petcock question

[ron bayless]

On my 83 850, I had to change from run to reserve at 67 miles. Then i could run the rest of the gas out. The petcock doesnt leak.Why was that? Also I guess i should take it apart but dont know what might be wrong with it.Do the rebuild kits work?

[tkent02]

How far did the rest of the tank go?

[ron bayless]

I filled it up after about 2 more gallons, didnt want to run out.

[tkent02]

What Im getting at is what proportion of your tank is before the reserve?

Sounds like not much of it?

[ron bayless]

What Im getting at is what proportion of your tank is before the reserve?

Sounds like not much of it?

Oh, the tank is 5.8.I used 1.8 before I paniced and filled back up.

[tkent02]

Four gallons left. Usually about 1 gallon or 1.5. Sounds like the wrong petcock, one with way too long pipe inside. Maybe someone put in a longer pipe. Really strange.

Take it out and see what's inside.

[ron bayless]

Four gallons left. Usually about 1 gallon or 1.5. Sounds like the wrong petcock, one with way too long pipe inside. Maybe someone put in a longer pipe. Really strange.

Take it out and see what's inside.

You might be very correct.I dont know about the 83 year.I am used to a petcock having a small vacuum tube from it to a vent between number 1 and 2 carbs.This one doesn have that.perhaps its the right one, I do not know.I have a manual but have not had time to look at it.

[tkent02]

All of the GSes came with vacuum petcocks, '83 850 included. Someone swapped something. The vacuum port is on top of the #2 carb in front, no? Is that port blocked off?

[ron bayless]

All of the GSes came with vacuum petcocks, '83 850 included. Someone swapped something. The vacuum port is on top of the #2 carb in front, no? Is that port blocked off?

dont know, but will find out.Its too cold here.I will have to wait till it warms up later this week.42 degrees, brrr.This is endless summer territory.

[Wingsconsin]

I think this is what I know....

If my understanding is correct then the vacuum portion of your petcock may be malfunctioning..

The way I beleive these vacuum petcocks work on the GS bikes is this -- The PRIme section requires NO vacuum to operate as the REServe also requires NO Vacuum to operate..

ONLY the RUN requires vacuum to operate (and when you shut the bike off the vacuumis gone and the petcock closes to avoid leaks).

So IF the petcock loses vacuum while in the RUN position it will act as if the bike is low on fuel and you need to switch to REServe. But there is really plenty of fuel left --

Therfore - IF my assumptions are correct about the operation of the peetcock then you may need to rebuild the petcock or at least check its operation as well as the vacuum lines for leaks or pinches.

IF I am wrong...somebody please explain it to me....

[tkent02]

Reserve is just like ON, it requires vacuum to operate. The difference is it will use all the fuel to the bottom of the tank. PRI is just like reserve, but requires no vacuum on most petcocks.

[ron bayless]

Reserve is just like ON, it requires vacuum to operate. The difference is it will use all the fuel to the bottom of the tank. PRI is just like reserve, but requires no vacuum on most petcocks.

I think you have probably identified my problem.Sounds like a messed up petcock, or altered one, or plugged vaccum port, or all the above.Getting down to 20 degrees, 30 mph wind.Will have to wait a while.I appreciate your help.