Fuel Tank Pressure? 99 GP800

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  1. #1
    Frequent Poster
    Join Date
    Feb 2014
    BC Canada

    Fuel Tank Pressure? 99 GP800

    Finally got some hot weather this summer. I fired up my 99 GP800 yesterday for a run. About a hour rip. Lots of wide open top end speed. Seemed to run really good. Got home and pulled the plugs for a look. Pic attached.

    Mag side and PTO side marked. As well as compression test numbers. I’m not super-versed in plug reading. I’m comfortable seeing darker plugs. The PTO side plug is certainly cleaner. Any reason for concern here?

    My understanding is the fuel tank is pressurized by return fuel from the fuel pump. If not holding pressure could contribute to a leaner mixture. Looking around at the tank check valve and gas cap seal, things visually look ok. Has anyone pressurized their tank and took a reading and leak down test? What PSI is recommended? I have a crankcase tester pump and gauge. Thinking I may rig it up.

    I’m pre-mixing about 40:1. 6 hours run time so far on an engine rebuild. Thx for any advice.
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    Last edited by keithb7; 08-01-2020 at 09:27 AM.

  2. #2
    PWCToday.com Is My Home Away From Home Chester's Avatar
    Join Date
    Feb 2002
    Vancouver, BC Canada

    Re: Fuel Tank Pressure? 99 GP800

    Ther fuel tank is not pressureized by the return from the fuel pump. It's pressureized from heat. A pressureized tank is not needed to run properly, it's just the result of PWCs being required to not have the tank vented to atmosphere. If you could keep the water out, you could ride all day without the gas cap on and it would not cause any issues. (do not do this).

    Speed is very expensive. How fast do you want to spend?

    Stand up:
    98 SXi-Pro


    96 XP
    86 X2

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