Runs GREAT, horrible gas mileage

[ih781000]

I have a 91 FJ1200 I bought a little over a month ago. Only 17,000 miles. This thing runs incredibly good. No cold start problems. Sounds really smooth. I'm averaging about 27 mpg and I ride it easy. Is this normal for this model?

[aviationfred]

Running well, not difficult to start, comes off of choke quickly, no backfiring when the throttle is chopped. I would say the carbs are ok, and to check the size of your sprockets.

OEM rear sprocket is 40 teeth. The front OEM should be a 17 tooth sprocket. My guess would be that you have a 47 tooth rear sprocket.

Fred

[racerrad8]

No, 40+ MPG is the norm. If the sprockets as Fred mentioned are stock, then you definitely have a carb issue.

Randy - RPM

[andyoutandabout]

My 86 runs an 18 front 46 rear and regularly gets 42mpg regardless of how I ride it. Sounds like yours is too thirsty. Perhaps it's the float heights - Pat? Randy?

[Bones]

My 86 runs an 18 front 46 rear and regularly gets 42mpg regardless of how I ride it. Sounds like yours is too thirsty. Perhaps it's the float heights - Pat? Randy?

46 tooth rear sprocket !!! It'd be great for acceleration, but what's it like on the highway, I'm always clicking up thinking I'm in fourth gear, and that's with a 17/39 combo.

                                                                     Tony.

[Bozo]

When I first bought the FJ1200 I had crap economy (around 30mpg imp), the standard air filter / box were the problem, once I got rid of these 350/400km (normal touring) per tank full is the norm (1989 3CV). I'm not saying this is your problem but its worth considering.

[FJmonkey]

Wow!  At 27 MPG you must be dumping fuel on the ground. I have 18/38 gearing and getting better than 45 MPG. I was getting closer to 50 MPG with stock pipes and air box. Now I have UNI pods, Supper Trap slip-ons and re-jetted carbs. Start with the simple stuff, make sure your choke turns off fully. Having this partially on will suck more fule than normal. Float levels can be checked with the carbs on, just need some clear tubing that fits the drain tube on the bowl.

[red]

Wow!  At 27 MPG you must be dumping fuel on the ground. I have 18/38 gearing and getting better than 45 MPG. Start with the simple stuff, make sure your choke turns off fully. Having this partially on will suck more fule than normal. Float levels can be checked with the carbs on, just need some clear tubing that fits the drain tube on the bowl.

ih78100,

The FJmonkey may be onto the real issue here, which could be the choke system sticking, or a cracked fuel line or fuel connection, somewhere.  Check everything for leaks, from the tank to the carbs, even the hard tubing which the fuel lines run into.  Turn on the key (do not start the engine), to get your fuel pump into the act.  Even if you do not see gas leaking, if the fuel pump keeps running slowly, you have a leak somewhere.  You may have one bad needle-and-seat, also.  If you keep hearing the fuel pump, and can not find a leak, block off the fuel lines into the carbs, and see if that will stop the fuel pump.  If the leak continues (fuel pump still runs), at least you will know that the needles-and-seats are not the problem, then.  If all that checks out good, then you may have a carb float problem.  Let us know what you find.

Cheers,
Red

[ih781000]

When I turn on the key, the fuel pump comes on for a second or two then pressures up and stops. When cold and the choke is completely off, the bike idles at around 300 rpm, warmed up around 1000 rpm. Don't think the choke is the issue but could be. I don't smell any gas around the bike when first started or when getting off after a ride. Don't see any leaks below the bike after sitting all day at work or all night at home. Maybe it's the gearing. At 55mph i'm running close to 4500 rpms in 5th gear. Hate to get into the carbs since it runs like a cherry other than sucking gas like a dang car.

[movenon]

When I turn on the key, the fuel pump comes on for a second or two then pressures up and stops. When cold and the choke is completely off, the bike idles at around 300 rpm, warmed up around 1000 rpm. Don't think the choke is the issue but could be. I don't smell any gas around the bike when first started or when getting off after a ride. Don't see any leaks below the bike after sitting all day at work or all night at home. Maybe it's the gearing. At 55mph i'm running close to 4500 rpms in 5th gear. Hate to get into the carbs since it runs like a cherry other than sucking gas like a dang car.

What kind of riding? Around town stop and go or freeway?
George

[FJmonkey]

At 70 MPH my RPMs are around 3500, your gearing is affecting some of your mileage but not all of it. Mike "Skymasteres" rode with me on Sunday with gearing similar to yours based on speed and RPM and his mileage was only slightly worse than mine.

[fj1289]

From the list of bikes in your sig, I'm going to assume you spin wrenches and know your way around bikes in general. 

Sounds like the bike is very rich at idle - especially if it starts without choke (and stays running at 300 RPM - holy cam chain backlash batman!).  Being that rich at idle will definitely kill gas mileage - especially around town.

First, like has been covered, make sure the chokes are off. Based on the 300 RPM idle cold, I'm thinking he "chokes" are off (the FJ "choke" is an enrichment circuit that supplies a lot more fuel to richer the mixture AND supplies more air for a fast idle while it warms up). 

I see the pipe - do you have stock air box or pod air filters?

Do you know if the PO installed a jet kit?  Or rejetted the carbs?  I'd so, do you know the jet kit installed?  Which company the needles are from?   If the pilot jet was changed?

Most importantly - when warmed up - how does it respond to the blip test?  Give the throttle a good blip at idle and watch how the engine returns to idle. If it hangs above idle for a moment and then settles back down, then it is lean -- try a 1/4 turn out on the idle mixture.  Repeat.  (Really don't think will be the issue from your description!).
If it drops below idle speed momentarily and then climbs back up, it is rich --  turn the idle screws in 1/4 turn to lean the idle.  Repeat.  (Note - the idle screws are fuel screws, not air bleed screws as on some other carbs you may be familiar with).  I wouldn't make more than a 1/2 turn total change without a good test ride.  If it runs good, then try another 1/4 turn.   Repeat until you are happy with it or it starts running worse at that engine range (idle to about 1/3 to 1/2 throttle).  If the idle is as rich as it sounds like it is, you may have to make a small needle adjustment if the PO has lowered the needle trying to compensate for too rich of an idle.   

Best results will come from synching the carbs (and a good cleaning - almost can't clean them enough...). 

Lots of good carb info in the files section too

Good luck and please let us know how it's going. 

[ih781000]

Thanks for all the replies. Sounds like a little wrenching is in order this weekend. Will let you know the outcome. (May not happen this weekend as we are expecting snow and ice Thursday thru Saturday so I could not test drive)

[andyb]

That sort of result usually means a simple leak.

Be interesting to see what you come up with.

[chiz]

I just saw this thread boy oh boy my bike eats gas as well and I thought it ran splendidly It needs choke to start when cold blips nicely when warm. I think the fuel gauge is bonkers but when I throw $15.0 in the tank and bring the fuel up to a little below the filler and ride a few klicks its back down to where I started.
I got to travel with cash all the time with this bike I worry about getting stranded.
Chiz