okay when my tank is 3/4 full i have to switch to res. this is the third time this has happened. i even zero my odometer when i fill up.

after about 70-80 miles i am riding and bike starves... i have to switch to res.
i open the tank and it us 3/4 full

any idea what causes this?

Fuel starvation can be caused by...

- Pinched fuel lines
- added fuel filters
- clogged vent in gas cap

There are other reasons, but based on you being able to run in res I'll go with these. Such as... added fuel filter on main line that is not on res line; slightly pinched main line while res line has no restrictions.

So, do you have added fuel filters? Have you check your hose routing to make sure all is well? Lines can get a small pinch point in them if the tank has been lifted to do work and whatnot.

Michael

Quote from: mister on July 01, 2012, 10:54:10 PM
Fuel starvation can be caused by...

- Pinched fuel lines
- added fuel filters
- clogged vent in gas cap

There are other reasons, but based on you being able to run in res I'll go with these. Such as... added fuel filter on main line that is not on res line; slightly pinched main line while res line has no restrictions.

So, do you have added fuel filters? Have you check your hose routing to make sure all is well? Lines can get a small pinch point in them if the tank has been lifted to do work and whatnot.

Michael

no i dont have added fuel filter. but i did lift my tank last week to change my jets.
so maybe the fuel lines got moved?

the clogged vent makes sense too. there would be no air pressure inside so the vacuum wouldn work once the fuel drops a bit.... if thats the case then after another 70-80 miles the the shouldnt work either..,

am i right in that theory?

If you can go 70 miles, than it's probably not your gas vent.  Look at the carb float vent.  It's the one that routes on the top of the stock airbox.  That has caused me to stall when it gets pinched.  Wait a while, and it works again.

How old are your fuel lines?  They may be getting weak and collapsing on you perhaps?  Is your tank petcock shutoff straight up and down?  Is your tank petcock screen clogged?  Is there debris in the tank?

Quote from: jestercinti on July 02, 2012, 07:25:07 AM
If you can go 70 miles, than it's probably not your gas vent.  Look at the carb float vent.  It's the one that routes on the top of the stock airbox.  That has caused me to stall when it gets pinched.  Wait a while, and it works again.

How old are your fuel lines?  They may be getting weak and collapsing on you perhaps?  Is your tank petcock shutoff straight up and down?  Is your tank petcock screen clogged?  Is there debris in the tank?

okay but if it was the carb float vent then why does it run when i go to reserve?

i will recheck all lines today. my fuel lines are old but again if it was the lines then it would effect it under res too no?

From the tank, On comes out one fuel line.  Reserve comes out of a different fuel line. 

ok here is a dumb question....

i recently rejetted to 40/125
put on a 15t front sprocket
ignition advancer
have a k&n drop in

can it be that my fuel economy is gone down from these mods, so that i need to go to reserve at 100-105 miles?
and my fuel lines are actually ok?

Easy to tell.  Just see how much gas you have to put in.  it's possible that you are running rich, but I wouldn't say it's because of the jets.  I plan on running 127.5 jets when I switch to the K&N drop-in.  I'm running 125/40 jets now on the stock filter and getting 49 mpg.  Check to make sure your floats didn't get mess up when you were re-jetting.  High gas level in the bowl will cause it to run rich.

All those mentioned above reduce fuel economy.  I can't say how much because there are other things that cause poor fuel economy like heavy throttle, poorly inflated tires, headwinds, poorly tuned engine, etc.  All the above in addition to what I mentioned will cause lower fuel economy.

So yes, it's absolutely possible.

#5010

How full are you filling the tank? Are you watching and filling it to the fill tube? Sticking a gas pump in there will shut off the pump with room for a gallon more. Its not like a car with a foot of pipe above the gas tank. You have to hold the nozzle  out to top off your tank.

Then, most gas is in the upper part. You may think you have half a tank when there's only a gallon left. The bottom of the tank tapers. The top bulges out.When you looking it may seem half full when its much less.

Another think to do is measure your mileage. Maybe you're getting really bad mileage now. Maybe you have a slow leak? Do you smell gas? Do you see any drips? Feel the fuel lines. Are they wet? Old lines can crack or come lose when you work on things.

Suggestion: When working on a bike with old fuel lines, replace them and make them longer so you have more line to flex and more when lifting up the tank before they get tight or come off. Phenix's lines are quite noticeable. They are longer - with plenty to route around things without them getting pinched.

