Fuel Ignition Switch

[Will]

You know some of them have on, off, and reserve. I know what reserve is, but does it matter if we leave it on the on position? In the MSF class, part of the start up procedure was the FIN-C, Fuel Ignition on, Find Neutral , Clutch and Start, or something like that. Is it important and if so why?

[Over TWO Customs]

Hmmm...

Some bikes have ON - PRIME - RES - OFF

These are your options. ON is sucking from the main tube in the tank. Some carbs pull gas based on vacuum. The more throttle the more gas they suck into the bowls. Others are strictly gravity feed from tank to carbs. Reserve pulls gas from a lower point in the tank. Prime usually is present on bikes with a fuel pump and carbs.

Good habit for carbed bikes is to turn the fuel off when you park the bike. You do not want gas to sit in the carb bowls for extended periods of time as it will cause runability issues.

[NiceGuysFinishLast]

Prime is for carbed bikes, for situations where you may have run the float bowls dry (maintenance, running out of gas, what have you).

Theoretically, on a bike in prime running condition, there is no problem with leaving the petcock on ON. However, if there are small problems like stuck floats, gas can continue to flow when you don't want it to, so it's good habit to turn the petcock to OFF after every ride, but I never did. However, Lorne, I'm surprised to hear you give patently erroneous advice. The gas that's in the float bowls will sit in the float bowls regardless of whether the petcock is turned to OFF or not at the end of the ride. Now, if I misunderstood, and you're talking about long term storage, then we're in agreement, you should turn the petcock off, but you should also either run the bike till it dies or drain the carbs manually.

[MX Tuner]

Yeah, plenty of holes in Lorne's post. With a vacuum operated petcock, the fuel only flues when the engine is running (vacuum applied to the port on the back of the petcock) when the "on" position is selected. The "prime" position is for when you've run out of gas or just had the carbs emptied for whatever reason. The prime position allows fuel to run directly to the carbs to allow them to fill up with fuel so the bike will run. Once it starts, you're supposed to turn it to the "on" position. THat way, it automatically shuts the fuel flow off to the carbs. The "off" position is for when you're removing the fuel tank or disconnecting the fuel lines. Reserve is for when the fuel level gets low enough, it lets you know you have limited fuel available. The "prime" position has little to do with whether a bike has a fuel pump or not.

The float needle and seat in a carb is not intended to permanently shut the flow of fuel off. A properly operating float needle can seep enough fuel to run out the overflow overnight. Typically they work well enough to *not* leak but its primary job is not intended for that purpose. The primary job of the float needle is to maintain the correct level of fuel inside the carb while the bike is running. It is best to shut the petcock off before parking the bike overnight or longer. If you have a vacuum operated petcock that is operating correctly, it'll shut the fuel flow to the carbs off whenever the motor quits running.

[Over TWO Customs]

I was just trying to give a brief example of what each one is for with the wife pulling me off the computer :)

Pretty much hit the nail on the head with all 3 posts combined.

[wallypiper]

My SV has a vacuum operated petcock, carburetors and a fuel pump. It does not have a manual shutoff.

[Will]

Great thanks all.

[NiceGuysFinishLast]

Oh yeah, and just to prove I payed attention in my MSF class:

Fuel, Ignition, Neutral, Engine cutoff, Clutch.

Who remembers TCLOCS?

[AdrenalineBoyz]

Oh yeah, and just to prove I payed attention in my MSF class:

Fuel, Ignition, Neutral, Engine cutoff, Clutch.

Who remembers TCLOCS?

I havent had to punch a timeclock in many years... LOL

[NiceGuysFinishLast]

I havent had to punch a timeclock in many years... LOL


That was tongue in cheek, right?

[TarzanMan]

When I had a GS500, I can remember two times I had to switch the petcock mid-ride because of running low on fuel.

Not fun.... but I was glad that I'd already practiced it in the driveway before

[NiceGuysFinishLast]

Oh yeah, if you do have a petcock with a reserve setting, be sure to practice switching it until it's second nature, when it happens at 80mph, you don't want to think, you want to react.