Motorcycle Reserve Fuel Switch Guide

Fuel PetcockFuel PetcockSo your cruising down the freeway and all the sudden your motorcycle starts to lose power. Its still chugging chugging chuggin along until finally you are forced to pull over and the motorcycle dies. We have ALL been there before, and the lucky ones of us know that its a simple problem of flipping the fuel tank petcock, but for the new rider it can be very confusing and intimidating.

Since most motorcycles do not have fuel gauges the kind engineers that designed our bikes decided to include a reserve fuel tank inside the main fuel tank. That way you don't have to keep opening your gas tank every time you go out to see how much fuel you have left. Basically the reserve switch for most bikes I have been on will be right below the gas tank/seat area either on the right or left hand side. It will be a little flip that usually says "On, Off, and Reserve" or something like that. This little switch is called the Fuel Petcock, the "on" position is what it should be set to when you are regularly using your motorcycle. If your motorcycle dies on you like in the above situation the first thing you should do is flip it to the Reserve position and see if that fixes things, which it will if its a fuel problem. The Off position should only be used when the motorcycle is going to be sitting unused for a very long time, like in the winter for storage.

New riders should keep in mind that the Reserve tank only carries about a gallon of gas (maybe more or less depending on the model of bike), so it should get you 20-30 miles, but any more then that and you are definitely pushing your luck! A good test to do is to strap a gas can to the back of your motorcycle or have someone follow you with a gas can in their car while you drive your motorcycle on reserve until it finally dies. That way you will know exactly how many miles you can travel before your out of luck.

Comments

It's also important to note that when you fill up remember to put the switch back in the 'On' position, otherwise the tank might not fill up the the max and then you're really screwed

It doesn't matter what position the petcock is in when you fill your motorcycle's one and only fuel tank. There is no separate "reserve tank;" there are simply two separate fuel pickups in the tank, and one (the reserve) is lower than the other (the main). Because the reserve is lower, it has access to that extra gallon or so of fuel in the bottom of the tank below the main line. You should, however, remember to switch the petcock back to main when you fill the tank, not because it makes any difference on how full you can fill the tank (it doesn't), but because if you leave the petcock in reserve position, and then run out of fuel, the tank will be truly empty and you'll have no reserve fuel on which to ride to a service station.

Hi, I understand this now, but don't know which position is which. For instance, in the photo there, is the switch set to reserve, as the lever is covering res, or on, as it's pointing towards on? Many thanks for the site, it's great.

If you are a new rider, I would recommend practicing moving the swith first while the bike is stationary. In theory, you should be able to operate the switch correctly without taking your eyes off the road while riding. Take my word for it, this is VERY important. I can't tell you how many times I've had to do that in traffic!

I'm glad I found this page. I've owned a Yamaha Fazer FZX700 for awhile now, and was always confused by its reserve switch: does "On" mean the RESERVE is on, or does it mean the regular fuel is on? Now I know! On=regular, and Res.=reserve. Makes sense, but the way it's labeled is kind of confusing (I'd include a picture if I could but I can't.)

I replaced the PC Valve on my bike in hopes that I could run my bike with the valve in the ON position. However, The bike boggs down and dies out when I have it in this position after riding for a few blocks. However, if I have it in the ON position and just let it idle the bike wont die-out.
I was told to fill it up with 91 octaine gas "the expensive stuff". It runs great in the RES position though in idle or when I am on the road. Please help.

I forgot about the reserve switch by the first time I actually ran out of gas. I pushed my bike about 2 blocks to a gas station and filled up but it still wouldn't start. I had to switch over to reserve to start the engine and then switch back.

How helpful! ok, but to throw a wrench in - My petcock shows res (reserve), on, and pri (prime). From what I can find online 'prime' is used when the motorcycle hasn't been used for quite a while. true? and having just gotten it back from the shop, I didn't check it when i left, (bad me), but when I got home I looked at it and it turns out I drove 40 miles home on PRI rather than ON. So, does anyone know where my OFF is (it doesn't rotate to the 4th quarter position) and whether it matters if I drive in PRIME or ON? I'm waiting to get the Owner's manual from the guy I bought it from, but if anyone knows before then, I'd be grateful.:) 2000 Kawasaki Vulcan 800.

