the upper left corner about 11 o'clock.

I have plugged the hose per Thunder's instructions, I'm assuming I got the right one. the hose coming off the back of the front cylinder has the little filter installed.

[RACNRAY]

Okay now that we are on tis subject, I too have the Cobra FI2000R auto tuner, V&H 2-1 pro pipe which I know is sealed front to back tightly with new compression gaskets, torqued 3 times since install, so where is this fresh air hose? Is it connected to the TBI on the intake side? I see another nipple in there right next to another one side by side, the other one with that upward rising hose with a black plug on it already. I tried plugging off the hose going upward to an electronic component, started the bike and it ran very low idle and got super rich. I re-hooked it imediatly. My suspicion is the evaporative emissions system like it was on my Meanstreak, I blocked the reeds off on that one, and plugged the recirculating nipple on the TBI, back firing gone forever. It is annnoying sometimes on down shifting when riding the 1700 and getting a fart pop or three on back-off, but most of the time it decels pretty clean. Next week a full open air intake conversion is taking place...a nice one I bought from Roaring Toyz inc. in Sarasota Fla. Like mentioned in another thread already, I will report back after installation and performance. Any other tips from some of you senior guys will be fully appreciated and duly noted.

Don't mess with any of the hoses attached to vacuum nipples on the throttle body. The hose you disconnected with an "electronic component" at the end was the map sensor. Ain't gonna run right with that disconnected.

RACNRAY

[LikketySplit]

Likketysplit.....Just a shot in the dark but I think the hose that you pluged is the cylinder breather, the fresh air hose that needs to be plugged should go up under the tank and dissapear into the darkness, as you look at the right side bowl it should be in the upper left corner about 11 o'clock.

Thanks - I'll check the hose I've plugged off and make sure it's the right one.

[LikketySplit]

So here's an interesting update. Took the bike in for it's first service, and for them to check out the bubbling backfiring. Now remember, I have never once ridden this bike since I picked it up without experiencing heavy bubbling, popping, and serious backfires. So the dealer tells me several things that I'll summarize below, but basically my setup won't work, Cobra unit is mickey mouse, etc., so there is nothing they can do about the backfiring. So I got on the bike, headed for home (about 40 minute mixed ride), and wonder of wonders I didn't get any backfiring. Every time I came to a stop or slowdown, I geared down very heavily, and couldn't make the thing backfire. Still some bubbling, but much less. It popped twice in total, no matter how hard I decelled the engine, any gear. Go figure?

Dealer's comments:

1. Air temp sensor will not read correctly because it is now exposed to ambient air as opposed to the air in the stock air tunnel, which is supposedly much cooler due to the velocity it moves at.
2. Cobra unit only adjust F/A ratio, none of the other factors that other mappers affect.
3. Cobra unit might read 80 times per second, but doesn't adjust anything quick enough to keep up with what is happening with the engine when you decel, accel, etc.

Does any of this make sense?

[Gypsy Dragon]

Dealer's comments:

1. Air temp sensor will not read correctly because it is now exposed to ambient air as opposed to the air in the stock air tunnel, which is supposedly much cooler due to the velocity it moves at.
?

I moved my air temp sensor away from the motor, too. It makes sense that ambient air temp will make for a better A/F mixture. I've never heard someone say the velocity of the air affects the temperature of it, all you have to do to not believe that is ride down the highway in central Texas in the heat of summer...it's like a blast furnace, but I admit that I don't know everything. Maybe one of our professional mechanics will chime in with their opinion soon.

[redjay]

I have the Cobra Powrpro and have never had any backfiring, ever. Chucksters air intake and stock 2010 mufflers.