2007 M109R decel popping and backfire after Cobra FI2000R
I need to find out why I have a trailing deceleration popping and backfire issue after installing the power pro. I have Hardchrome sideburners that are straight exhaust. Stock air filters. The bike accelerates great and runs like a champ!
I called Cobra Engineering and they don't have any idea why it is doing it.
Anyone have any suggestions as to why this is happening?
Thanks in advance
Have you checked to see if you have exhaust header leak, you might be sucking air under deaceleration.Originally Posted by My1st109
C-One
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fuel
hate saying it. What you running for fuel?? may want to try a little lower octane. If you cant find any other issue.
Your thread title and thread content are a little misleading.....in the title you refer to it as an FI2000R...in the thread you call it a PowerPro...two different units. Which one do you have? If it's a 2000R you probably have one of the pots set too lean, if it's a PowerPro, I have no idead whats causing this problem....
grampi, sorry for the confusion. It is an FI2000R. Exhaust is all tight. I check it with a soapy water solution. I have the settings set from the factory. I too was thinking that I need to fine tune the green pot. Will try tomorrow and see what I can figure out.
Thanks
You need to adjust your Fi2000r unit. Take the cover off and turn the first adjuster up 1/2 point, in other words if it is set to "2" set it to "2.5" and run the bike to see if that worked, you may have to do it a few times and may even have to adjust #2 adjuster up a little also.
If you haven't blocked the PAIR valves, do that. It's either that or an exhaust leak. Not that you're adding more fuel some of it makes it into the exhaust. Add a little air in and you get a pop.
Life has no remote control, get up and change it yourself.
Well, I hope I have this right. If not, anyone’s welcome to correct me.
Consider that when a motorcycle is being driven at high rpm’s, that the cylinders are receiving gobs of fuel and air, at a so-called ‘ideal’ mixture ratio of 14.7:1 (14.7 parts air to 1 part fuel). Perfect for combustion inside the cylinders.
Now imagine that you suddenly snap the throttle shut to decelerate.
The result is that the ‘fuel’ part of the equation changes significantly – dropping down to the equivalent of near idle.
Meanwhile, the ‘air’ part of the equation really hasn’t changed much at all. Even as engine compression starts to slow the bike down, the pistons continue to suck in huge volumes of air. The result is an overly ‘lean’ fuel mixture. (too much air, and not enough fuel).
Because the mixture is very lean, it has difficulty combusting inside the cylinders, and it instead gets passed through to the exhaust system.
When it gets into the hot exhaust pipes, some of the mixture accumulates to the point where it can combust, and the result is the popping or backfiring noise during deceleration.
This effect is emphasized when using after-market exhaust systems. That’s because after-market pipes don't suppress the popping noise as effectively as the stock pipes with mufflers.
Motorcycles that don’t have fuel injection have a device built into the carburetor intended to correct deceleration popping, called an ‘air cutoff valve’. This device cuts off, or reduces the amount of air intake during deceleration so that the air / fuel mixture doesn’t become so lean as to cause decel popping.
(above: Air Cutoff Valve)
Motorcycles that have fuel injection (like the M109R) rely on the ‘mapping’ / internal software program of the stock Engine Control Module (ECM), or an after-market fuel controller (such as the Cobra FI2000) to automatically adjust the mixture, and to compensate for deceleration.
Another component on the M109R that can influence the mixture, is the P.A.I.R. Valve (Pulsed Air Intake Reed Valve).
It injects air from the airbox directly into the exhaust ports to ignite (combust) unburned hydrocarbons in the cylinders. Its purpose is one of emissions control: to reduce carbon monoxide emissions out of the tailpipe.
People that have installed after-market exhaust systems have had success in reducing decel popping by disconnecting the P.A.I.R. Valve, and installing small cover plates on the outside of the cylinder jugs.
If your Fuel Controller is not suspect, and the P.A.I.R. valve has been decommissioned, then there could be something else at play, such as an air leak.
But first we have to talk about your garden hose....
When you attach a spray nozzle to to the end of the garden hose, it has to have a small rubber gasket installed inside the hose end. Otherwise, no matter how much you tighten the spray nozzle onto the hose, water still manages to spray out of the sides.
How the exhaust system connects to the engine on your motorcycle is no different.
There’s supposed to be a gasket installed at the end of the header pipe, called an exhaust ‘crush gasket’. It’s a small ring-shaped device that flattens out to form a tight seal, when you tighten the header pipe to the exhaust port.
These crush gaskets are supposed to be replaced every time that the pipes are removed & re-installed. Once they’re compressed, they don’t rebound when remove the pipe. They stay flat.
It’s a common problem that people re-use the crush gaskets, and they no longer form a tight seal – even though the header pipe bolts seem perfectly tightened. And some people leave them out altogether.
This diagram shows installation of the crush gasket (Part item #6):
And here’s what typical exhaust crush gaskets look like:
A header pipe air leak will also result in decel popping.
If you still suspect the FI2000 Fuel Controller settings, then I’d recommend that you return to factory default settings, and then set the ‘Idle’ pot a little richer. Just a thought...
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Last edited by asviewedfrommars; 05-16-2012 at 11:19 PM.
Sounds reasonable but the air is greatly reduced by the butterflies going shut. So it does change.Well, I hope I have this right. If not, anyone’s welcome to correct me.
Consider that when a motorcycle is being driven at high rpm’s, that the cylinders are receiving gobs of fuel and air, at a so-called ‘ideal’ mixture ratio of 14.7:1 (14.7 parts air to 1 part fuel). Perfect for combustion inside the cylinders.
Now imagine that you suddenly snap the throttle shut to decelerate.
The result is that the ‘fuel’ part of the equation changes significantly – dropping down to the equivalent of near idle.
[COLOR=#222222]Meanwhile, the ‘air’ part of the equation really hasn’t changed at all.
.
Removing the secondary butterflies will change the throttle closing rev rate. To try and explain it I need you to use your imagination. With the secondaries installed from factory your bike will sounds like vrooooooooom, vrooooooooom, as you twist the throttle and close it quickly the engine will still tend to hold that rev.
With them removed you get a very quick rev where the bike sounds like vrom, vrom, closing the rev very quickly. Now I'm not exactly sure what the total function the secondaries play but I did notice with them removed I had less popping coming from the pipe on decel!
I am going to try the marble trick on the pair valve hoses and see if that helps. If it does I may just eliminate the marbles and put the pair valve covers in place. I am hoping this will get rid of the popping and backfiring.
I bought brand new exhaust gaskets when I replaced the stock exhaust with the aftermarket sideburners. I checked and re-checked the head bolts for tightness and even did the check for an exhaust leak using a soapy water mix. All is good.
My next move is to take it for a ride tomorrow and try adjusting the FI2000R unit. I installed the marbles today in the pair valve hoses.
I'll report back more tomorrow.
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