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Thread: This Rex is giving me grey hairs.

  1. #1
    Join Date
    Sep 2005
    Posts
    90

    This Rex is giving me grey hairs.

    G'day! I'm sure some of you have experienced something similar to this so I'm hoping you can help me out!
    When I bought the Zrx a few months back I noticed it had a little issue with petrol getting down into the crank case but only when it's running. When it's sat in the shed not running, it doesn't leak at all so I'm inclined to rule the fuel tap out (plus when the tank is removed and left in the "on" position, it doesn't leak). When I bought it, the previous owner had K&Ns on and a straight through Mivi can on the exhaust. I was a little suspicious as to whether the carbs were rejetted to suit. I decided to put the bike back to standard so I fitted a standard air box (who knew it could be such a twat!) And I rebuilt the carbs with all the standard insides along with a clean. I put the float levels to 18.5 which I heard somewhere was standard, and the air / fuel mixture to 2 turns out.
    After a swift oil change, and a couple of test rides, it seems to run sweet enough but I'm still getting the dreaded oil contamination of petrol.
    Can anyone shed any light on what the problem might be?
    Thanks!

  2. #2

    Re: This Rex is giving me grey hairs.

    Float valve seals sticking

  3. #3
    Join Date
    Jul 2017
    Location
    South from the Deep South
    Posts
    2,885

    Re: This Rex is giving me grey hairs.

    Well, I would suggest re doing petcock first to eliminate it as possible culprit. Anything else would require you to go back and rework the carbs.
    Polish onslaught

  4. #4
    Join Date
    Sep 2005
    Posts
    90

    Re: This Rex is giving me grey hairs.

    When I rebuilt the carbs I changed the float valves so I think I can rule that out.
    I'll give the fuel tap a whirl and see where that gets me. Cheers!

  5. #5
    Join Date
    Jul 2017
    Location
    South from the Deep South
    Posts
    2,885

    Re: This Rex is giving me grey hairs.

    Quote Originally Posted by Srednas View Post
    When I rebuilt the carbs I changed the float valves so I think I can rule that out...
    That may still happening if there is particulate contamination coming from the tank or fuel line... Anyway process of elimination. See if petcock fixes the issue ...
    Polish onslaught

  6. #6
    Join Date
    Jul 2008
    Location
    the Netherlands
    Posts
    5,398

    Re: This Rex is giving me grey hairs.

    aftermarket float valves are supposedly a no-no too, though getting fuel down the bores with a running engine seems unlikely to me, unless it's not running on all 4.

    a new o-ring in the petcock is a easy fix at least
    ships get called 'she'
    I bet torpedoes don't

  7. #7
    Join Date
    Jul 2017
    Location
    South from the Deep South
    Posts
    2,885

    Re: This Rex is giving me grey hairs.

    Quote Originally Posted by gunther View Post
    ... though getting fuel down the bores with a running engine seems unlikely to me....
    It's called "making oil" in the boating world...
    Polish onslaught

  8. #8
    Join Date
    Oct 2008
    Location
    Perth Australia
    Posts
    64

    Re: This Rex is giving me grey hairs.

    Look in the air box with filter removed. Look for signs of fuel draining into crankcase through the engine breather , or even look in the oil collector that hangs by the water pump. Will smell of fuel. I took the petrol filler cap one way vent out to stop pressure build up which I believe caused my seals in number 2 carb to fail . Merry Xmas all

  9. #9
    Join Date
    Sep 2005
    Posts
    90

    Re: This Rex is giving me grey hairs.

    All good ideas.
    I'm going have a rummage around this weekend and fit the new o-ring in the petcock along with checking your other conclusions. I read something on one of the other pages on here about someone who had a similar problem that boiled down to a straight through pipe making the bike run more rich? Might have a tweak of the fuel / air mixture while I'm there too and see if that sorts it.
    Hope you've hall had a good Christmas and a happy new year to you all!

  10. #10
    Join Date
    Jul 2017
    Location
    Essex
    Posts
    589

    Re: This Rex is giving me grey hairs.

    Quote Originally Posted by Srednas View Post
    All good ideas.
    I'm going have a rummage around this weekend and fit the new o-ring in the petcock along with checking your other conclusions. I read something on one of the other pages on here about someone who had a similar problem that boiled down to a straight through pipe making the bike run more rich? Might have a tweak of the fuel / air mixture while I'm there too and see if that sorts it.
    Hope you've hall had a good Christmas and a happy new year to you all!
    Just a small idea if you're interested in 100% preventing any problems from a leaking petcock in the future.

    Since the bike has a fuel gauge I've never been bothered with the reserve, so when I serviced the petcock I simply crimped over the long fuel pipe and sealed it completely. This essentially then gives you an 'off' setting for when you want leave the bike for any length of time and don't want the risk of fuel draining into the carbs.

    So your ON setting becomes OFF, PRIME stays as PRIME and RES is your new ON.

    I re-labelled the dial of course so it's not confusing as it sounds. It's not for everyone as some like to keep the reserve function, but I like to have fuel cut-off option for storing the bike.

    I say it's a 100% fix, but that doesn't remove the human error if you forget to turn it to the off position when parked up of course

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