HOW DOES YOUR VACUUM FUEL PETCOCK WORK (and fail)?

In this video I disassemble an RZ 350 motorcycle vacuum fuel petcock and explain how it works and show the failure mode. Links to items used in my videos and more:
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Nomar Classic HD Motorcycle Tire Changer www.nomartirechanger.com/tc-c...
I use this Panasonic camera for my videos. It is a very small point-and-shoot with 30X optical zoom.
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Some of the links above are affiliate links. At zero cost to you, I may earn a small affiliate commission if you click through the link and finalize a purchase. This small amount helps me to continue to create free content for you.
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Thanks for watching!

[@oysterslurper1138]

I put a "temporary" secondary shutoff valve on my RZ, maybe a quarter century ago, still there. Now I know that I am not the only one that had a leaky RZ vacuum shutoff. Nice fix.

[@KensGarage1]

Yeah, I was using those lawn mower ones for years. But they get sticky after a while. This is a labor intensive but good fix.

[@paulwoods682]

On my 1980s Yamaha XV1000 with stubborn petcock leaks, I discoverd that the body of the petcock on the diagphram side and the square cover with 4 screws were both warped (no longer perfectly flat), so I flattened them both with fine wet/ dry sandpaper on a machined flat steel surface. Leaks gone!

[@KensGarage1]

Nice. Glad to hear that worked for you.

[@CristianDiaz-tg1pj]

Great video! My 86 Nighthawk 450 shuts off while riding. It started happening a few days ago at 60+ MPH speeds but yesterday and today it happened at lower speeds. It won’t start immediately but after a few minutes it idles just fine.

[@KensGarage1]

Glad you like the video. You think the problem you have is your vacuum petcock?

[@CristianDiaz-tg1pj]

@@KensGarage1 I’m barely getting into bike mechanic issues so I don’t know, but do you think it’s a possibility? If not, any suggestions?

[@KensGarage1]

@@CristianDiaz-tg1pj Probably not the petcock. It could be other fueling issues or electrical. Unfortunately lots of possibilities. Good luck.

[@Paulkersey5921]

We came here looking for help on a problem this is an instructional video

[@CristianDiaz-tg1pj]

@@Paulkersey5921 Yeah, sometimes strangers way smarter than me will chime in. Someone told me to give it a try. I changed the petcock for a new manual petcock from Amazon and bike runs good as new!

[@Adventureisrael_Now]

Very helpful. Thank you!

[@KensGarage1]

You are welcome!!!

[@mikebaroz]

My VLX 600 is leaking gas, I think its from the petcock itself. When I shut off the engine, the leak stops. Can it be malfunction, always "Pri", and then when the carbis are full, it just releases fuel out?

[@mikebaroz]

Well today I've looked into it, the canister fuel pipe that is located under the seat towards the carbis, was dissconected. Seems to be ok now.

[@mareksv1947]

My honda cbf500a 2007 drinks about 8l/100km. Petcock could be at blame?

[@koyval22]

Or can we change the petcock that doesn’t have a vaccum?

[@KensGarage1]

Yes, if you can find one that is form, fit, and function the same as your OEM one.

[@koyval22]

@@KensGarage1 thanks Ken! I have a bandit1200 that has a leaky vacuum. Good timing on your vid!

[@davidhoward8951]

Where can you buy a petcock that fits a 2015 DRZ Supermoto that doesn't have vacuum

[@danielgajardoroll4all960]

How can I get just the filter? Some alternative? well, i need it for zrx1200r kawasaki bike

[@KensGarage1]

Good question. You may have to find a zrx forum and pose that question. That's quite a cult bike and I would think you can find an answer somewhere out in the great www.

[@koyval22]

Nice bike. Super rare nowadays the Zrx1200. I got a bandit 1200.

[@tonalambiguity3345]

How does the petcock still work after you bypass the vacuum? Without vacuum, wouldn’t the fuel keep flowing to the carburettor and flood it?

[@KensGarage1]

The modification deletes the vacuum and turns it in to a pure mechanical petcock. It has OFF ON RESERVE. In the OFF position no fuel flows.

[@tonalambiguity3345]

@@KensGarage1 appreciate the reply. Maybe I’m not understanding something correctly but without the vacuum opening and closing the diaphragm, how does the mechanical petcock regulate the flow of fuel to the carbs? The vacuum on my petcock has failed and while the bike is running there is nothing to stop the fuel overflowing the carbs.

[@brunos1368]

Hey I have a 2006 ninja 250 pulled apart my bike to clean my carbs today and when I went to unplug the hose of fuel tank my petcock was leaking gas very fast on the ON position, I was watching a video where they said that if it leaks on the ON position it’s faulty. My small vacuum line next to it is not connected to anything is that normal?

[@dieseltu1035]

​@@tonalambiguity3345it doesn't regulate fuel. It opens it or closed it . By a manual valve.

[@paulwoods682]

@@tonalambiguity3345 In that situation you rely on the needle and seat in the carb to regulate the flow of fuel. Usually while the engine is running this works pretty well, can flood when the bike is stopped..