Petcocks on or off after a ride

[pepper0315]

I have a Harley lover telling me that I should tun the petcocks to the off position after parkink the bike. Is this necessary? I thought if they were in the on position, there had to be vacuum to draw the fuel....

Thanks

Andre

[Dragonrider]

If the petcocks are working correctly (or the octopus on a special) then when there is no engine vacuum they shut off.

Petcock stuff is like tires and oil. Ask 2 guys and you'll get 10 vehement opinions.

I like my vacuum petcocks. I leave 'em on and let them do the work.

[2fast]

As Dan said, the vacuum control generally works. If it fails and fuel is on when the bike is off, then one or more float valves in the carbs would have to leak in order for a problem to occur. If you do have both problems occur at the same time, it is possible for gas to drain into a cylinder and prevent compression when the engine is turned over to start. This condition is called hydrolock, and may result in a bent rod, or other problem. Fairly rare, but it can happen. For this reason, you might consider checking you oil sight glass before starting the bike (with the bike level) to be sure there is some air space in the engine.

[xj11john]

gas in the oil

You may want to check you oil for gas-as 2fast alluded to your oil level could go up from gas in your crank case,
a good way to check your oil for gas in it would be; to first step to a safe area, take a stick or something skinny enough to dip into your crankcase, and then take a lighter and put the flame to the oil on the stick- if it burns-flames up, you have gas in your oil.

"If" all your componets are working properly-(your petcocks, your vacuum diaphram-octopus, and your needles and seats) then the gas will not get into your oil, but just one of these fail and then you will have this problem.

In my case My xj had all three probs, 1.) one of my petcocks were leaking, the rubber gasket had a nick in one of the holes that allow fuel to flow 2.) my needles were worn and leaking past the seats, also the seats had bad o-rings. and 3.) the octopus had a bad vacuum diaphram.

Any way now I just shut off the petcocks, I'd rather be safe than sorry. (also a side note-I eliminated the vaccum-octopus, since I have heard some suppliers send the wrong diaphram)

so that's my $ .02

[GNEPIG]

.. turn em off .. cheap insurance, besides its just easer

[prometheus578]

Dear Abby

ASK MR. HARLEY:

Dear Mr. Harley,
I have a 79 XS1100F, and my petcocks say ON, RESERVE, and PRI (prime). Which one do you recommend for the OFF position.
I know you Harley Guys are the last word concerning technology and all matters mechanical. Your opinion and good favor means the world to me.
Hugs and Kisses,
KURT

[84xj1100]

For what it's worth - as a chief instructor with the MSC, part of our curriculum for the motorcycle course is to turn petcocks off. There are a number of reasons for this;

First, in the event of a problem with the needles/floats so fuel doesn't make its way into unwanted areas and

Second, so that the rider is familiar with the location of the valve in the event they run out of fuel they can reach down without looking and switch to reserve, and

Finally, even if the valve doesn't have an "off" selection the valve is turned from "on" to "res" then back to "on" again in order to ensure the student is familiar but also to ensure that if reserve is required that when the valve is eventully turned that it hasn't dried up/stuck and torn from lack of use.

Does that make any sense??

[pepper0315]

All of these replies make perfect sence to me.
Thanks so much for giving me some different opinions.
It would seem as though turning them off may be the smartest thing to do. And since it rains in Alberta almost every day, I won't have to worry about wearing them out will I.......

Andre

[xj11john]

unless you learn the art of using a rain suite.

I agree with you, I think it is much better to take the safest route

with shutting them off, it seems worth the extra effort.

[beechfront]

i don't like the idea of shutting them off. i replaced the vacuum diaphragm (octopus) on mine for two reasons:

1 - i don't want to wear out the fuel valve

2 - mostly i hate the embarassment when i forget to turn the petcocks back on and run out of fuel 1/2 mile down the road.

[dmac82]

I've been wondering about the petcocks myself. The PO said to never touch em, just leave them in the Res position and watch my gauge. "they are a pain in the ass to fix if you mess with em" so I havn't, but sooner or later I will probably run out of gas and wish I had!

I saw rebuild kits online when I ordered an air filter and a couple of oil filters, any opinions out there?

[prometheus578]

Your PO is a fool.
I mean, really.... he owned an 1100 and got rid of it. What else is there to say about the guy?
Fuel gauge?
"HHmmm... it's almost on "E". Do I have a gallon left, or just a pint?"
On the highway, could be the difference between leisurely finding a gas station in 30 miles, or running out of gas in 3.7 miles.
Fill the tank, set the petcock to run and then "zero" the trip meter. Run the bike till it starts burpin' and dying. Swing the petcock to RES. or PRI and check the trip meter. If it shows, say, 135 miles, divide by 4. Ok.... that's 33.7 miles per gallon. With a 5 gal tank, that leaves you with one gal left; 33.7 miles (plus a little) to search for fuel.
(Figures from a '79 F model... 5.3 gal tank.)
Takes the guesswork out of how much you have left.
If you still don't like using the petcocks... just do the above mentioned a few times till you get a good average MPG. Then, if you want to leave them on RUN, go ahead... just watch your mileage and fuel when needed.
Be advised... highway flyin' will cut your miles per gallon drastically and you'd need new figures to be accurate.
Yes, petcocks are a pain to fix. Take out those two screws, pull the spring-ring and the lever thingie out and replace the rubber disk inside. Took me five minutes once to do both of them. (tank on the bike and empty)

[Bigfoot]

I just fixed both of mine and the octopus with a repair kit I ordered off of ebay. Very easy to do and the diaphram seemed to fit just fine.

[Dragonrider]

Bigfoot...check that the octopus is ACTUALLY cutting off the gas. One of the brands of rebuild kits, the diaphram is fine but the valve piece is too short, and even with no vacuum the octopus will still let gas flow (was gonna say "pass gas" but...)

Anyway, make sure it's working. New octopus (Yammi part) is still available if you need one.

[Pat Kelly]

Originally posted by prometheus578

Fuel gauge?
"HHmmm... it's almost on "E". Do I have a gallon left, or just a pint?"
On the highway, could be the difference between leisurely finding a gas station in 30 miles, or running out of gas in 3.7 miles.

Takes the guesswork out of how much you have left.
If you still don't like using the petcocks... just do the above mentioned a few times till you get a good average MPG. Then, if you want to leave them on RUN, go ahead... just watch your mileage and fuel when needed.
Be advised... highway flyin' will cut your miles per gallon drastically and you'd need new figures to be accurate.

In addition, be aware of if it's windy. I was heading from San Diego to Phoenix. I knew my bike would go 120 miles before having to switch to reserve. At the 80 mile mark the bike sputtered and I had to switch to reserve. I stopped at the next rest area. When I got off the bike I realized I'd been riding into a 30-40 mph headwind. Fortunately the reserve got me to the next fuelstop (which I normally would have passed for the gas station after that one, I would have been stranded).
This particular bike, Honda Hawk, had no fuel gauge.