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Thread: Crushed plug

  1. #1

    Crushed plug

    Huston, we have a problem!

    On a whim I checked my plugs today and found the #1 plug to be jamed shut.

    Funny, during last weekends enduro of two 50 mile runs, after the first few minutes of perfect running at around 7800 rpms, it suddenly dropped to 7450 for the entire rest of the ride. Also it had a rough idle after the first half that I attributed to being out of fuel. If this happened early on, that means that I ran the entire race on three cylinders.

    Also when looking down the plug hole, I believe I see dents in the piston top.

    All other plugs are fine, but number 2 looks rich where the others are white. Compressions are compatible to each other, but are on a cold engine so they are low. 90 100 95 100.

    Ideas? I'm getting ready to tow it back to my dealer to see what they think.
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  2. #2
    Your plugs probably deformed during the race not before I'd imagine.
    If the piston didn't hit, I bet it's the heat, too much of it, like running way too lean.
    Your compression numbers are really low, about 50 psi less than normal (possibly gauge out of calibration). But at least they are somewhat uniform which is important.

    BTW, your plugs look better than mine!


  3. #3
    I doubt the Pistons are hitting those plugs; I bet they would be really busted up if that were the case. I agree with Mean; it has to be heat related. I have seen alot of Plugs from Ultras . . . and these Plugs look "lean" to me. Is your boat Stock?

  4. #4
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    If this is a 300 looks normal color wise mine are the same lean looking well with out the melting lol

  5. #5
    Yes, stock 300X with about 20 hours now. Only mods are washers and a secondary oil catch can.

  6. #6
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    Maybe you got some bad fuel ?

  7. #7
    UltraKvz's Avatar
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    My 260x did the same thing to #1 and #2 plugs. My dipstick were blown halfway out too and the o-ring on the oilfilter blown out at one side. All the oil drained into my hull. Long story short: complete engine rebuild due to my impeller coming loose and pushing driveshaft against crank and boom! Trying to upload pics of the plugs.


    ***stupid bberry pic won't upload, but looks the same as creator's pics except mine were golden brown****
    Last edited by UltraKvz; 11-04-2011 at 04:30 PM. Reason: disfunctional cellphone

  8. #8
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    My dip stick always pops out its zip tied in now

  9. #9

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    crushed earth electrodes are usually bad news.

  10. #10
    As for fuel, I was running a 3:1 mix of 91 octane chevron to 110 race gas, freshly filled up.

    No problems with the dip stick, but other than the normal mess from the catch can in the front storage area, there is some oil in the bilge that I'm not used to seeing.

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