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Discussion Starter #1
Hi All,


I have a 2004 CBR600F4i and I am pretty unhappy with the mpg figures. All I can get is around 90-100 miles until the reserve light comes on.
After replacing this week, there is absolutely no difference to the consumption.
I decided to check the exhaust and held my hand close to the exit of the exhaust pipe and noticed unburnt petrol is spraying out of the exhaust pipe, especially if I open the throttle! :icon_emm:

So before you say spark plugs, I must say bike is at 34000 miles and plugs were changed at 28000. Oil changed recently about 1000 miles ago, I checked map sensor and vacuum hose, seemed to be correctly connected, checked air filter( was clean), checked the sensor on top of the airbox( disconnected and ECU gave a fault light so must be working right)...

I am not sure what else might be causing this but I am running out of ideas, and smell of unburnt petrol is noticeable when I first start the bike.

Performance-wise, there are no symptoms, it runs fine, idles normal, does not stall or knock, just consumes hell of a lot petrol.

People seem to be getting 150 miles per tank and me getting only 90 is just annoying, especially if I cannot pinpoint what might be the issue.

About the bike, it has a full Delkevic exhaust pipe on it, but it already had it when I bought it and did not have such poor mileage at that time. Other than that, only different part is K&N air filter but I do not think that is the issue.

If you could help me, I would be very grateful as I am stuck at the moment and do not want to take it to a garage since they dont seem to have a clue either.
 

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How do you know it's not the fpr?
You didn't mention anything about it except in your title. Did you do the test: remove fpr's vacuum line and turn the key on? (Assuming you have an external fpr in your F4i ??)
With 6000 miles on your plugs, I'd want to see what they look like. Wet?
I hope your not getting fuel in your oil...

At first description, it does sound like a failing fpr.
 

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Discussion Starter #3
How do you know it's not the fpr?
You didn't mention anything about it except in your title. Did you do the test: remove fpr's vacuum line and turn the key on? (Assuming you have an external fpr in your F4i ??)
With 6000 miles on your plugs, I'd want to see what they look like. Wet?
I hope your not getting fuel in your oil...

At first description, it does sound like a failing fpr.
Sorry didnt mean to be rude its just english is not my mother tongue :)
I replaced the fpr removed the black plugs it came with :)
Do you think it might be spark plugs, Would they effect mpg im getting?
 

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I guess I was a little direct, but honestly, no malice intended. I didn't see anything rude at all in your post. :)

I'm not nearly as knowledgeable as some here, so I can only guess a couple things with your information.

Assuming you replaced with the proper plugs, I don't see that as the problem, but I don't really know.
Perhaps a faulty new fpr, or a fuel line leaking.
Did you replace crush washers and torque properly when you hooked up the fuel line banjo fittings?
Fuel return line in proper shape?
Vacuum line from fpr to throttle bodies?
Any leaks or puddles?
I've heard of gas leaking thru a faulty vent or overflow tube inside the tank...

That's about all I got... :idunno:
 

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Discussion Starter #5
Someone told me faulty spark plugs, might cause the low mpg.
The reasoning was if they are sparking late or incorrectly, the excess fuel might be getting dumped through the exhaust pipe.
Naturally, I asked wouldnt that decrease the performance, and I wouldnt get low mileage because after all it is the same fuel in the chamber, but he said ECU might be trying to compensate for low quality burning of fuel by dumping more fuel in the cylinders.

Do you think spark plugs might have anything to do with this? My theory( far fetched maybe) is that bike was running too lean in the beginning due to K&N air filter and open exhaust, got too hot, spark plug heads just degraded over time and now they are misfiring, causing the too rich syndrome..
Am I just running after the wrong diagnosis here ?

Believe me, I am seeing this problem in my dreams and wake up all puzzled, I hate it when I can cant solve something! :)
 

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Throw in a new set if you're that concerned, but as long as you have the proper plugs and they are gapped correctly, the issue is something else.
Are you running a power commander?
 

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Discussion Starter #7
Throw in a new set if you're that concerned, but as long as you have the proper plugs and they are gapped correctly, the issue is something else.
Are you running a power commander?
I agree with you on the plugs, I am not convinced that they are the issue, maybe the end result of running rich, they could be fouled a bit but not the root cause.

I am not running a power commander, it is a very basic setup, just an aftermarket stainless steel exhaust from previous owner and a K&N filter.

Do you think it might have something to do with MAP sensor, or IAT sensor? I removed them both to see if ECU will pick that up and it gave error messages for both seperately so I assumed they are allright?:hmm:
 

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Hi All,


I have a 2004 CBR600F4i and I am pretty unhappy with the mpg figures. All I can get is around 90-100 miles until the reserve light comes on.
After replacing this week, there is absolutely no difference to the consumption.
I decided to check the exhaust and held my hand close to the exit of the exhaust pipe and noticed unburnt petrol is spraying out of the exhaust pipe, especially if I open the throttle! :icon_emm:
Are you sure it's petrol and not just water (which is entirely normal when the exhaust is cool)? If it was running rich enough to be spraying unburnt fuel out I would also be expecting to see clouds of black smoke as well, and it would be fouling plugs and running like a pig if it was that rich.

With a cold engine the exhaust will smell of fuel a bit since the ECU richens the mixture. If it smells of fuel all the time, then you may have a bad engine temperature sensor.
 
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