80 miles on a full tank?

Hey everyone. Just picked up a 1991 750. 19000 miles. just had everything done... oil,plugs,carb clean,air filter,coolant.. etc
Well, im gettin 80 0r 90 miles till i have to fill up again!!!!! no fuel smells, no leaks. Anyone heard of this B4?

Sounds like it's running super-duper rich.  Have you owned a VFR before so you can compare this bike to previous experience (with regards to its power delivery)?

When you did a "carb clean", what did that include?

How many gallons on the fillups, average?

well it has a kerker left hand exhaust and i thought mabe no one jetted it. so i took it to my local shop and they said that it needed a carb cleaning. not sure what they did. it runs good but pops a little because the aftermarket exhaust. but no. this is my first vfr so cant compair. but dosent smell real rich either. what should i be getting?

3.5-4 gal average

where did u guys go!

helllllllllllllp!!!!

I can't figure what could cause the consumption to be so high. It must be running very poorly if there are no leaks. What is the running temp of the engine? A bad thermostat can cause poor economy butI would not think it would be this bad.

i know! its real bad most people think im mistaken. runs just under half most of the time. IDK im real lost111

it really only gets like 87 average. its like a full size truck! lol... not that funny

lets see..
1st.. pull the tank.
2nd . remove the 2 rear plugs .. the should be a tan to brown color.. black or sooty means too rich.
white is too lean.

after you do that PM me .

Is this a California bike?

My 91 gets about 40 mpg (+/- 5 but it depends on running it hard or goin real easy).  I think mine is running a bit rich lately as it backfires alot when I allow the engine to slow the bike down. I'm told this is a symptom of being set too rich.

So your getting 25-30 mpg it sounds like. I think I'd start by checking your plugs for signs of fouling. If everything looks good, I'd check electrical to include the R/R.

no. not a caliofornia bike. New york.... your thinkin because of emmissions controls?

lahn... what is R&R... do i sound dumb? u guys know all the lingo.... lol

what does a '91 have for vacuum hoses?  i would try and pull a diagram and got through all your vacuum lines... and check your tees!  i just had a 5way tee crack on my '02, and it was giving me miserable mileage... but not as bad as yours.

[image: View Post]nevermind, on 28 June 2012 - 07:20 PM, said:

no fuel smells, no leaks. Anyone heard of this B4?
On mine the fuel hose was leaking (deteriorated from age) but there was no gas smell as the fuel dripped on the hot rear header and most had evaporated before it was parked in the shed.

[image: Posted Image]

Also check if it is running on all 4 cilinders. You can check by touching the downpipes immediately after the engine runs, they should all get hot pretty quick. Next also feel if the radiator or water hoses warm up quickly, that could indicate a stuck (open) thermostat. The VFR engine like to run hot. The choke cable is in perfect working condition?

Unless you are doing nothing but max speed runs on a deserted highway, you should be able to ride at least some 275km.



A dutch bike magazine did top speed runs on a few bikes, including the VFR1200 on a german autobahn (no speed limits). The fuel light came on after 80kms.....  I think they logged 280kmh top...

If you just paid a shop to have the motorcycle serviced and the carburetors cleaned and adjusted you should take it back to them and register a complaint.

I'm wondering if the cold start/fuel enrichener circuits for one or more carburetors might be leaking or incorrectly adjusted and causing one or more cylinders to be running way too rich. Only 80-85 miles per tank is less than half what you should be seeing unless you're riding w/the throttle pinned most of the time. I generally get 45-50 mpg, or 225+ miles out of ~5 gallons from my 5th-generation. Note that I'm assuming you are being careful to turn off the choke/fuel enrichener control completely on the handlebar within 30 seconds, or less after each cold start.

If the shop finds the caburetors are not set up right make sure they also replace the spark plugs (at their expense) for it's more-than-likely they're already carbon-fouled. I'd also recommend checking the motor oil for evidence of fuel dilution and have the motor oil and oil filter changed again (also at their expense) if necessary. If the motor is running way too rich it's likely some of the excess gas has been making its way into the motor oil.

Also, if you bike has a manual fuel shutoff I recommend you be careful to shut off the gas each time you turn off the engine until these issues have been resolved, for it's possible fuel could be leaking from the carburetors and running into the cylinders when the engine isn't running. This represents a serious threat, for if fuel leaks and pools in one or more cylinders your engine could suffer catastropic damage when you try to start it.

Liquids don't compress!

When are you refuelling the bike?  My gas gauge shows E after about 120-130 miles, even though I have a good two gallons left.  It seems to be common to have a premature gauge.  When you are filling up, how many gallons are you putting in?

[image: View Post]mk2davis, on 29 June 2012 - 10:55 AM, said:

When are you refuelling the bike?  My gas gauge shows E after about 120-130 miles, even though I have a good two gallons left.  It seems to be common to have a premature gauge.  When you are filling up, how many gallons are you putting in?
In an earlier post he indicated 3.5-4 gallons, which only correlates to 25 mpg or less.

87 miles / 3.5 gallons = 24.86 mpg
87 miles / 4 gallons = 21.76 mpg

So he did.  Not sure how I missed that.

