Petcock

[jcknapp]

Ok so I have a stock petcock on my 1971 cb500 four. It has r
Off , on and reserve. It has 2 lines coming out and going to the carbs. I redid my carbs and disconnected the lines. Now I'm confused what line is the reserve and the main tank? Does it matter? Prob a dumb question but does anyone know? Thx

Justin

[hairygit]

They're both the same, each one feeds 2 carbs. both of the lines respond to the tap together, that is they supply fuel in the "on" or "reserve" position, and both cut off when fuel tap is off later Hondas had the single line which split off to fuel all carbs, probably cheaper to manufacture, only 1 drilling and spigot, and only 1 fuel line, so less cost to Honda  

[jcknapp]

Ok cool. My question however was the on is for the larger portion of the tank is what I'm thinking. The reserve is the other side of the tank or is it the bottom of the tank. Just wondering if I got the lines mixed up. On my on position my mpg is only 50 per tank. Then I switch to reserve. My old mpg before I put velocity stacks on and rejetted was almost 100 mpg. So I was wondering if I was running the reserve when I got 50 mpg. Thx

Justin

[hairygit]

Yes, "On" is most of the tank, and "Res" is the bottom of the tank, 100 mpg sounds like it was running dangerously lean, especially as a U.S. gallon is about 15% less than a U.K. gallon

[jcknapp]

100 per tank not miles. Haha. My mistake. So how do I know what fuel line coming out of tank is on or reserve? Left or right nipple coming down from petcock?

[hairygit]

As I said previously, they are BOTH the same, Inside the tap where it attaches to the tank there is a pipe, which supplies the main feed, once the level in the tank has fallen to the level of the pipe, you get the symptoms of running out of fuel, so when you put the tap to reserve position, it allows the remainder of the fuel to flow. The outlets of the tap are both the same, not a case of 1 for main and 1 for reserve, you need to connect both, but it makes no difference which goes to which, as they both supply fuel, except when the tap is OFF

[jcknapp]

Ok makes sense now. Thanks.

Justin