High Mileage '99 Vfr800 And Poor Fuel Economy.

Hi all!

I've owned a 1999 VFR800 FiX for about half a year now, and been reading the forums for quite a bit now before finally getting down to registering. I'd like, first of all, to offer my thanks to every one on the forums, as the collective contributed information on here has helped me a whole LOT with working on my bike!

She was none the worse for wear when i took over and had to have a lot of tired and worn parts replaced. She is bone stock, has 190,500km on the clock now and running strong! Where i live, it is summer all year round, and it is not uncommon for us to clock up 100,000km on our vehicles in little more than 3 years.

The Viffer is a great bike and i'm enjoying every minute on it. Right now, the only thing bugging me is the fuel consumption. i am only averaging 15km/litre, or about 32 mpg during everyday riding. I have tested the fuel consumption in all conditions i could think of: solo, 2-up, rear pannier fitted and off, easy expressway riding (4-5k rpm) and hard, near-full throttle acceleration. I generally tried to ride the same way as much as i could during each test, changing the conditions only after filling up and performing the calculations. The strange thing is, the consumption did not vary much, it was always between 15-15.5km/litre.

My question is, what else needs to be checked/serviced in order to be achieve mileages closer to what ive seen? (40+ mpg) I do a lot of touring in rural areas where fuel stations can be scarce and would want the peace of mind of a longer tank range....

I have had fresh oil, plugs, new air filter, brakes rebled and tyre pressures checked regularly before testing. The bike can be pushed by hand almost effortlessly, so brake drag is not a factor. Running temps are usually between 95-100deg C.

I noticed however that there is a smell of fresh fuel when the bike gets fully warm...i would think that this isn't exactly a good thing as fuel vapour is escaping somewhere. also the exhaust tip is quite blackened and sooty. Is this a sign of rich running?

I know this topic has been beaten to death countless times alerady, but any insight from the viffer gurus here would be appreciated on this...

thanks a bunch!
gab

Welcome to the site!

Check your fuel pressure regulator to see if it is leaking fuel through the diaphragm into the vacuum line, which connects to the throttle bodies.

Disconnect the vacuum line, run the bike, and check for fuel coming out the nipple on the hat of the regulator.

BTW, mine is a 1999 also and I get over 40 MPG routinely.

i had a vacuum leak. did terrible things to my mileage. also, check your sprocket gearing. if your are down(front) or up(rear) a tooth your odometer will think it is spinning faster than you are actually going. i think one tooth front is around 7%, while 2 rear is around the same. i think.

perhaps check for a fuel leak as the engine is running. someone here on vfrd, i think, had an issue like yours, and found a tiny pinhole leak that was only visible while the engine was running, and was so small it didn't show any signs of an actual leak. it just misted and vaporized immediately.

good luck!

btw, vfr's get terrible mileage.

Thanks for the replies guys!
I know the viffers are known for being thirsty. 32mpg isn't exactly worrying, neither is it something to be happy about, which it what makes this pretty annoying.
I'll start by checking the sprocket sizes when replacement is due, which is pretty soon. But dirtbag-wouldnt undergearing it as you have suggested cause the odo to over-read, "improving" the fuel mileage?
If the fuel pressure regulator is leaking, can it be serviced or should it be replaced?
Pinpointing a leak under all that plumbing will be a royal pain in the butt.

Thermostat stuck open?
Welcome

C

Easy to check the FPR, tilt the tank up, it's on the right side.

Take the vacuum hose off the hat and run the bike.

It's not serviceable, must be replaced if faulty.

From what i've gathered, it doesnt look like a stuck open thermostat at the moment because i'm getting good running temps, if a little on the high side. (it gets up to 110 deg C on a warm day in traffic) Fan is functioning normally too.
Will give the fuel pressure regulator a look through after my exams. Hopefully the issue is something that simple...

Shoot Rob beat me to it, yea the fuel pressure regulator might be the culprit. Mine started having issues at 120,000 miles so I replaced it, along with the fuel hose since it got jacked removing the FPR. I pretty much rebuilt the bike at 120,000 miles - removed the injectors, cleaned them, and replaced the seals on those too. Then it got totaled by a guy in a big blue van.

and you got a brand new bike!!! Beautiful ending, isn't it? :fing02: :laughing6-hehe:

YUP I did, still put a lot of work into the old girl right at the end.

But dirtbag-wouldnt undergearing it as you have suggested cause the odo to over-read, "improving" the fuel mileage?

thinking about this makes my head hurt... i think your right
:huh:
so i am getting really, really bad mileage...

:ohmy:

Thanks guys for the replies, it is indeed looking more and more like a fuel leak of some sort. there is a pretty strong smell of fresh fuel when the bike is hot, and it is quite clearly coming from the right side of the bike under the tank. Can't be 100% sure without verifying, but i get the feeling we are heading in the right direction.

also,the cranking time on a cold start (and cold in my country is hardly ever below 25 degrees C or 77F) is noticeably longer than most bikes i have owned, plus it stalls almost immediately without choke, exactly what was described here:
[video: https://youtube.com/embed/AKtR_yF7bi8?html5=1&fs=1]

The vehicle involved isn't a vfr or even a bike for that matter but i would imagine the symptoms are similar...

Update: I had a quick look under the tank today and did as veefercanuck suggested.

There is clearly a smell of fresh fuel (or very rich exhaust?) coming from the right side of the bike, somewhere near the rear cylinder head.

[image: Posted Image]

Here is a pic of my airbox. The hose on the bottom left is the crankcase breather hose; so its safe to say that engine oil buildup on the right side is pretty normal? The smaller hose indicated on the bottom right is the pressure regulator vacuum hose right? it does not seem to be leaking, after running the engine for several minutes.

Yes and yes.

Update: I had a quick look under the tank today and did as veefercanuck suggested.

There is clearly a smell of fresh fuel (or very rich exhaust?) coming from the right side of the bike, somewhere near the rear cylinder head.

[image: Posted Image]

Here is a pic of my airbox. The hose on the bottom left is the crankcase breather hose; so its safe to say that engine oil buildup on the right side is pretty normal? The smaller hose indicated on the bottom right is the pressure regulator vacuum hose right? it does not seem to be leaking, after running the engine for several minutes.

So, if the FPR diaphragm has failed, fuel will flow out of that nipple when the engine is running?

]So, if the FPR diaphragm has failed, fuel will flow out of that nipple when the engine is running?

Yes, it will leak out of that nipple. Also check your fuel return line to the tank, which is the black hose with the sheath you can see in your previous post. Check to make sure there are no leaks anywhere along that hose.

Also a leaky fuel injector is a possibility. I have a video on YouTube which explains how to look for leaky injectors.

[video: https://youtube.com/embed/iuCdrZ6lF6I?html5=1&fs=1]

Thanks very much!