Poor fuel consumption :-( help !!

I have a 2003 vfr800 vtec and Im only getting 115 miles from a full tank of fuel before it hits reserve ! I have read they can easily manage between 140-180 miles from a full tank. Does anyone have any idea whats going on with my bike ?

 

Thats real bad, when was the last time you cleaned or changed your air filter? If the bike been sitting awhile, critters like to nest up in there.Try running injector cleaner like sea foam ect. Unless your ridding above 6k all the time. I get roughly 200 to a tank commuting, as long as I dont get up into the vtec range. Sumthin aint right brotha

 

Well I haven't owned the bike long myself but the guy that i got it off didn't use it very much . Thanks for your tips though mate I will try them all.

 

At what rpm does the vfr become as fuel efficient as it possibly can be ?

 

Why not inspect your plugs for any deviation from the standard color, a toasty light brown ??




Always possible one plug isn't firing. :sleeping: Could be a bad sensor or thermostat if it never reaches proper temperature, 180-190F.

 

Checking air filter and plugs a good idea.

What temp is the bike running at? If your thermostat is stuck open, the ECU will keep it running rich resulting in poor mileage. Most of our t-stats open at 170, and these bikes run hot. Even in temps below 50*, you should easily be running at 170+.

 

Well after a 25 minute commute to work at speeds averaging around 85mph the bike's temperature was only around 62-65 degrees celsius.

Thanks for all the helpful tips so far guys keep them coming

 

We've probably solved the problem. Your tstat is stuck open, your running to cool. Way too cool. Change t-stat. Flush & fill system. Burp it accordingly. Watch your gas mileage increase significantly. Done.

 

Sorry for the extra questions but Im not mechanically minded. How do I flush and fill the system and what do you mean by "burp" it accordingly ?

 

I appreciate the insight. I have been getting around 35 MPG on my 2002. I thought it was just me. I've noticed that it only gets above 155-160 f while parked at stop lights. I'm going to replace the thermostat and see what happens. I'm thinking that i should be getting 40 MPG.

 

OH.. is there a FAQ on how to replace thermostat?

 

Sorry guys, but I'm not qualified to answer how to change the T-stat on the 6th gens. I'm sure there is some sort of a thread on here. Maybe try using the "advanced search" button towards the upper right of this page?

Or someone else can chimp in.

 

There are manuals here available for download. contains everything you need to know

 

I did mine on my 2004 recently it isn't really too hard just looks that way

First make sure tank is fairly empty and bike is cold

then undo front tank bolts and raise tank remove airbox and assorted plumbing attached to airbox

remove both side fairings and radiator cap then drain coolant into a catch pan (bolt on water pump on left side of bike ) get ready to jump out of the way as it squirts quite a way

then the throttle bodies need to be removed and you will need a loong + head screwdriver to put through holes in the frame to loosen the insulator clamp (rubber intake boots )

also remove the idle adjuster from it's holder by the oil filler capand the throttle cables from the left of the throttle bodies

then I used a piece of tape on the rear valve cover and placed a thin piece of wood between this and the throttle bodies and levered the assembly free from the insulators ( this makes a sound like something just broke)

then carefully work the idle adjuster free from the valley (it can be broken reasonably easily )and have a small table on the right hand side of the bike and in doing this you can leave all the fuel hoses attached and gently work the throttle bodies out and sit them on the table next to the bike ( don't be too rough or you may break something )


the thermostat housing is in the middle of the "V" undo the hose clamps on all 4 main hoses and remove the clamp on the small hoses and work the housing free from the hoses (top middle of photo)



undo 2x bolts and take top of t-stat housing and replace t-stat along with the o-ring in the housing lid

then put it all back together whilst calling HONDA all sorts of amusing names and keep a swear jar handy ( or beer )
A small wipe of oil ( or personal lube ) on the inside of the insulators will make refitting the throttle bodies a lot easier

When doing up the insulator clamps leave about 7mm between the internal faces the screw goes through or you will distort the insulator and possibly introduce an air leak

flush the system with de-mineralised water not tap water

then I used honda blue 50/50 pre-mix (silicate free)car coolant to fill the system run the bike on side stand with the rad cap off reving the bike to purge the air from the system and then replace the rad cap as the air stops bubbling up topping up first

make sure to clean and refill the overflow bottle with clean coolant

run bike up to temp and allow to cool right down then check coolant in radiator and top up if needed also check overflow tank

put fairing back on go for a ride bike should be over 65° C within a mile or so and off the cold idle circuit

you do this at your own risk and I take no responsibility for you stuffing it up

I bought new insulators and 2 x short hoses when I did it in case they split , they don't cost a lot and you will need to order the t-stat anyway

Have fun and allow twice the amount of time you think it will take , it took me 3 hours but I think I could knock it out in 2 hrs if I was to do it again

 

I love this forum! thanks grumpy for the in depth directions

 

Good writeup. Thanks

 

Just to update. I replaced thermostat. engine now warms up very fast. Have not checked mileage yet. Grumpys write up helped. It took me 6 hours the first time. I pulled throttle bodies off 3 times. Once to replace thermostat, once to replace hose that was leaking (dont know if i caused it or it was just old) and once because i failed to seat the throttle bodies properly. I got it down to half an hour. practice makes perfect! What I learned: allow twice as much time, have replacement o ring and have replacement hose available just in case.

 

Nice progress, Leaky. I was the same way when I go my bike. Think the first oil change took me over an hour because I didn't want to break anything, didn't know how to line the fairings back up, etc. After that, it became about a 15 minute process.

 

Did making those changes help any bit or are you still getting low mpg?

My guess would be bad airflow causing a rich mixture but that in turn would lead to bad performance I would think? Check hoses and everything are tightened properly, any evidence of petrol in exhaust? Is it backfiring?

 

I was at 37 MPG on my first tank after thermostat replacement. I guess that's normal given spirited suburban driving. Lots of stop/go up shift/downshift.