83 XVZ1200 Fuel Consumption

[larrydr]

I fueled up after a short ride about 20 minutes long , and went for another short spin ...I could not believe the amount of fuel bike is using .....At the best I am doing 15 miles per gallon and the 3rd try it used a half gallon on a 6 mile ride ...I decided to take a look for the easy little things that cold be wrong ..I have no fuel leaks anywhere , air filter is new ...I was not driving it hard at the most 65 miles per hour will low rpm shifts  , with new plugs and a fuel additive .. ..I will drain the fuel tank and refill with fresh fuel and if this the mileage this bike does it is going to be a parts bike ....I have not checked camshaft timing  , but at 85000 miles is that something this engine could need .... I have repairing bikes and engines since 1964 ...I have been riding all sorts of bikes many of which were running 35 to 45 miles per gallon ...

Edited May 4, 2022 by larrydr

[Freebird]

I would wonder it it is running on all 4 cylinders.  They run amazingly well on 3 but mileage will suffer greatly. 

[Marcarl]

If you numbers are correct I would suspect that it is running on 3 cyl with the one cylinder sending all it's fuel down the overflow tube. What I would suggest it to start it and let it run in place for 20 to 30 minutes to see if there is any sign of leakage anywhere. The last time I had mileage that bad was when the fuel line from the tank to the pump got cut by the frame squeezing the line between it and the swing arm. Boy! did it leak!

[larrydr]

51 minutes ago, Freebird said:

I would wonder it it is running on all 4 cylinders.  They run amazingly well on 3 but mileage will suffer greatly. 

I thought it might be cylinders not running ..It has plenty of power ...I cleaned the carburetor chambers & slides because they were badly scratched ...To me it seems like a carburetor issue ...Seriously considering a single carburetor conversion 

[larrydr]

Just now, Marcarl said:

If you numbers are correct I would suspect that it is running on 3 cyl with the one cylinder sending all it's fuel down the overflow tube. What I would suggest it to start it and let it run in place for 20 to 30 minutes to see if there is any sign of leakage anywhere. The last time I had mileage that bad was when the fuel line from the tank to the pump got cut by the frame squeezing the line between it and the swing arm. Boy! did it leak!

The overflow tube on one carburetor was pushing fuel out , gave the carburetor a little tap and it stopped , then added some sea foam .. The fuel spill quit , I then  replaced all fuel lines and installed brass fittings at all curves or corners the fuel lines need to make ...Only to avoid any line being pinched ... The carburetor slides and their chambers were a bad mess .... If I do not do a single carburetor conversion , I do know where there is set of carburetors that are available .

[luvmy40]

I'd lay short odds you only hitting on 3 cylinders. My 83 was only running on 3, sometimes 2 when I got her and she had plenty of power and sounde pretty good. I could not beleive the difference when I got all four firing.

[larrydr]

8 hours ago, luvmy40 said:

I'd lay short odds you only hitting on 3 cylinders. My 83 was only running on 3, sometimes 2 when I got her and she had plenty of power and sounde pretty good. I could not beleive the difference when I got all four firing.

The plugs have about 200 miles since new , but will replace them tomorrow ...Then I will my Oscilloscope to check for ignition through the rpm range , next I will do a carburetor balance which was done 200 miles ago ...If there is a problem I will find it ... Some of the other riders are finding a problem the 15% ethanol blend gasoline ..

[videoarizona]

There are two other things to look at:

1. The carb floats are set wrong. Yea, I know that shouldnt effect mpgs, but it does. Weird. Lean those floats. To much fuel

2. Carb diaphrams are holy! If the diaphrams have even the teeniest holes or are not supple or installed properly will ruin the mixture to the carbs. 

Suggest you think small things first. Forget plugs, etc., Unless she's not running in all 4. Easy test. Check exhaust temps just after start.