Bad mpg?

[motolover]

Hello again,guys. My ride is FJ 1100 1984. .This bike is very good in mpg outside the city.Usually i reach 40 mpg,but when i ride in the city things are going worst...
in the city my mpg is 25 mpg...It is nearly double
My needles are in the downest position....My plugs are iridium....I'm very light on the throttle..My main jets are stock...
Any suggestions,fellows?Thanks...

[the fan]

What part of the world are you in? US model FJ's do not have adjustable needles, not sure about elsewhere.

[FeralJuggernaut]

I get about 30 in the city and 32 on the highway.   I can sneak out 35 if I keep it within the posted signage, but who among us is capable of that feat for very long?!?    Here is a thought,  when was the last time you rebuilt your front and rear brake calipers?   I let mine go for quite awhile, and when I redid them last summer I found that one piston in each caliper was 'frozen' in place and it was dragging on the disk quite a bit.   I would think it effects both city and hwy mileage equally, but it is a worthy question anyway.

The only other thing I can come up with is in the carbs.   city driving leaves you running on the idle and mid range circuits.   how far out are your idle mix screws?   I like mine about 2.5 turns out, but one of them have been ham fisted to it doesn't calibrate like the other three.   Also, when was your last carb sync?  If they were way out, it could be beneficial to do the sync again.   Frank suggests that sync should be an annual party for best results.

What kind of fuel do you run?   I use 91 octane, others think 87 is good enough. 

If you can find Lee C... he has 200K miles on his '84 and runs in the mid to high 40s regularly and into the 50mpg occasionally.  Seek his council too.   I find him on the yahoo group most of the time and netpath(now micapeak) occasionally.  He has a soft spot for the red and silver bikes.   

[paulfj03]

I am interested in this topic as well ...Ive noticed the gas mileage is not too good on my 91..the last tank gave me approx. 150 miles.  I use the 91 Octane.  I got so much on my list that I'm not going to worry about it until the winter. I'll check the calipers ( i never thought of that.) and clean the carbs.  and then I'll go from there.
I get close to 400kms or 250 miles with the 1100(larger tank..but still...) while driving it hard now and then, so I know there is a problem with the 91. thanks for the tips guys.

[SlowOldGuy]

Check the needle jets (emulsion tubes).  Sometimes with a lot of miles, the tubes get "ovaled" by the needles banging back and forth which can deratically richen up the mixture and send mileage into the toilet.

DavidR.

[Dan Filetti]

Check the needle jets (emulsion tubes).  Sometimes with a lot of miles, the tubes get "ovaled" by the needles banging back and forth which can deratically richen up the mixture and send mileage into the toilet.

DavidR.

Ah, this partially answers a question I was asking a few months ago, 'is it possible for carbs to 'wear-out [mechanically]?', it was in reference to someone saying their carbs were old and worn-out, and may need replacing.  -you were MIA long about then I guess Dave. 

From your answer above it sure does seem like there is a possibility they can wear out, or at least the needle jets may need to be replaced, which oh, by-the-by, seems cheaper than replacing the carbs entirely...

I'll ask the question again, in more general terms, are there other parts on the carbs that you've seen wear-out possibly even to the point of actually needing to replace the carbs?

Curious.

Thanks,

Dan

[Sturgis_Bryan]

I had to replace my emulsion tubes at 44K. If you don't have a way to measure the hole you can do a visual inspection. with the bike at idle and the air box removed you will be able to see a small puddle of gas where it exits the emulsion tube. With new emulsion tubes I no longer see the puddle. According to the tec at factory pro, any out of round condition will cause it to run rich.

[racerrad8]

The main wearing "hard part"' items of the carbs are in the one circuit...The vacuum adjustable mixture circuit. This circuit includes the brass emulsion tube, the aluminum needle, and the rubber slide diaphragm.

Not only do the emulsion tubes wear, the needle which is causing the wear on the tubes as also wearing. I recommend changing them as a set. If you do purchase the "Nickel" coated emulsion tubes from Factory Pro, expect to replace the needles 3 to 1.

I have upgraded adjustable O.E. needles and emulsion tubes in stock.

Randy - RPM

[racerman_27410]

Randy. do you also have the small o-ringsfor the mixture screws?

i need to place another order for the emulsion tubes and needles.

Frank

[racerrad8]

Not individually...yet...I have been working on it, but am having trouble finding a supplier. The company I get all of my other metric o-rings from don't have anything that small.

I do have them in the idle needle sets. Unfortunately, I have to sell someone a needle set when the o-rings is damaged or missing.

Give me call and I can get the other parts on the way.

I'm headed out for a quick bite of lunch right now, back in about 45 mins.

Randy - RPM

[racerman_27410]

Sure thing Randy.


Frank

[SlowOldGuy]

3mm X 1mm from McMaster-Carr

I think I have some extras.  PM me your address; RAFORTHDL@aol.com.  You still in Greensboro?

DavidR.