The no smell thing is really throwing me.  I'd think if it was an open carb circuit, horribly wrong jets, sticky choke, etc., I'd think it would smell really rich.  Pulling the carbs is a good way to check, as someone already suggested.  As V4 stated, I'd check hoses between the pump and the carb.  Maybe something is leaking only under pressure (even if it's only the 2-3psi).  When the bike isn't running, less pressure, leak goes away?

Does it feel like a 750 or does it feel like a 600 when you accelerate?

Or maybe a 450....it has to be passing a bunch of unburned fuel through one or two cyclinders and the result is you flogging the throttle to keep it up to speed...have you pulled the plugs yet?

hey guys. thanks for the replies!!! im still pretty screwed at this point. i havent checked hoses yet will do that soon. NO GAS SMELL!! very odd. oil smells very good. has that fresh new oil smell.    (one of the best smells on earth other than tire smoke)    absolutly no gas smell in oil.. does not need choke to start even when cold. well that is not saying much because its been in the 90s all week. i will check choke cable but the bike dosent smell rich. BTW how many gallons does the tank hold because the light goes on and i put in 3.2 to 3.4 gallons. Thanks again guys. we will get to the bottom of this!!!

i believe thermostat is working. the temp is around the middle and fans come on when too hot

[image: View Post]nevermind, on 29 June 2012 - 07:39 PM, said:

BTW how many gallons does the tank hold because the light goes on and i put in 3.2 to 3.4 gallons.

19.00 litres (5.02 gallons)

How are you measuring your mileage per gallon?

Rollin

well.. i fill it up then i go till the light comes on. then it takes about 3.5 gal and trip meter says about 87 average. im not nice to her... but im not bouncing it off the rev limit either. thats how i measure 87 devided by 3.4 equals 25.5... my elcamino gets 24 on highway!!!!!!!!!!!!!!!!!!!!!!!!!! wtf

sombody has to have had this problem before!!!! i hope im not alone.

HAVE YOU PULLED YOUR PLUGS YET?

if so post up a pic of them.

i will post a pic of plugs 2morrow. been ridin all day 92 miles and put in 3.5 gal!

Here's my guess: carb bowl plugs aren't tightened all the way, causing gas to constantly leak

[image: View Post]cbkenison, on 30 June 2012 - 08:32 PM, said:

Here's my guess: carb bowl plugs aren't tightened all the way, causing gas to constantly leak
he said no gas smell..
however.. a quick test.. ride your bike for a few min... the feel the bottom of the carbs..are they wet? even a little?

booger

Be happy you only pay some 3-4 bucks a gallon...

;-)

Sorry, just saw this thread.  Nevermind, this was what was happening to me last season.  I would only get about 100 miles and then the fuel light would come on.  I figured I was getting about 28 mpg last season.  I also had a problem with my temperature gauge to the point that it wasn't reading correctly.  The fan was comming on and keeping things cool, it just wouldn't read right.  This season, I removed the carbs and all the rubber and did the pine sol soak.  I also went with smaller jets.  Books say I'm supposed to have 130 main's with 38 slow.  This season I basically made it a 94 California model with 125/128 but still kept the 38s.  The only mods I have are a K&N air filter and a Yoshi slip on.  After I cleaned the carbs I spent hours getting the carbs sync'd to within a gnats ass of each other.  I rode the other day and the fuel light came on at 170 miles.  I filled up at 180 miles and only put in 3.92 gallons.  I worked the numbers and that's 45.9 mpg.  The only other thing I did was replace the temperature sensor for the cooling system gauge.  Let me know if you have any other questions.

Adam

Nevermind, the R/R is your regulator and rectifier. It is a switch under the seat on the right side of the bike.  You'll need to remove the large Allen bolt on the rear right fairing to see it. They are notoriously hot so they burn out routinely and replacement parts are available from Honda but several people have gone to the Yamaha R/R as they run cooler.

still no luck. reaklly thinkin about gettin rid if this bike

What did the shop that worked on your bike say?  If you paid them a bunch of money to get your bike running properly, they haven't finished the job, have they?

Ciao,

Still no pictures of the plugs.  I will buy it, how much you want?

[image: View Post]Dutchy, on 01 July 2012 - 02:49 AM, said:

Be happy you only pay some 3-4 bucks a gallon...

;-)

I'm a little offtopic, look how many tanks of fuel you get in Europe with a minimum wage (a tank of 40 liters, or 10.5 gallons). Bicycle...here i come !

I get about 150 miles per tank, but I also have a high flow air filter, a Stage 1 jet kit installed, and a racing exhaust on my VFR. I'm also not very gentle with her at all, when I did the track day at Spa-Francorchamps in April, I was constantly bouncing off the rev limiter in 3rd, 4th and 5th gears.

I don't really care about mileage too much though, for me, it's about enjoying the ride. Although stopping for gas every 80 miles would get old really quick.

You might also want to check the condition of your chain for frozen/dead links, wheel bearings and brake rotors, as increased drag in these components can make the engine work harder.

You may want to double check your mileage against GPS, your odometer might not be correct.

So was the topic author found the problem? I am experiencing the same problem !