Carb trouble

[gazpacho]

Hey folks, my new FJ 1200 is using a massive amount of fuel, around 18mpg! If the photo has come out correctly you can see it has cut down open cans. The air filter is stock and there's no other mods, has anyone had a similar problem and how did you overcome it? I love this bike, it sounds awesome and turns heads but I cant afford to ride it if the fuel is gonna go this fast

[gazpacho]

note to self: move thumb before taking photo

[racerman_27410]

are you sure the gas isnt pouring out on the ground?  Going into the oil?


if the jets were stock with your setup then the bike should be lean, not rich.

i am going to go ahead and assume that a previous owner has installed jets that are waaaay to large.   Only one way to find out what's in there and thats to remove the carbs and take out the jets for a look-see. After you know whats in there we can get you all sorted on what to put back .......there is no reason a FJ cannot get at least 30mpg no matter how hard you are caning it.....mid 40's+ if riding for it.

I average between 35 and 40mpg usually.

KOokaloo! 

[The General]

Nice Bike and can actually understand the colour choice. But you really have to mount the Grill plate closer to the exhausts for optimal cooking. (unless those lights let out microwaves)
Mate, sounds like you`ll be busy this weekend playing with carbs. Let us know what you find.

[gazpacho]

are you sure the gas isnt pouring out on the ground?  Going into the oil?


if the jets were stock with your setup then the bike should be lean, not rich.

i am going to go ahead and assume that a previous owner has installed jets that are waaaay to large.   Only one way to find out what's in there and thats to remove the carbs and take out the jets for a look-see. After you know whats in there we can get you all sorted on what to put back .......there is no reason a FJ cannot get at least 30mpg no matter how hard you are caning it.....mid 40's+ if riding for it.

I average between 35 and 40mpg usually.

KOokaloo! 

right..... you have confirmed a suspicion i had, i changed the oil Saturday and it was like water. Just had a sniff of the old oil in the shed, its full of bloody petrol! so... next question, how would petrol leak into the oil?

[gazpacho]

Nice Bike and can actually understand the colour choice. But you really have to mount the Grill plate closer to the exhausts for optimal cooking. (unless those lights let out microwaves)
Mate, sounds like you`ll be busy this weekend playing with carbs. Let us know what you find.

lol! the grill serves no purpose whatsoever, i was going for a madmax theme. Got a mate with some thicker grill which will actually bear weight instead of flapping around lol

[Harvy]

next question, how would petrol leak into the oil?

It runs down the carb throat, through the manifolds into the cylinders, past the piston rings and on down into the oil.
As Frank said, pull the carbs and check out your jets. Also check float height as its getting way too much fuel. Let us know what you find.

Harvy

[racerman_27410]

next question, how would petrol leak into the oil?

It runs down the carb throat, through the manifolds into the cylinders, past the piston rings and on down into the oil.
As Frank said, pull the carbs and check out your jets. Also check float height as its getting way too much fuel. Let us know what you find.

Harvy

leaky float needle valves and or shot needle valve o-rings can also cause the gas to run into the engine or out on the ground or both.   it really messes up the fuel mileage as you have found.

you have to get in there to find out what it is for sure though.

good thing these carbs are such a joy to work on. 

KOokaloo!

Frank

[Dan Filetti]

leaky float needle valves and or shot needle valve o-rings can also cause the gas to run into the engine or out on the ground or both. 
Frank

That, yes.  But 'upstream' of that the petcock has failed as well.  It must have.  Failure #1: Petcock, #2: needle seat o-rings as above.  Seems to me both need to fail to wind up with fuel in the oil. 

Dan

[Harvy]

leaky float needle valves and or shot needle valve o-rings can also cause the gas to run into the engine or out on the ground or both. 
Frank

That, yes.  But 'upstream' of that the petcock has failed as well.  It must have.  Failure #1: Petcock, #2: needle seat o-rings as above.  Seems to me both need to fail to wind up with fuel in the oil. 

Dan

Hard to tell if its a gravity feed model or not..... the forks and calipers suggest its an '88 or '89 model which had me thinking fuel pump Dan.

Cheer
Harvy

[Dan Filetti]

Hard to tell if its a gravity feed model or not..... the forks and calipers suggest its an '88 or '89 model which had me thinking fuel pump Dan.

Cheers
Harvy

Ok. But even if it's a fuel pump model, with the bike not running, the pump is not pumping and indeed, should be sealing and not flowing any fuel -no?

Surely the fuel pump models do not do away with the 'first line of defense' in bike-off-fuel-flow-prevention'?  If this is the case, it would mean that the only barrier to fuel in the oil, is that one little O-ring in each of the carbs...  Say it ain't so...

Please confirm.

Dan   

[Harvy]

Hard to tell if its a gravity feed model or not..... the forks and calipers suggest its an '88 or '89 model which had me thinking fuel pump Dan.

Cheers
Harvy

Ok. But even if it's a fuel pump model, with the bike not running, the pump is not pumping and indeed, should be sealing and not flowing any fuel -no?

Surely the fuel pump models do not do away with the 'first line of defense' in bike-off-fuel-flow-prevention'?  If this is the case, it would mean that the only barrier to fuel in the oil, is that one little O-ring in each of the carbs...  Say it ain't so...

Please confirm.

Dan   

Dan, on '91+ models (can't speak for earlier) the pump is the only thing stopping flow when the bike is not running. The petcock is always on unless you lift the tank and turn the little plastic shut off skeg........ only done when you have the side covers and tank removed for work on the fuel pump.

SO yes, the o-rings hold back the fuel if the pump fails in an open flow condition (I don't know if this is possible???)..


To explain in another way..... if you do not touch the petcock tap, disconnect the fuel line from the pump outlet, fuel will not flow until you turn on the key (assuming the pump is not faulty).

Harvy

[Dan Filetti]

Harvey-

Sounds like we're saying the same thing.  

With the bike off, both the gravity fed, and fuel pump models have 2 lines of defense when attempting to prevent fuel winding up in the oil.

Gravity:         1) Petcock -no vacuum    2) Needle Seat O-rings
Fuel Pump:     1) Fuel Pump itself          2) Needle Seat O-rings

In both cases, both must fail (that is: allow fuel to pass through with the bike off when they are not supposed to), for fuel to wind up in the oil.  

Cheers!

Dan

[Harvy]

Harvey-

Sounds like we're saying the same thing.  

With the bike off, both the gravity fed, and fuel pump models have 2 lines of defense when attempting to prevent fuel winding up in the oil.

Gravity:         1) Petcock -no vacuum    2) Needle Seat O-rings
Fuel Pump:     1) Fuel Pump itself          2) Needle Seat O-rings

In both cases, both must fail (that is: allow fuel to pass through with the bike off when they are not supposed to), for fuel to wind up in the oil.  

Cheers!

Dan

Yep....we are in agreement.....this could be a first.....lol