Your petcock has three positions: Reserve, Prime, and On.

Prime: This is the position you would use only if your carburetor bowl is empty, and that usually only happens after the bike has been sitting unused for a long time - like over the winter. You should NOT run normally with the petcock set to Prime, because it lets gas flow to the carb freely - whether the engine is running or not. It is to be used for priming the carburetor bowl only.

On: This is the setting you should use regularly. It is enabled by a vacuum-operated diaphragm, so it only allows fuel to flow when the engine is running. When the engine isn't running, the diaphragm is closed. Therefore, no fuel will flow from the tank to the carb.

Reserve: This setting is works almost like the ON setting. It is enabled by a vacuum-operated diaphragm as well. The only difference is that it uses a different fuel pickup tube whose opening is lower in the tank, therefore it can access the last bit of available gasoline.

I was reading the comments posted about the three different setting and just want to understand when to use the PRI setting. If I am out riding I should use the ON setting, but if I finish riding for the night, should I then turn it to the PRI setting?

Always use the "on" position unless you run out of gas then use the "res" till you get to the gas station,then go back to "on". The only time you should use "prime" is in the spring when the bike has been sitting for a couple of months. Just before you start it switch to "pri" then start the bike, as soon as it is running turn the valve to "on". When you are in the "on" position, the bike has a valve that knows to close when the engine is not running so you don't have to switch anything. Older bikes have an off position but if you don't have that option don't worry about it, an keep it "on"

Some bikes have a simple pivot valve that closes the reserve fuel pickup when it is full of gas. When your fuel level drops the the valve allows gas to enter the reserve tube. The reason the bike ran for a short period is it was using the balance of the fuel in the tube after fill up. When this ran out it died forcing you to do what you should have done before, take it out of the reserve position. Now you have a reserve tank again. The shut off could be annoying but if you think about it, running out of gas with gas in the tank is better than really running out of gas on the road because the reserve was still on.

i looked at a bike yesterday and the kid that had it left it in prime position. he bought a busa so the katana hes trying to sell has been sitting in his garage. it took a while to start. i guess its ok to have it set to prime bc its been sittin for a while but i dont think i saw the OFF position. wheres the off position??????????

Does anyone know why when i ran out of fuel lastnight and put it in reserve and went to the gas station - i forgot to put it back to on.

I was driving to work today and the bike stopped. I investigated and found it was in the reserve position. Switched it to ON and I was good as gold again.

How come it didnt use the small straw for the whole tank???

Some bikes have a simple pivot valve that closes the reserve fuel pickup when it is full of gas. When your fuel level drops the the valve allows gas to enter the reserve tube. The reason the bike ran for a short period is it was using the balance of the fuel in the tube after fill up. When this ran out it died forcing you to do what you should have done before, take it out of the reserve position. Now you have a reserve tank again. The shut off could be annoying but if you think about it, running out of gas with gas in the tank is better than really running out of gas on the road because the reserve was still on.

Wow that is wierd !
What year do you have?

I've just bought a used, restored 1982 Honda 450cc and love riding it.
The former owner told me he got 170 miles to the tankful, so for the first tank, I refilled at 173 miles. 3.25 gallons
Then I got bolder, and commuting 40 miles to work, ran the bike at highway speeds to 200 miles.
I gassed up again, 3.25 gallons.

Today, I rode to work in 90 degree weather, and have some concerns about having gas in a tank setting in the sun and expanding. I am at 160 miles, and tonight, must ride 40 miles home... and will be close to 200 miles per tank again.

But after reading your comments and article above, I am concerned that my petcock reserve valve MAY be on reserve instead of "ON". I can figure out that "OFF" must be in the middle, and the longest part of the valve lever is currently pointed up to the seat.
Does this mean Res. would be straight down? How do I tell? The valve is not labled, and there is no owners manual.
There is no Honda shop near me.

