Burning too much fuel

Hi folks.

Just new on here and hoping to get some advice. I just bought my wife an xj 650 1981 maxim. Its in immaculate shape and she loves it. It rides and starts like a dream but for some reason we are only getting 120km or less out of a tank of fuel. I would figure they wouldn't burn that much gas. I'm thinking something has to be wrong. Any help or things I can modify I would sure appreciate.

Thanks so much.

 

Have you taken the plugs out and check the color? Post a pic so we can see. I don't know what to expect in mileage from a 650, but that seems a little low. It might be time to remove the carbs for a cleaning and tune. Check the air filter also.

 

My bike burns fuel fast when driven fast.
Maybe ask her to try slowing down

 

i had that bike when they were actually being sold. mine got 60 mpg. i had another one up till 2 months ago. it only got 35 mpg. compression was decent but not as good as it should be. but piston rings had blowby. oil fumes were going into the airbox.

pull your breather tube from the engine to air filter box and see if you got any blowby smoke coming out. check your compression also. mine had 140 in all 4's. i know someone that is driving one around. he rebuilt the top end. he has 165 pounds compression and is getting around 53 mpg.

 

You getting roughly 30mpg right now.

That's reasonable.
Scrub the Diaphragm Piston Bores.
Vacuum Clean or Compressed Air Blow Clean the Air Filter.
Monitor the Spark Plugs.
If the Plugs are Dark ... Lean the Mixture 2-Degrees at a time until the Plugs are the Color of a Brown Sandwich Bag.

That's going to add only 3 -to- 5 more mpg's for you.

33 mpg's for a 4-cylinder hi-revving plant is within median levels.

 

30 mpg for a 650 is real low Rick, I had my 1100 on a trip last weekend and got 43 mpg, mostly highway miles. I'll get 37 or so on average riding.

 

+1
That’s how I have always responded to the question when asked what my MPG is.
Many people assume a motorcycle gets outstanding MPG. (Maybe they are confusing with moped)

Some of the posted MPG #s I see are wildly different.
I wonder how much driving habit’s contribute to MPGs?
Above 50 MPG is hard to believe. Maybe if you shift up fast, stay below 3K RPM and drive down hill with the wind at your back – both ways

 

mine's around 35mpg on the highway at 65-75 mph. I can make it use fuel much faster by hammering on the throttle but nice steady cruising will keep the mileage up.

 

Thanks so much fellas.
I have pulled the plugs and they look good. The air filter is brand new. I changed oil too.
I will check the breather and maybe do a carb clean. Can a guy spry carb cleaner into the intake and maybe that would be a quick fix before winter???

 

Oh also. She doesn't travel more than 65-70 mph (which I think is around 105km/h) on the highway. I took it for a couple rides and it revs around 5 and a half on the tach.

 

benchpress
don't spray no carb cleaner into the intake. It can ruin all the rubber parts.

 

Thanks and good call. That makes alot of sense.
I figure I might just have to run it the way it is until winter and then do the entire thing.

 

just a comparison.

my 94 suzuki 1400 vtwin gets 45 mpg. 8k miles
my 94 ninja 600 i had last year got 57 mpg. 12k miles
my 86 V65 magna (1100cc) got 42 mpg. 35k miles.
my 82 V65 magna got 47 mpg. 5k miles.
my 81 maxim 650 got 35 mpg. 33k miles. while my 82 maxim bought brand new in 84 got 60 mpg. the whole entire 45k miles i owned that bike. and the only work that bike ever had done to it was 2 carb syncs, regular oil changes, brakes, and tires.

 

Interesting about the difference in an 81 and and 82 xj650.
Wonder why that is?

 

the 82 was brand spanking new. only maintainance done was 2 carb syncs.


the 81 was 29 years old with worn piston rings and engine blow bye. the compression wasn't quite as high as one i seen on a motor that was rebuilt. 140 compared to his 165. i didn't think to ask what he got for mileage as i was only curious as to his compression.