Why Vacuum Petcocks SUCK! How they work and key failure points.
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- čas přidán 10. 05. 2022
- Vacuum petcock overview, why the suck and what is the common failure point? Care to wager on a $5 cent O-ring to prevent your engine from hydro-locking? Plus, how they work and then, some more Georgia trip video footage at the end.
Great explanation. Thanks
That gasket in back always was a problem, but easy to fix. Looking back it was simply the way, fast forward to water cooling, ABS, injection, inverted forks.....I really have been riding for 45 years! (I hate ABS, had an argument with it, all could feel was my foot pumping while I tried to skid sideways, and I'm trying to get more front....BANG!)
I’ve doubled the springs on them that closed the plunger when the engine is off, when a rebuild kit is available. Kind of weave the springs together to make one spring, reusing the original spring with the spring in the kit. The vacuum can still easily pull the plunger off but when the engine is off, it pushes harder against that o ring and the seat. But you’re right it’s still necessary to have a functional diaphragm. That’s not the failure usually though. They bypass the plunger and flood the engine out. The extra spring helps. I did a complete top end on a DR-Z400 couple years ago that smoked the rings and cylinder due to repeated overflowing of the engine. All due to a 5 cent o ring and spring that failed.
Welcomed info ! ..Does Pingle offer a non vacuum petcock for a 77 Suzuki gs750?
Nice to see the Vessel JIS screwdriver.
People wonder why they bugger up metric bike screws with cheap Phillips screwdrivers. Japanese Industrial Standard screwdrivers are a must for working on Japanese bikes.
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You can grind the tip on some phillips bits and come close enough to not wipe out the JIS
Great video. I'm having an issue with a fuel leak from the bottom of the petcock fuel line. Gas leaking from overflow and heavy into the air box and exhaust. First thought was float in carb but when I removed line from petcock to drain tank, of course gas poured out under prime, steady drip on reserve and a steady drip when "on". Does it make sense to have a drip only when it's "on"? Not sure if i should replace internals on carb or get a new petcock
No, it shouldn't. It's bypassing the fuel cock. Start there and repair that first. Then go to the carbs because the float valves shouldn't overflow that easily or that quickly.
Outstanding video! Are rebuild kits any good for these vac petcocks? I have an '82 Kawa KZ440 that has a bad vac petcock. Can't find an exact replacement. I have found rebuild kits for it on Amazon and Ebay.
Thanks. Consider subscribing and like/share. Check with Z1 Enterprises and/or Z1 Parts (Z1 parts.net). If you’re looking at a K and L brand kit that’s the only aftermarket I will use unless I’m really stuck. Made in Japan. You could eliminate the thing altogether and go with a Pingle Enterprises manual petcock. They’re pricy but excellent quality. US Made. Those $28 dollar Chinese petcocks are junk stay away from those replacements.
@@MotoRestoFL Thanks for your reply. Looks like Z! has what I want. Thanks for the info. New subscriber coming up.
The first thing I did after Buying My 82 XJ-750 is get a Gravity Petcock.
Pingle Enterprises. Best petcocks available.
Technically this particular one could be made into a manual fuel tap quite easily. If you blocked off the vacuum side port and ground off the tab on the plate by the reserve position, then the handle would be able to be turned all the way pointing up, which would be a manual ON. The reserve and prime positions would both serve as reserve and the ON position would be OFF.
Of course, this would have to be labeled properly on the face plate, otherwise everything is backwards and would not make sense to anyone but the person that modified this tap.
Yes. You are correct. I failed to mention that. Thanks.
Wish someone made a replacement one with an on, off, and reserve! These can be a pain in the ass!
Sometimes, there is. Depending upon the bike or whatever it is, checking the forums on that particular make/model can show a compatible fuel cock, non-chinese junk, an original like a Suzuki or Yamaha that does have on/off/reserve. For example, I had a DR650 back in the day, and found that I think a Yamaha fuel cock was exact same size, off a Yamaha whatever it was... ordered one new and installed. Worked perfect. I put a stick on label right on the speedo glass at the bottom, labeled FUEL which reminded me to shut it off when parking the bike. So there may be options that will interchange, unfortunately, I know no clearinghouse of info that will direct you. It may take some research.
Oh, and by the way, someone does make one that's not junk, I mentioned it at the end in text. Pingle Enterprises. They are U.S. made and super high quality. They are pricy but not terribly so, for example, I priced one out for a customer's VTX1300 and it was just a shade more expensive than a brand-new OEM.
@@MotoRestoFL PINGLE is the way to go. They are the best bar none.
From my experience vacuum petcock failure generally results from fuel tank issues. Shit tank coating flaking off, or rust seem to be the major cause of failure.
Also a manual petcock is not a godsend either. Crap can get past them and into the carbs. You turn on the manual petcock so now you have direct flow, or prime on a vacuum petcock. You have a float valve in a carb stuck open, hello hydrolock...unless you have overflow tubes on the carbs.
Like he said, Pingle is a quality alternative. I have a ZRX 1100,and there is a very active ZRX community that has a bunch of folks who make parts to mod your bike. One of them makes and sells a lot of parts for performance and light weight. His site is Expensive Lightweight Stuff. He sells a manual petcock that has a titanium faceplate. On/reserve/off. No vacuum hose. Kawasaki has a lot of compatible parts, so it probably fits many tanks. This GPz petcock looks a lot like the ZRX one.
And if not perfectly straight, leaks, and you only get a couple tries before you damage the flimsy diaphragm.
I've always felt Vacuum Petcocks were stupid. Gravity Works fine, it just adds complication to a process that doesn't need to be complicated. Just doesn't make sense.
Could you make a simple thing more horrendously difficult to figure out 😵💫
Yes. I could.