You can see them here. maybe later I'll shorten them an inch or so just for appearance, but still leave them longer than OEM length.

ok so i filled up today and i did some math conversion from liters to
gallons

as soon as i switched to res i went to a gas station and:

i put 11.5 +/- liters in the tank ,
which is about 3 gallons of gas... and the mileage i got out of that 3 gallons is about 100-105 miles.

so how does that sound in terms of mileage and the res issue? the tank is 4.5 gallons.. is it normal to switch to res with roughly 1.5 gallons left?

also forget to mention this is stop and go city driving. i ussually rev up to 7000k and change to next gear

#5015

You're about right on for switching to reserve. How you fill the tank and what angle the bike is on can make a 1/2 gallon difference. Go a couple more fills then average it.  You've got kind of low mileage and too much reserve - so average over a few fills.

City (stock bike) I get about 45-50 mpg. Most gas used just starting bike before going only a half a mile then stopping. Highway I get over 65.

Spec says tank capacity is 17L or 4.5 gallons. Reserve amount is 3.5L or 0.9 gallons. So that's why I suggest averaging over a few fills. (Spec for 89-00 tanks)

You rev too high. Rarely over 5k RPM in normal and city riding. Even Vashon twisties up hill - I don't think I ever hit 6k.  I think you're wasting fuel just making the engine go. City cruising is 3.5k to 4.5k - depending on the slope of the road. No need to be at 7k RPM when going 20 mph.

Quote from: adidasguy on July 02, 2012, 04:08:48 PM
#5015

You're about right on for switching to reserve. How you fill the tank and what angle the bike is on can make a 1/2 gallon difference. Go a couple more fills then average it.  You've got kind of low mileage and too much reserve - so average over a few fills.

City (stock bike) I get about 45-50 mpg. Most gas used just starting bike before going only a half a mile then stopping. Highway I get over 65.

Spec says tank capacity is 17L or 4.5 gallons. Reserve amount is 3.5L or 0.9 gallons. So that's why I suggest averaging over a few fills. (Spec for 89-00 tanks)

You rev too high. Rarely over 5k RPM in normal and city riding. Even Vashon twisties up hill - I don't think I ever hit 6k.  I think you're wasting fuel just making the engine go. City cruising is 3.5k to 4.5k - depending on the slope of the road. No need to be at 7k RPM when going 20 mph.

i will watch for it a few more times. i normally fill with bike on side stand.. i do not have any leaks i checked

i do believe the 15t sprocket effected my mileage because it revs higher quicker. and i am at fault too because i like accelerating fast from a stop sign or lights

Fill bike on center stand. More gas will fill the tank.  You'll get more miles out of it. Also, lower teeth sprocket will lower gas mileage.

cbcanada,

The more info the better.... revving to 7k before changing, 15tooth front sprocket. Yeah, your riding style is effecting your economy.

Stock 16 sprocket, normal gear changes 5000 to 5,500 is all you need. Do jackrabbit starts and gear changes and your fuel economy goes to sh!t. You're doing everything possible to have bad fuel economy.

Fill on center stand gives you a more even fill. Fill until it starts to come up the neck and stop. it will go down then and you can, if you want, trickle more in. But there is no point. Filling up this way is pretty consistent and will give you a truer idea on your fuel economy.

Michael

some of these "problems" are just too funny!

What year is your GS500?

Mine is '91. When driving inside the city I use to get 160Km (100Miles) from a tank, (not counting reserve). When I re-fill the tank it only gets 10.5 litres

I've been able to fill the tank with 17 litres so normal tank is 10.5 litres and reserve is 6.5 litres.

6 or 6.5 litres per 100Km is not bad when driving inside a city.

I use to get 4.2l/100Km on road/highway. Stock jets, stock air filter, 17 teeth sprocket, 96000Km on the counter.

Quote from: marc on July 03, 2012, 06:08:48 AM
What year is your GS500?

Mine is '91. When driving inside the city I use to get 160Km (100Miles) from a tank, (not counting reserve). When I re-fill the tank it only gets 10.5 litres

I've been able to fill the tank with 17 litres so normal tank is 10.5 litres and reserve is 6.5 litres.

6 or 6.5 litres per 100Km is not bad when driving inside a city.

I use to get 4.2l/100Km on road/highway. Stock jets, stock air filter, 17 teeth sprocket, 96000Km on the counter.

mine is a 1999.
wow yours was like mine and you were stock.. okay i dont feel so bad now.
before i did the mods i used to get much better economy. then i did all the mods over the course of one week and then real noticed the fuel economy difference... so much so that i thought i had fuel starvation problems as appearant in my OP