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half the compression 96 zx6

Discussion in 'Technical and Troubleshooting Torque' started by BlueRex, Jan 25, 2008.

  1. I recently purchased a 96 zx6r with 92k on the clock.
    I don't know what a zx6r is meant to feel like but it seemed ok to me.

    Today it went in for it's first service and was told it has half the compression it should. I have been advised that it will cost 2k to fix.

    Now i only paid 2k for the bike, spent another 800 on new fork seals and new tyres.

    My dilemma... is it worth spending the money to fix or should i sell it for what i can and put the money towards another bike?

    Your thoughts?
  2. Second opinion, especially if teh bike seems fine.

    Regards, Andrew.
  3. I would normally agree but having not ridden another bike apart from my 250 i can not really compare.
  4. That's why you need a second opinion. Without actual compression figures, it is impossible to say.
    However, if they say "half of normal compression" and the bike runs fine, then they're full of it. No engine will feel fine with 50% compression of new (I doubt most would start at that).

    Regards, Andrew.
  5. Re: half the compression

    Some worthy folks forget to drop some oil down the plug hole while doing a compression check.

    $2000 does sound like a lot of money for what might only be a set of rings... or a valve grind. Hey, maybe the valve adjustment(s) are out, too. ;-)

    Get another estimate.


    Trevor G
  6. Agreed. If it was half compression, you would be having some pretty fk'ed up issues with engine operation. Take it to a kawa dealer and get them to run-up a quick test on a dyno.
  7. It was a Kawa dealer :) It seems to be the general opinion that i should get a second opinion so i will look for another mechanic.


    He did say the compression should be 250 but was getting 95, 125 90 and i think 130
  8. Means nothing.

    You need to get a second opinion. You also need to get a record of the individual cylinder readings.

    The reason for this is that a compression test is useful for diagnosing problems with individual cylinders. The absolute readings are generally less important/significant that one cylinder's reading is out of whack with the other three.

    An engine so tired as to have half new compression will give poor starting, particularly when hot, smoky exhaust and/or regularly oiled plugs.

    If a proper comp test shows all four cylinders as being within about 20% of each other and the bike is otherwise behaving itself, I'd be inclined to enjoy it as is rather than "breaking the seal" and spending serious money.
  9. I agree with the 2nd opinion line as if its true it should be blowing a heap of smoke, have no grunt under load and be difficult to start.
    There is a fair chance the rest of the bike will be showing signs of being r00ted too.

    Shop around.
  10. It is not blowing any smoke at all, it starts first time every time and seems to have plenty of grunt it is a bit lite on when first rolling of from the lights but i thought that was because it's torque range is higher.

    Thanks for the feed back guys
  11. yeah those arnt good numbers,if they where all 90 ur bike woudnt start, 2k he prob want to do rings,pistons and hone barrel,

    Id get a secound opinion and make sure the vavles arnt leaking, its a relativly cheaper fix.
  12. Bluerex,

    If the engine still feels the same as when I sold it to you, then the power is fine for a 600. I have ridden a few other 600s of similar age, and that ZX6R had as much power as any of them.

    Get that second opinion, my mechanic saw that engine at about 86000km and was impressed by its condition, stating that he thought it would be good for another 86000km,
  13. It hasn't changed since i got it from you. My second opinion was going to be your old Mechanic, i will call them first thing on tuesday.
  14. got the results back these are his comments

    motor very tired 45-85% leak down

    wtf is leak down?

    Ht comp test #1 122 #2 90 #3 95 #4 120
  15. not looking good, new engine time i reckon.

    When he did the leak test the mechanic should be able to tell (espaecaily with those leakage numbers) exatcly what is wrong as u can hear air coming from either carbs exhust or breather.

    BTW leak down is when the blow compressed air into the barrel and it supposed to only leak about 20-30% any more and ur in shit.

    like i said before it might be the vavles as opposed to rings and barrel, which is about 1000$ worth of work, and thats looking like best case scenaroi
  16. Just ride it till its stuffed gonna cost ya just as much then :wink:
  17. +1 then sell it to me for $100
  18. Anybody telling you that a road engine burning petrol should have 250 psi compression is having a lend of you. Even 150 psi would be remarkable at cranking speeds.
  19. Are these the results from the first test?

    If it still feels the same as when you bought it, I dont think you have a problem,

    Unfortunately my mechanic has sold his business, but the shop is still running
  20. Yeah they are the results from the first test, i have not organised another one yet. After going for the ride down to Lavers hill yesterday i am starting to doubt i have a problem too.