silly petcock question...

Hello BMW world!

I am new to this site, and kin dof new to owning a bmw (6 months now).

ANyhow, i have a '93 R100 GSPD and was wondering which way the petcocks on the fuel tank indicate what setting they are on? I have never run out of gas as the tank is large as heck! but i am going cross country soon and would really like straiten out once and for all just where the "on" is and where "reserve" is. I dont know if the long ind of the lever is to indicate the losition or whether there is a small arrow on the center of the knob that i should be looking at...any thought?

thanks!

Congrats on the purchase. If my memory serves me right, pointing down is on, middle is off and pointing up is reserve.

A website that should help visually with the positions:

http://w6rec.com/duane/bmw/petcock/index.htm

On my petcocks, the straightdown kind (there are also petcocks available with a 90 degree angle, but I think the lever positions are identical. I think, double check that with a call to a dealer):

- Down (18:00) is on [Fuel flowing].
- Up (12:00) is Reserve [mental note "Up means I need to 'fill her UP' on reserve"]
- Sideways (09:00 or 03:00) is off [no fuel flow]

(* All this assumes, of course that you have a left hand petcock on the left side and a right hand petcock on the right side.)

I always turn my fuel off web stopped, short or long term just in case a float needle sticks and the bowl fills up, gas will run out onto your boot and the ground. Not good.

Also, I only ride with ride petcock on, leaving the left off. There is a cross-over tube so that both carbs get fuel with either of the petcocks open (on). The thought is that if I feel a stumble when I know I am low on fuel, I can reach down with my left (non-throttle) hand and flip the left petcock up (reserve), forcing me to make a mental note that I need fuel. Search the forum, you'll find that different riders have different reasoning and styles with respect to petcock positions.

The "long end of the lever" indicates the position of the petcock. As previously mentioned down is on, up is reserve. Your bike is newer than mine, but I don't think that changed.

Check with your dealer--you can still get an owners manual for your bike.

Silly Petcock Question . . .

I have an R100RT and the petcock on the right side is oriented so the outflow goes toward the carb. On the left side, the petcock outflow goes forward and the fuel hose must do a 180 to go back to the carb. Are there petcocks that with oriented outflows?
Campbell
R60/5, R75/5, R90/6 and R100RT (presently)

PO must have put a right side fuel tap on the left side. Yes, there are L and R fuel taps

rocketman said:

don't think thats ever been a problem even with the big value 100's, never on mine anyway, but I generally open both anyway, that way I'm going around 200 miles before reserve, then go to reserve on each side seperately. Even running one side only full out, never had a fuel starvation problem. but as said by others it pretty much a personal choice, with everything running right and no clogs in the lines or filters/screens, one side all that's really required, the rest is just a personal methodogy, no one method better or worse.

RM

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+1 on Rocketman's take. I also ride with left off, right down (open). When is sputters (around 210) I flip the left side to reserve without taking my hand off the throttle. I commute 40+ mile to work on the DC Capitol Beltway and other highways, so my high speed may not be your high speed (75-80 max), but I've had no fuel starvation issues. Dual plugged, Bing 40mm R100 usually keep it at 3800-4000 and cruise at 70mph.

Question on reserves: a fellow airhead recommended cutting the feeder tubes down by 3/4" each on the petcock. This to get more mileage out of your regular feeds and still have (in his words) plenty of reserve. Call me old fashioned but I'll stick with the factory lengths even if I do live in a quasi-city setting where fuel is readily available. Any thoughts? Has anyone done this? Regrets?

Question on my tank size. My '83 has the large tank (re: first introduced with the R90S I think). I read an article that later models the capacity was actually reduced on the right side to allow for some frame mounted hardware (electronic ignition maybe? The end result was that the right side reserve is less than the left side. I think the earlier tanks held 6.3 gallons, so this would be less. I haven't emptied the tank to check mine, but there are plenty of things under my tank that it would make some sense.

Guess if I get really curious, I could empty the tank and look at the symmetry underneath. Then put a gallon in and ride up to fill it.

AnnapolisAirhead said:

Question on my tank size. My '83 has the large tank (re: first introduced with the R90S I think). I read an article that later models the capacity was actually reduced on the right side to allow for some frame mounted hardware (electronic ignition maybe? The end result was that the right side reserve is less than the left side. I think the earlier tanks held 6.3 gallons, so this would be less. I haven't emptied the tank to check mine, but there are plenty of things under my tank that it would make some sense.

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Even on the R90S the two sides are not symmetrical, and the right side has a smaller reserve volume. This is because BMW put some of the electrics along the right side of the frame backbone.

In 1985, the US-bound bikes received a new evaporative emmissions system that included two large solenoids and some plumbing that was all hidden under the tank on the right side, and they correspondingly further reduced the right side reserve (as well as the tank's overall capacity).

DarrylRi said:

Even on the R90S the two sides are not symmetrical, and the right side has a smaller reserve volume. This is because BMW put some of the electrics along the right side of the frame backbone.

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Oh good, so I wasn't going crazy.

DarrylRi said:

In 1985, the US-bound bikes received a new evaporative emmissions system that included two large solenoids and some plumbing that was all hidden under the tank on the right side, and they correspondingly further reduced the right side reserve (as well as the tank's overall capacity).

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Ok, my 1983 had the emissions gear too but those solenoids you speak of were (I bought the emissions removal kit from Bob's) both inside the airbox just under the rectangular air filter. The top of the airbox has a black plastic, flat cover with two forward facing air tubes (think poor man's ram air), so maybe they also accounted for that.

My frame tube is packed full of electrics, some stock, some added later. It has electronic ignition (stock), dual plugged coils and a Dyna ignition booster that I think was added to ease starting because of the dual plugging--but I can't confirm that.

Thanks for the info.

AnnapolisAirhead said:

Ok, my 1983 had the emissions gear too but those solenoids you speak of were (I bought the emissions removal kit from Bob's) both inside the airbox just under the rectangular air filter. The top of the airbox has a black plastic, flat cover with two forward facing air tubes (think poor man's ram air), so maybe they also accounted for that.

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You're talking about the air injection system that puts fresh air into the exhaust tract in the head. In '85, BMW added a system that changes the gas tank vent routing when the bike is turned off, in order to pass the California "Shed Test"*.

The Shed Test is a test to ensure that the vehicle doesn't give off hydrocarbons while it's parked. This is the same reason we have those inconvenient rubber snorkels on the gas station hoses here. What BMW did was to change the tank vent routing so it first went to the crankcase and then to the airbox when the key was off; when on, the vent went directly to the airbox. The (in)famous charcoal cannisters on the newer bikes are another approach to passing this test.

*It's called the Shed Test because the basic idea is to run the vehicle until it's warm, about 20 minutes, turn it off, roll it into a sealed room (the shed), wait 24 hours and then measure the hydrocarbons in the air.

I've had to google this a few times, but SHED stands for Sealed Housing for Evaporative Determinations. This page shows a company's "shed" with a bike inside.

http://www.webberemi.com/Brochures/SHEDs Brochure.pdf

Amazing. I had no idea it was an acronym. I think I still like my version better.

DarrylRi said:

Amazing. I had no idea it was an acronym. I think I still like my version better.

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A literal and figurative acronym...what California and the "lovely" CARB won't think of next!!