Fuel petcock screw torque?
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Thread: Fuel petcock screw torque?

  1. #1
    Member smthng's Avatar
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    Aug 2010
    Jacksonville, FL

    Fuel petcock screw torque?

    Hey all, does anyone know what the torque specified by Yamaha in the service manual is for the screws that attach the petcock to the tank?

    I tried "reasonably tight" and it leaked. I did "really tight" and it leaked. I bought a new petcock and tried both the previous and it leaked. I know some stuff will leak if over-tightened, so I want to attempt whatever Yamaha recommends before I start resorting to sealants and/or "RFT". Tank is clean, screws are new, no rust, tried fuel-safe thread sealer, with and without fiber washers, gasket is new, etc. If Yamaha doesn't spec a torque, I'm happy to start taking advice, using an impact wrench, whatever. Thanks!

  2. #2
    Senior Member Gastone165's Avatar
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    Dec 2017
    Western Washington
    I just replaced mine two hours ago. When I removed the old one the screws didn’t seem to be too tight. The paint under the original petcock appeared to be degrading so I cleaned the area with some scotchbrite. It looks like they may have had some type of sealant applied at the factory when it was originally installed so I wanted to remove that. I had to take a Stanley knife and trim off the old fiber washers under the screw heads from the old petcock because I didn’t get any new ones with the new petcock, they were stuck to it. I installed it with a firm application of a large Phillips screwdriver, but nothing extraordinary. It doesn’t appear to be leaking so far.
    You may have a rough surface or something under the rubber seal. Try smoothing the tank surface with some Scotchbrite.
    1972 Yamaha DT 175, 1974 Kawasaki 125, 1976 Suzuki TM 250, 1979 Yamaha 750, 1977 Husquvarna 360, 1979 Husquvarna 250, (2) 1980 Suzuki RM 400’s, 1971 Husquvarna 400, 1983 Honda V65 Magna, 1987 Suzuki 230 Quad, 1987 TW200, 1990 TW200, 1996 Honda XR 650, 1998 Yamaha 300 King Quad, 2000 Harley Davidson Heritage, 2006 Kawasaki KLX 250s, 2007 Arctic Cat 650 Quad, 2010 Polaris Sportsman 850 Quad, 2006 Yamaha Grizzly 660 Quad, 2002 TW200, 1995 TW200, 2008 TW200, 2016 TW200.

  3. #3
    Senior Member RockyTFS's Avatar
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    Feb 2011
    Hailey, ID
    I don't think there is a torque spec for this. I used a large Phillips (one place on a TW you can get away with that instead of a JIS driver) and used both hands to get it somewhere between reasonably tight and really tight (technical jargon). I sure would not use an impact driver! Something else is interfering with a good seal, not torque.
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  5. #4
    Senior Member Rider21's Avatar
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    Aug 2015
    Reno, NV.
    Standard torque value of a 6mm bolt or screw is about 7 ftlbs.
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  6. #5
    Senior Member Smitty Blackstone's Avatar
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    Sep 2014
    Mamaroneck, NY
    Start with snug, then proceed further.

    Of course, you should exhaust all forms of surface preparation first.

    If that fails, then Yamabond or Gasoila is your friend.

    Don't use silicone.

  7. #6
    Junior Member Thetrainer's Avatar
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    Jan 2016
    North East
    Ditch the crappy Philips heads and get some stainless steel bolts. I ordered a kit from fleebay and did the engine and had a few left over for the tank. Get a kit for about $25 you will not be disappointed.
    87 TW200 w/ TRI-z front end
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  8. #7
    Member smthng's Avatar
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    Aug 2010
    Jacksonville, FL
    Just following up...

    Quote Originally Posted by Rider21 View Post
    Standard torque value of a 6mm bolt or screw is about 7 ftlbs.
    I found my old FZ1 service manual and it agrees with 7ft/lb for that size screw/bolt. So that's the "official" Yamama answer. That's slightly more than finger tight, IMO. Found my micro torque wrench, converted to inch-pounds, installed to spec... useless.

    Got some Gasoila E -seal, which helped, but still leaked. Tried some other screws I had lying around, scrotchbrighted both surfaces, tried neoprene washers, cut up pizza box cardboard washers, drilled the SAE washers the local hardware store had out to match the metric cardboard ones from the old petcock, bought new unnamed petcock, etc. Still leaked.

    What eventually saved me was this:


    It's a Husky Pro (Home Depot) Microdriver ratcheting hex bit wrench set which is no longer sold. The closest Husky thing I can find online is a "Husky Swivel Speed Z Hex Bit Wrench (21-Piece)". It doesn't look quite as small, but it'll probably get the same kind of jobs done. It looks like a non-Husky version of the thing exists on Amazon without the bits, and there's a GearWrench thing that's similar, but might be a bit larger. Anyway... this thing is the tool I often end up tearing apart my garage to find. It was the only screwdriver that would let me get enough torque on the screw to tighten and still turn in the cramped spaces after the tank and petcock were installed.

    I scraped the two old cardboard washers off the petcock, flipped them over and reinstalled the petcock with some Gasoila on the threads. I then tightened the two bolts to "snug" and just kept coming back every hour or so to turn them both about a quarter turn (using the wrench above) until everything stopped leaking. Six hours later, all was good. Two days later, still no leaks. 200 miles later, still good.

    Thanks everyone for the suggestions and for pointing me at Gasoila... I'm sure it helps.

    Edit: Just for reference, by the time I was done, I was at "expecting screw head to shear off" levels of torque... I didn't have much left to lose.
    Last edited by smthng; 03-12-2018 at 09:37 AM.
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