Help understanding fuel valve

[Joe Garfield]

My bike seems to have a 3 position fuel valve, labeled: pri, run, and res. Is there no fuel shutoff on my bike? It's an 82 650L and I'm ready to put the bike up and start taking things apart.

Thanks.

[tkent02]

PRI is always on, drawing from the bottom of the tank, like reserve.

RUN or ON is the normal position, the fuel only flows when the engine is operating thanks to the vacuum mechanism. Draws fuel from a couple inches above the bottom of the tank.

RES is the same as RUN or ON, shuts off when the engine is stopped, but it draws fuel from the bottom of the tank.

Leave it in the ON position, it shuts off when parked. Use reserve when you run out of gas, should go about 40 miles or so.

PRI should only be used when the bike has been sitting a long time, or when the carbs have been drained to refill the float bowls, about 15 seconds, then back to ON.
Never leave it in PRI.

[Joe Garfield]

Ok, thanks for the info. This leads to two more questions:

1) What is the recommended/cleanest procedure for draining the fuel tank (other than running the engine)?

2) When the bike has been sitting, it starts pretty hard and any touch of the throttle makes it quit, like it's overly rich. There's some blue smoke when starting cold. Is it possible the engine is somehow demanding/drawing fuel from a leak or something? I was hoping I could turn off the fuel valve and see if this continued.

[tkent02]

Ok, thanks for the info. This leads to two more questions:

1) What is the recommended/cleanest procedure for draining the fuel tank (other than running the engine)?

Attach a fuel line from the petcock outlet, run it down into a gasoline container. Put the petcock on PRI, fuel should flow until the tank is empty. Use a long enough hose that the end is submerged in the container, once the line is full you can test the other functions, if you go to ON or RES, fuel should stop flowing completely. The siphon effect of the full line will provide a better test of the petcock's ability to shut off than just running an open hose.

2) When the bike has been sitting, it starts pretty hard and any touch of the throttle makes it quit, like it's overly rich. There's some blue smoke when starting cold. Is it possible the engine is somehow demanding/drawing fuel from a leak or something? I was hoping I could turn off the fuel valve and see if this continued.

Starting hard when sitting can be a combination of factors, carbs needing cleaning, valves needing adjustment are just a few.
If you are using the choke to start the engine, when you touch the throttle the choke is bypassed, the engine goes lean and will falter until you close the throttle. This happens less and less as the engine warms up.

Blue smoke when cold is a likely sign of poor valve stem seals, no big deal, not worth fixing unless there are other problems as well.

[Joe Garfield]

Thank you, Sir.

[1_v8_merc]

Hey my 82 GS650-G has problems holding Idle, i always have to run the bike for 15 minutes with the choke half-way, then I have to like fiddle around between the Throttle and Choke in order to get it to hold Idle WITHOUT the choke on.
(ex: I must slide the choke enough to where the RPM's sit at around 2 or 3k for 15 minutes. Then as i slowly turn the choke OFF, the bike just keeps trying to die on me! So I give it some throttle and pop the choke back up again, causing the RPM's to go up again. Then i slowly lower the choke OFF again.......and it's like I KEEP having to play this stupid game just to get the bike to hold Idle WITHOUT the choke being on!)

I checked the gas tank, there's quite alittle bit of rust in there, and chunks/flakes too.


But the Idle problem, does that sound like my Main(idle) jet is clogged?

Because im about to tear down the carbs, hoping that's what the problem is.

[tkent02]

Hey my 82 GS650-G has problems holding Idle, i always have to run the bike for 15 minutes with the choke half-way, then I have to like fiddle around between the Throttle and Choke in order to get it to hold Idle WITHOUT the choke on.
(ex: I must slide the choke enough to where the RPM's sit at around 2 or 3k for 15 minutes. Then as i slowly turn the choke OFF, the bike just keeps trying to die on me! So I give it some throttle and pop the choke back up again, causing the RPM's to go up again. Then i slowly lower the choke OFF again.......and it's like I KEEP having to play this stupid game just to get the bike to hold Idle WITHOUT the choke being on!)

I checked the gas tank, there's quite alittle bit of rust in there, and chunks/flakes too.


But the Idle problem, does that sound like my Main(idle) jet is clogged?

Because im about to tear down the carbs, hoping that's what the problem is.

The main jet has NOTHING to do with idle.
Clean your carbs.

[1_v8_merc]

The main jet has NOTHING to do with idle.
Clean your carbs.

That's weird i thought i heard someone refer to the main jet as the idle jet........hmmm oh well.

[tkent02]

That's weird i thought i heard someone refer to the main jet as the idle jet........hmmm oh well.

Two separate jets.
Two separate circuits.
Take it apart and see how it works.
If the tank has rust particles, the carbs are probably partially clogged in a lot of different places.

[1_v8_merc]

Two separate jets.
Two separate circuits.
Take it apart and see how it works.
If the tank has rust particles, the carbs are probably partially clogged in a lot of different places.

Thanks for clearing it up man!

[TheRealFatShady]

Not sure if it's the same as your bike, but I have an 82 1100L and it does indeed have an 'off' position. It's at the very top. I didn't see it at first and only had three positions; I found that odd until I looked a little closer.