Still having some fuel issues...

I've been fighting with a little fuel issue since I got this bike (2002, non abs).

When I first got the bike it was getting about 23 mpg. I replaced the thermostat and I now get 29 mpg give or take a few. Reading some of the MPG posts I feel like I'm still not getting what I should be. I've read that some people still get over 30mpg while riding hard. I have to baby it to get my 29.

Anyway here's waht I know and have done so far...

1. Replaced thermostat
2. Flapper valve mod
3. O2 sensor resistor mod (will likely leave reverse this one to stock permanly, no change in mpg with this mod.)
4. Pair valve block.

That's the only mods on this bike. When I start the bike it's very strong gas smelling exaust, and when I get to work (engine up to temp) the exhaust still has a very very heavy gas smell so I'm pretty sure it's still running very rich.

The milage seems to stay the same regardless of if I reverse the mods (# 2, 3, and 4 above).


Anyo other thoughts of what would make an 02 run very rich?

Any suggestions woudl be greatly appreciated.

Also, I have not yet chagned the sparkplugs. Could the plugs have any cause for this?

The bike runs great, doesn't miss, or sputter and does everything I ask if it and wants more.

Chip

 

Have you shorted the system check connector and checked the codes thrown (if any) sometimes codes will be stored yet not trigger the FI light. Might give some sort of hint as to what is going wrong. Flapper, PAIR, and O2 sensor mod make a negligible change in MPG. I recently did this with mine, as well as a full exhaust, and only lost about 2mpg so I'm down to 39-40. Something has got to be going on here that we haven't figured out yet.

Bad fuel pressure regulator? Its just a guess but there is a test for it in the service manual.

 

I'll check the PDF service manual i have on the PC here....

Is there a procedure for shorting to check for codes? I'll also check for the procuedure for the pressure regulator.

The main reason I put the resistor/o2 sensor mod was to rule out a bad o2 sensor or two... Being that the milsage hasn't changes I'll likely plug them back in and be done with it.

 

Where's the connector located to short to check the blink codes on the FI light? I found on a 5th gen where it's located under the seat. Is the 6th gen in the the same area? I saw no reference to a connector to short in the shop manual.

 

UGH... I found it, under the upper cowl. Does the cowl have to be removed or is there a way to get to it w/out removing it.

 

Make sure the fuel return line between the tank and the pressure reg isn't kinked...that'll very much increase fuel presssure. Otherwise I like Meatloaf's pressure regulator idea.

 

The front cowl does not have to come off but the right meter panel does. Its the painted piece between the dash and the front cowl. You should be able to reach in there enough to plug in a jumper wire. The procedure is in the manual. Chapter 5 I believe. This is also where the procedure is for checking everything with the fuel system including the fuel pressure regulator.

I think you will also need a MityVac or similar for testing the FPR, commonly used for bleeding brake likes and available at harbor freight for cheap and most auto parts stores.

Injector issues have also crossed my mind but I just don't see the bike running so well with that. If all else fails you might be able to take it to a dealer and just have them run a diagnostics on it. Do you know when the last time the plugs were changed? You might as well check at least the front two while you are doing all this to at least see how they are. If you remove the tank to check the FPR, might as well check the back two as well.

Using that much fuel has me concerned about cylinder walls being washed down and contaminating the oil. How does your oil look/smell after a change? When I had my t-stat go out I put 800 miles on fresh oil and in that time I had over a pint more oil come out than I put in which smelled of gas strongly.

Are you running the stock exhaust? Stock sprockets? No Power Commander? A few changes that each drop MPG add up but you still seem low. Are your operating temps in the normal range after changing the t-stat? (168F minimum) I ask because there have been a few around that have replaced a bad t-stat only to find out the new t-stat was faulty.

As my thoughts run through I would also suggest testing the MAP and IAT sensors. IIRC, I sent at least an IAT sensor (or maybe one of each) to Elwray via pay it forward at the cost of shipping. He didn't need them as his were fine and said he would do the same for the next one in need... If they don't test well you might hit him up to save some money or try something as a test. The IAT is cheap but the MAP isn't.

Sorry for the late night rambling but this is driving me crazy. Something just isn't quite right here and it just shouldn't be this darn difficult.

 

There isn't much a dealer can do that you can't by reading the diagnostic memory. Except maybe have the equipment to run a fuel pressure test...which wouldn't be a bad idea. Are you sure the vacuum line to pressure regulator is intact, and not kinked?