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1982 Maxim 400 won't start

Discussion in 'The Garage' started by fusion1962, Jan 8, 2019.

  1. fusion1962

    fusion1962 XS400 Member

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    Purchased a 1982 Maxim 400 DOHC $50, came in 4 boxes. I have it together, tried starting, no bueno. I ultrasonic cleaned carbs and rebuilt them. I am getting fuel and spark and I have compression. New battery, starter turns strong. New plugs, both coils test good per the Service Manual. With fire (spark), fuel, and compression, what am I missing? Any thoughts?
     
  2. fusion1962

    fusion1962 XS400 Member

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    Also wanted to add that I have stock airbox and new air filter. Compression in both cylinders is 65psi with starter turning the motor. Won't fire, except occasional pop
     
  3. xschris

    xschris a lifestyle not a trend Top Contributor

    65 is way too low. You should have at least 120 and that's the low end. A good motor gets 150+. Do a wet test and see if it changes it. Also make sure to have the throttle wide open when doing the test. If nothing changes your valves could be bad. Make sure they are adjusted to spec and try again.
     
  4. fusion1962

    fusion1962 XS400 Member

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    Thanks Chris, I will pop the top and check valve condition/clearances after wet test. The thing that puzzles me is I am using a decent screw-in type compression tester and I get identical 65 psi on both cylinders. What are the odds of both reading same? Just a thought... thank you for advice, seems like good direction due to my plugs got fuel-soaked, tried brand new plugs, same result...
     
  5. fusion1962

    fusion1962 XS400 Member

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    Update: Did a wet compression test and now my compression on both cylinders is 10 PSI (??) When I hit the pressure relief button on the compression tester, fuel sprayed everywhere. Did I just ruin my tester or? I was getting 65 PSI on previous tests, so I'm guessing I need to try a different tester. Anyone else ever experience this?
     
  6. xschris

    xschris a lifestyle not a trend Top Contributor

    Is the motor full of gas? Make sure the motor has the correct amount of oil in it.
     
  7. fusion1962

    fusion1962 XS400 Member

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    The combustion chamber has lots of gas in it, I cranked the motor for about 15 seconds to try to get the compression up, but can't get a reading above 10 psi. Could the valves be that out of whack to go from 65 psi to 10 psi or maybe my compression tester is shot. I haven't tried a new tester. One other thought, could the timing be out enough to cause a no start? This of course has solid state ignition (no points)
     
  8. fusion1962

    fusion1962 XS400 Member

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    I will re-check oil level...
     
  9. fusion1962

    fusion1962 XS400 Member

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    Oil level is correct
     
  10. fusion1962

    fusion1962 XS400 Member

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    My fuel levels with the carbs leveled D3A2C414-58DD-49B4-BEC4-3B9D90C587BE.jpeg
     
  11. xschris

    xschris a lifestyle not a trend Top Contributor

    I would be worried about the very poor compression numbers. Without that nothing will happen.
     
  12. fusion1962

    fusion1962 XS400 Member

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    I agree, I’m puzzled that the readings are that low, I will check valves
     
  13. fusion1962

    fusion1962 XS400 Member

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    Update: Got it running for first time! I found out that you can’t trust how things are marked when you get a 37 year old bike in boxes and try putting the pieces of the puzzle back together. The #2 RH spark plug wire was marked #1! I swapped wires and voila! Fired right up. Obviously my compression gauge is no good. It’s a good feeling to hear engine running
     
    Dblokxs4 and xschris like this.
  14. fusion1962

    fusion1962 XS400 Member

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    53C0CE79-B712-48BD-AFB0-BAA55A02ACF5.jpeg Current state of project
     
  15. xschris

    xschris a lifestyle not a trend Top Contributor

    Might be a good idea to get another tester just to see where it's at for numbers. It will give you a good idea on the condition of the top end.
     
    fusion1962 likes this.
  16. fusion1962

    fusion1962 XS400 Member

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    Will do, thanks Chris
     
  17. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    I would get low compression readings if I didnt open the throttle when performing the test. I try to do it with the carbs off completely. ITs also not a good idea to keep a bunch of gas in the combustion chambers. The gas will wash the oil and you will get scoring/rusting. I usually keep a can of fogging oil handy for this.

    Its crazy how durable, yet fragile engines are.
     
    fusion1962 and xschris like this.

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