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Petcock reserve issue.

birdland

Veteran Member
Joined
Oct 3, 2020
Total Posts
578
Total likes
41
Location
Osoyoos B.C. Canada
First time running over 90 miles on a tank and the reserve tried to kick in. Must be a blocked pipe. It lost power and started to hesitate - I had already selected reserve but when the fuel got down below main level it would barely run. I managed to limp to my regular gas station.

Filled up it ran like a dream.

I cleaned the petcock screens a year ago. Probably time for a replacement petcock. Maybe an in-line filter as well.

These are mileage numbers.

12L = 3.2 us gal
12L = 2.6 imperial gallons

Trip:156.0 kilometers
Fuel:12.00 liters
L/100km:7.692
L/100km = liters per 100 kilometers

Equivalent
Fuel Consumption Ratings
MPG US = 30.578
MPG Imp = 36.723
km/L = 13.000
L/100km = 7.692

Latest plug (about 15 miles on it) pic.

38358d345fee8cdffb405373f0ebf93e.jpg
 
Please explain "reserve tried to kick in".

Are you saying it took 12L/3.2 US Gal to fill up when you got to the gas station? I believe your fuel capacity is 3.6 US gallons leaving .4 gallons in the tank. Should be plenty to run on it seems.

You could disconnect the fuel line(s), route them into a suitable container, then turn the petcock on. When fuel stops flowing turn the petcock to reserve and observe the flow. If it does not resume flowing normally you have a restriction in the reserve circuit.
 
I had a non-functioning reserve, even with a clean bowl screen. Turns out the reserve passage in the petcock was stopped up with crud. I cleaned the petcock out and it worked fine after that.
 
The owner's manual says it is actually 11.7L, so you milked it a little higher. Only 31mpg US seems rather low; I think mine's low at 42mpg US, and my overall average over a bit more than 12000 miles is about 51. Brake stuck on?
But yes, I think your short petcock tube is blocked - it is near the bottom of the tank. That, or you have water built up in the tank.
 
The owner's manual says it is actually 11.7L, so you milked it a little higher. Only 31mpg US seems rather low; I think mine's low at 42mpg US, and my overall average over a bit more than 12000 miles is about 51. Brake stuck on?

But yes, I think your short petcock tube is blocked - it is near the bottom of the tank. That, or you have water built up in the tank.


It rolls well - without effort - both brakes were serviced a few months ago. I'm thinking the poor mileage has to do with the saddle bags and windshield. Also I run almost exclusively in town and rarely out of second gear. On the highway I keep 4 - 5k rpm. I've found a set of exhaust pipes that are in excellent condition - I plan to attack the mileage issue when I get them in the stable.
 
I have a small shield, but no bags on the sides, but don't spend a lot of miles riding at low speeds around town, so that is maybe the difference. Mileage is certainly less when I ride around town a lot.
 
I haven't checked mileage on many bikes over the years, but a good example of the fair amount of difference between running in lower gears and/or high performance riding vs highway miles was pretty significant on my first CBX. On the road during our 1980 trip to Atlanta running steady interstate speeds it got 40 mpg, but rat racing around town it only got 25 to 28.
 
I went with the 'put air through the line' method of clearing this issue.

Petcock lever to off position.

Removed the fuel hose from the right side carb at the carb inlet.

Clamped closed the fuel line from the petcock to the left side carb

Opened the filler cap

Opened petcock to reserve

Applied pressurized air to the right side carb fuel line (20 psi)

Got a thump out of the tank when the air cleared the line.

Gave it a couple of shots


Buttoned everything up. Seems to be working fine when reserve selected. I ran the tank low and the reserve works fine.
 
I went with the 'put air through the line' method of clearing this issue.

Petcock lever to off position.

Removed the fuel hose from the right side carb at the carb inlet.

Clamped closed the fuel line from the petcock to the left side carb

Opened the filler cap

Opened petcock to reserve

Applied pressurized air to the right side carb fuel line (20 psi)

Got a thump out of the tank when the air cleared the line.

Gave it a couple of shots


Buttoned everything up. Seems to be working fine when reserve selected. I ran the tank low and the reserve works fine.

The thump tells me there was something clogging the reserve exit port inside the tank, so it will probably happen again
 
Same thought. Petcock comes out in a while here to drain tank completely. Last time this was done was around a year ago.

Must be some gunk in the bottom of the tank then, sounds like a good flush is in order once the petcock is off.
 
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