Any advice? Thanks guys!

Alright, time for a confession.

I also have a Honda form the 80s.

I have not looked at the petcock valve for a long time. I just assumed that it was in the "ON" position. (I KNEW it couldn't be in OFF...)
After reading that last posting, I went out to look at my valve, to see if I could help the guy just above... and what did I find?
My value has molded in the housing "ON...OFF...Res". But instead of being set to "On", it would appear that my valve was set to "Res..."

I had always heard that the long arm of the valve handle should point to the indicator... that is, if the long handle points to "OFF"...it's Off. If the long handle points to "ON", it's on....

However, after close examination, it appear that my valve hand is an arrow, and the long handle is the 'feathers" and the head points to the setting. I confirmed this by trying to turn my valve to OFF, but found that only the head can get to that position. I had misread the valve setting all these months...

OR, somebody has attempted to play a MEAN trick on my, but switching my valve to "Reserve" while I was parked and in a store, or similarly unwatched.

How common is this, and how often do YOU check your valve?

Motorcycle Safety Foundation says FINE-C is to be checked every time you mount the cycle. That would have had the Fuel checked first, right?
Fuel
Ignition
Neutral
Engine
Cut Off

Right?

Fuel Ignition Neutral Engine Choke

Before every ride spot-checks taught during CBT (Compulsory Basic Training) are as follows:

Brakes
Oil and Levels
Lights
Tyres
Suspension

Fuel, Ignition, Neutral, Engine Cut-off, Clutch/Choke

Andrew

Andrew

Hey guys
whenever i take my bike out after a few minutes it dies, and refuses to start again. That is until i put it to reserve and then it runs, now my tank has about more than half a tank of gas in it so why would it die? ive discussed with a friend who said it might be from going up or down hills to fast, which might reduce the flow of fuel through the lines, if the tank is only half full. My bike just did it again today when i went for a ride, i put it to reserve and it was fine. I know i wont run out of gas cause i have half a tank left but why does it die and force me tp put it on reserve. its a 2007 suzuki gs 500 brand new with not even 100kms on it, all those that ive put on it myself, please help guys, thanks alot

if you have any other helpfull info please email me at morgz_420@hotmail.com

Take it easy and ride Safe

I do not want you take this the wrong way so please don't. I have read through some of the previous questions on this thread and it seems there is some confusion as to the position of the petcock valve. Your proplem appears to be very simple - you are putting the valve in the wrong position.

For most common brands of bikes the correct way to determine the position of the petcock valve is: looking at the valve position switch you will see that the pivot point is NOT in the middle. One side is longer than the other. If your switch has 3 positions they will normally be RES at the top, OFF in the middle, and ON on the bottom. The valve should turn 180 degress not fully around. You will see that the longer part of the valve CANNOT point to the OFF position. The short part is the position indicator. For normal riding the long part should be positioned to RES and the short to ON position. Remember, the SHORT part is the position. What that means is that the valve will turn clockwise for 180 degrees to change from ON to RES positions, or put another way, the top of the petcock will go towards you (when sitting on the bike) to the center and then down away from you for a half circle.

There may be some bikes with different petcock valves then described above. The simple test is to point the 3 position valve to OFF position. If for some reason only the long part of the switch points that way then that is your position indicator. If you have custom built, an exotic, or some sort of specialty bike this procedure could be different. Over 35 years of riding a variety of Japanese stock imports, this has been the method for the petcock.

I hope this helps.

UP OR DOWN HILLS TO SLOW FOR that part above LOL

I also should add that when i put 5 dollars of gas in it the other day to bring it abit above half tank or so it ran completely fine in the regular on position, could it be a problem with the fuel line or something, thanks again guys!!!!!

