GearJammer

Yep, the 450 is vacuum acuated, the 250 is gravity feed. I can't find a delete option for my previous post in this thread where what I posted is INCORRECT.

On the 450, pointing UP is "On", pointing DOWN is "Reserve". My Harley is the reverse of this and it gets to be an un-thinking thing......get on the bike, flip the petcock the right way and go......One thing to keep in mind about vacuum acuated petcocks is that if the vacuum portion fails, it can become a gravity feed, which is why I stay in the habit of turning the petcock "Off" everytime I shut down the bike. Spaced it once on the Triumph (gravity feed) and won't be likely to do THAT again, LMAO!.......gas filled up the float bowl, trashed the rubber on the air filter and the fuel level spilled into the crankcase! Was late for a run and discovered this when going to fire-up the bike. Put a new air filter on and went for it. Clutch started slipping, which is when I realized that oil had gotten into the crankcase (shared primary) so had to do an impromptu oil change in a Checker's parking lot........Got home and changed the oil again next day......whole lotta "fun"........NOT!

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel

twitch

I have an even dumber petcock question: how does it actually work? I'm always curious about the workings of things and I haven't been able to imagine how the petcock provides a reserve supply of fuel. I'm sure it's incredibly simple and that my tiny brain just can't picture it without help. I doubt that there is a separate "reserve" section inside the tank (there is only one connection to the petcock). So can anyone explain to me how that little key prevents you from draining the entire tank unless it's set to Reserve?

And dumber still--if you have been running on reserve for a few miles, you don't have to leave the petcock on Reserve when you are filling up to replenish the reserve...do you???

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2008 Rebel 250 - 11,500 miles

People are more violently opposed to fur than leather because it's safer to harass rich women than motorcycle gangs. -- Alexei Sayle

Guba

There isn't a partition that seperates the reserve from the main. It's all one tank. When on "main", the fuel pick up tube is elevated an inch or two from the bottom of the tank. When switched to "reserve" the petcock gets the fuel from the bottom of the tank directly. In Ohio our gasoline has alcohol in it. Alcohol likes to attract moisture. I routinely switch to reserve to eliminate any condensation build up.

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Some days beer tastes good...other days beer tastes better!

'07 Rebel 250 26,000 miles

GearJammer

If this link works, it might help you to picture it......the pick-up tube goes up inside the gas tank and the petcock is threaded in place to the bottom of the tank. The pick-up tube is open at the top and has another hole down near the bottom of it. The pick-up tube can be several inches long. When in the "On" position, fuel flows into the TOP of the tube, while on "Reserve", access to the lower pick-up tube hole opens up and allows fuel flow from near the bottom of the tank........The available fuel between top & bottom holes is your Reserve fuel capacity......

1985 Honda CMX250C REBEL OEM Parts, 1985 Honda CMX250C REBEL OEM Motorcycle Parts - BikeBandit.com

Edit: The link takes you to the entire list of parts schematics and starts with the Air Cleaner. Just scroll down thru the schematics and click on "Fuel Tank" for an exploded view in the window below that.....

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel

jax

The 450 petcock is a vacuum petcock. The engine has to be turning over for the fuel to flow.

Ride safe

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GearJammer

Please don't be offended, jax, because I'm not trying to argue with ya, but vacuum petcocks can fail and not stop the flow of fuel..........

Welcome to the XS-650 Garage USA - Vacuum Petcock Problem Solved

dr650/yamaha petcock - ThumperTalk

From the thread in the 2nd link:

"Does anyone know of a cheap replacement petcock with a vacuum shut-off. I had a vacuum petcock failure and a float valve failure. I ended up with a cylinder full of gas. I forget to turn off a manual valve and I like the vacuum shut-off (if it works) for a redundancy to the float valve."

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel

mountainclimber

My '87 450 has an arrow on the switch pointing to on, off, pri. the exact opposite of the manual. Two times out of gas, I'm going down for on, up for reserve. We'll see what happens. More to come. Stay tuned. SAME REBEL STATION, SAME REBEL CHANNEL! (L0L)Not necessarily the same time.

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GearJammer

LMAO!!!!!! It's been raining here, otherwise I would have double-checked by looking at the bike. Checked the manual and changed my first reply, but after what you've just said about it being opposite of the manual, maybe I was right the first time........DOH!

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel

PhilipJ

So I finally checked my 2009 Owner's Manual AND looked at the petcock ... BOTH indicate that the fuel is ON when the pointer (knife edge) is pointing up (i.e., the handle is pointing down); OFF is horizontal; and RESERVE is with the pointer pointing down (the handle is pointing up).

Maybe the confusion is over the meaning of UP ... is it possible some of you are thinking the handle (the tab you actually twist with) should be up (12 o'clock) for fuel? My manual shows a picture in which FUEL ON is when the handle is at 6 o'clock, or in other words when the knife edge is at 12 o'clock.

A number of us are amused by this thread but there's a serious side - if someone rides thinking they're on ON when they're actually on RESERVE, and run out of gas, they'll have REALLY run out of gas ...

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GearJammer

Excellent catch, PhillipJ!......I believe you're right in that some of us were thinking about the lever and some were thinking about the arrow/pointer, which explains where the confusion probably came in.........and you're also right about running out of gas not being any fun.

Ran out of gas twice, each time on new to me bikes.......2nd time wasn't so bad. Just had to turn the bike around and push it thru the intersection to a gas station on the other side. First time ? Total drag.......had to push the bike a couple miles.......*whew*.........

Again.......excellent catch!

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel