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998 998 Died And Will Not Start: Solved! Timing Off

Discussion in '748 / 916 / 996 / 998' started by twd46, Sep 1, 2021.

  1. So after replacing my clutch plates and basket, I was able to ride my 2002 998 for a total of two days before it quit and it hasn't started since. I downshifted and it quit. I assumed i had simply misshifted since the clutch felt differently. But I went to start it back up and it wouldn't start and hasn't started since. The fuel pump primes, engine turns over, I have spark, but it will not start. It stumbles a bit as if it is going to start, but will not do it.

    Below is a list of everything I have checked and/or replaced.

    -fuel filter
    -spark plugs
    -drained fuel (I suspected bad fuel)
    -fresh fuel and fuel injector cleaner
    -checked side stand bypass and it is good

    i am suspicious of the battery cables. I had only one other starting issue about a year and a half ago and it was due to bad connections on the battery cables. I took them off and cleaned the mating surfaces and it started immediately. There is a crimp in the positive cable as well.

    I am out of ideas and I would really appreciate any help.
     
  2. rather than just throwing parts at it have you checked the basics?

    do you have compression? have you checked for a spark? have you checked fuel is being injected?
     
  3. Yes, as I said, I checked for spark, and is getting fuel. It also has compression, but no I haven't checked the specific psi.
     
  4. If you have compression, fuel and a spark I put money on a split fuel hose in the tank.
     
    • Agree Agree x 1
  5. Thanks Petsmith. That was my first thought when I got home after it died. I removed the fuel pump assembly expecting there to be a split hose or a hose that had slipped off, but I could not find it. I even drained the tank and looked again, but everything likes fine.
     
  6. Have you looked in the tank with the fuel pump running to see if it squirts out where it shouldn't. What you describe, sudden stop, wants to go sometimes just sounds typical for low fuel pressure.
     
  7. I had a very similar problem... looked at all sorts of possibilities, even though Petsmith correctly diagnosed the issue straight away. o_O

    Feul line had come off below the filter. Does the fuel pump sound like it's building pressure? How old are your in-tank lines? There might be a split that isn't obvious.

    When you crank it, does it sound like this?

     
  8. Thanks for all the responses.

    The good news is that I found the problem, but the bad news is that the timing on the vertical exhaust cylinder is out. i have no idea why it happened and no idea what carnage awaits me.
     
  9. i'm guessing you mean valve timing? fingers crossed for you, if you do - I think you would have heard some unusual clatter or a resistance to turn while attempting to start if really serious.
     
    • Agree Agree x 1
  10. Ive got some weird stuff going on.

    The cam can push the valve down but the lobe gets stuck on the closer and will not turn any further. I checked the valves on the exhaust side and I can't get my smallest feeler gauge in there (.003).

    Here is a video of what it is doing:

     
  11. dropped a valve??
     
    • Agree Agree x 1
  12. :scream: but given the problem, sadly very possible. Andy
     
    • Agree Agree x 1
  13. Bent/dropped valve was where I was thinking o_O
     
  14. Bent valve.
     
  15. Ok. Thanks for your responses.

    So what now? Pull the head and replace the valves? Also check the piston for damage?
     
  16. And the valve guides and if its bent the rod
     
    • Agree Agree x 1
  17. So I've pulled the vertical cylinder, and there doesn't seem to be any damage to the piston, but I am almost positive the valves are indeed bent. I may install good valves, but I might just replace the head altogether.

    Ive found a decent deal on a 2006 999 head. I know the part number is different than for a 998 head, but will it work in any case? I assume a 1098 head won't work because of all the differences between it and a 998 head.
     
  18. 1098 head is totally different.
     
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