I stick to my theory that you have the petcock in the wrong position. When the fuel level is above a certain point (could be a third or half a tank) a valve in the tank will allow reserve fuel to flow in to the reserve line. If the tank is filled above this point the valve shuts and it will use the fuel in the reserve line untill it is gone and bike will stop. You then think you are shifting to RES but you are in fact putting into ON. The bike starts and you ride for a while again. At this point you only fill to what you think is half a tank, put the position back into RES (which does not shut off the fuel to the reserve line because it is low enough) and you "believe" you are in the ON position until it runs dry and won't start in either position. More than likely you put gas in the tank, switching between both positions trying to get her started. This gets fuel in both lines again and in few minutes the bike dies and you switch to RES (but you are really are in ON) and bike runs again.

Hi guys,

glad I found this article!

i dont think my petcock, reserve tank switch has any labels on it,

and any one tell me what the positions are for a gs500e?

i have up, right and down

Thanks
Chris

Generally the positions are

Up = On (Normal)

Right (or left) = Off

Down = Reserve

Riding with my petcock valve in the main OK position, I find my cycle begins to miss or cough about 148 miles into a full tankful.

Last time this happened, I reached down at 65 mph, and tried to rotate to the res position, but had to change my grip halfway through. I succeeded in getting it switched, but found my fingers were soaked with gas.

How common is it for a petcock valve to leak? While under way? Or was this a fluke?

Thanks so much, guys. I appreciate the benefit of your experience!

Do I have a reserve? The owners manual is very vague. Since this is the model year, there are no shop manual out there to reference.

Thanks!

I am desperately in need of the petcock lever or handle for my Garelli 50cc. I know I could purchase a new or used petcock, but all I need is the lever. Thanks for your help.

Hi All! I have a 1988 Suzuki Katana 600. My Petcock has 3 positions. Front, down and back. The problem is, that its not marked as to what goes where? I checked my manual, but nothing in there either? If I took the fairings off would it say underneath? Can anyone shed some light on this for me?

Thanks in advance everyone.

Ran out of petrol!!!!!! Bike didn't tell me to change to reserve! instead just ran dry???????

First time this has happened....anyone had similar probs? or even better a solution.

I believe the arrow should be pointing down for standard running.. Straight up for reserve... And either front or back for off...

Dagger

I just want to make it out of this life alive...

I just want to make it out of this life alive...

i have a little 125 cc pit bike, and it has been giving me trouble, im not sure which way the switch must go, coz it doesnt say on , res or prime, it just has a full cup at the top and a almost empty cup at the bottom and a dot in the middle, when i put it on the full cup, my bike is off dudring this, it just pours out petrol, when i switch it to the almost empty cup, it carries on puring petrol, but when i put it on the dot, it stops . Help?

I am having similar problems to an earlier user on this forum. My brand new bike was running just fine and now it pulls, jerks, and then dies when it goes even a mile . The problem seems to be especially bad going up hills. I thought it might be the petcock so I filled the tank with gas, tried both the ON and RES position but the problem's still there. I'm thinking the engine might be flooded and maybe I'll try a repair forum (or ask the dealer where I bought it) for more ideas but just thought I'd ask if there isn't something bleedin' obvious I'm missing...Again, the bike is brand new and have only put about 200 miles on it before this problem arose...Thanks to anyone and everyone in advance who can help...

Alec

take it on a test ride again and when it does open the gas cap. I know this is repetitive from me but it seems like it's an ongoing problem from the way the delivery company sets up the fuel lines. Sometimes if the tank gets over full you can block the "vent" hole near the cap that actually lets air in the tank for the gravity/vacuum pull of fuel to get into the carb. Another thing that has happened is actually having one of the fuel lines slightly pinched somewhere under the seat. A third is the routing.... have heard of some fuel lines getting routed to the wrong ports.

****Life's journey is not to arrive at the grave safely in a well preserved body, but, rather to skid in sideways, totally worn out, shouting "Holy Shit....What a ride!!!"****

thanks. opened the gas cap but no change. since it's under warranty, will take it back to the dealer...