Please help. Ridiculous gas mileage

What in the world can cause a stock 2002 VFR800 with only 13K on the clock to get 120 miles to a full tank. And this is taking it easy on a highway

- clean air filter
- stock gearing
- Unplugged emissions stuff (did't make a difference)
- About to disable 02 censor

Also when I have brights on battery gets drained within 20 minutes and bike starts to cut off when I pull in the clutch.

This is my daily transport to work, and it's killing me. Anyone near ATL can help me swap parts to trouble shoot? Any ideas how to fix this?

Please

 

dont disable 02 if you dont have a PC on it.
sounds electrical due to HB issue.
also remove the emmisions stuff as well as the pair valve < it might be stuck open. You will get better throttle response w/o all that junk.
but you need to figure out the electrical issue first

 

Electrical is probably rectifier going bad, but that doesn't worry me that bad. Gas mileage is whats killing me. Trying to save up for a race bike and need to save every penny

 

How's the temperature? Running cool? Maybe a stuck t-stat causing it to run rich?

 

Temp is good. 160 on cool days, 210 in heavy traffic when 100 degrees out, before fans come on

 

"Also when I have brights on battery gets drained within 20 minutes and bike starts to cut off when I pull in the clutch."

this will affect ECU and all sensors as well.
If for any reason it is not getting full voltage it will mess up the systems.

 

Would I get a FI light if electrical system is affected by a low voltage?

 

it would seem to be intermittent so possably not.
you could unplug air temp sensor and see if that throws a code and if it affects how the bike runs

 

Air temp reading on the dash seems to be accurate. O2 censor going wack?

 

Ding ding ding ding. We have a winner. Temperature should never drop below 168F even when below freezing. Your thermostat is stuck in the open position. This causes the engine to run "cold" as far as the ECU is concerned. In order for emissions to be at their best, engine temperature needs to be at a certain point. The ECU tries to correct this and increases fuel consumption in order to get it warmed up.

This is the EXACT same thing that happened when my thermostat stuck open. MPG slowly started dropping and ended up almost exactly where you are now. Check your oil. Is it higher than normal? When I had this happen I had gas getting by the rings as well and noticed an increased oil level. I changed the oil and it was clearly thinned out and smelled of gas too.

 

I will check the temps closely next time I ride. 160 was a guess. pretty sure it was that when I looked last.

 

I think that you can test this by checking the temps at the radiators as well. IIRC, when the thermostat is closed, only the right radiator will get warm/hot until the thermostat opens. If the thermostat is stuck open, the coolant is flows to both radiators as soon as the engine starts running and they will warm up at relatively the same rate. Hopefully someone can chime in and confirm this.

If it is a stuck t-stat... it is a time consuming thing to replace. It isn't really all that difficult, but it sure is a royal pain in the ass to get to the thermostat housing as you have to remove the airbox and throttle body assembly just to get to it.

 

I agree with mr meat, weather he is right or not (heck if i know, i hate electrical problems) sensors rely on electricity, and if you are that low on juce none of the sensors are going to operate correctly, thus none of your engine is going to run correctly. first step is to get the electrical working.

not to mention that if your juce is off you run a slight risk in burning up a few sensors or electronic components and then your next question will be why wont my bike run at all.

but heck if i know, i didnt even lube my chain correctly the other day.

 

Also if your dumping that much fuel into the cylinders, it's washing them down. Err washing the oil off and the friction is not doing the rings and walls any good. Left long enough you will get accelerated wear and loose the cross hatch in them. That's what keeps some oil on the wall for lubrication.

 

So, both rads heat up at the same time from cold. Temp barely reached 160 today. It was 70 degrees out air temp. So we agree it must be thermostat and running wrong map?

 

Yup, order a new one, get some antifreeze, and pick up a case of beer and a long phillips screwdriver. There are a few tutorials around here on the site on the manual also describes the procedure quite well. Everything else needed are just standard tools. You'll probably also want 2 new sealing washers for the coolant system as you have to drain the system in 2 places. Its a good time to flush the coolant anyways

 

:thumbsup:Well done gentlemen

 

Anyone has a used one laying around collecting dust? I m saving every penny for a new track bike ))

 

My guess is a used T-stat is going to do just what yours is doing.

You're going to have to splurge for a new one.

 

Its a $25-$30 part. Splurge for new.