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Engine guru's

  1. #1
    Member Zero's Avatar
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    Engine guru's

    I have some ideas with this problem, but looking for more suggestions before the motor comes out. Here's the deal: 1986 Kawasaki Ninja 600r. Bike sat for a few years, so the carbs were completely cleaned out and put back together. The bike starts right up and idles great, but after it gets up to operating temp it starts to run rough (like not on all 4 cylinders). I figured maybe take it for a ride and open it up to see how it goes. The same thing happens (starts to run rough at idle and wants to stall when taking off.) So I pull back into the garage and do a compression test: 120, 120, 65, 125 on cylinders 1-4 respectively (spec is like 110-170). Then I do a leakdown on 1-4 cylinder 4 is 14% leakdown and 1-3 are 70% or more leakdown, so now I know I am in trouble. Would these kind of numbers lead to the symptoms that I am having or do I have two separate problems. Also what was interesting is that when I test cylinder #1 air escapes through the cylinder #4 sparkplug hole. So any ideas or suggestions (further tests?) before I tear into the engine. I am thinking new headgasket and possibly rings.

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  2. #2
    Dictionary quoting knob stoinkythepig's Avatar
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    Engine guru's

    The poor running when hot might be due to fule starvation from a blocked gas cap vent. When it starts running poorly, stop and open the gas cap. If it makes a sucking noise and the bikes runs fine after you will know for sure that the cap is blocked. The problem may also be caused by a bad hall effect ignition pickup coil. They are known to fail intermittantly with heat.

    The compression issue could be intake valves. They are a known problem on that bike. They were made too soft and sink into the head with use. If you have run out of adjustment on the intake valves, you'll know for sure thay are bad. Fortunately, they are pretty easy and cheap to replace. I have the tools and know-how to help you out if you need it. Nice benefit of soft valves is that the valve seats don't wear much at all and a good lapping is likely all they'll need to seal well. If the rings are worn, they should be easy enough to change while you've got the head off.

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  3. #3
    Just Registered TLRMan's Avatar
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    Engine guru's

    This one has several probs....

    Leak down and comp test don't make any sense. If you are getting air to #4 cylinder from #1 you def got a head gasket that went south. Does this engine have any kind of emission stuff on the exhaust? that tie the exhaust ports together? Reason I say this if you got #1 TDC, #4 is TDC but on the exhaust stroke. so your exhaust valves will be open. If your exhaust valves leaks, on #1, it maybe passing it on thru the tube. If it doesn't have that emission stuff on it, your head gasket went south, or north...

    anyway #3 looks bad on the comp test...did you try squirting some oil into the cylinders and do a comp test again? if comp rises, then it's your rings, if it doesn't then, it's your valves... (called a wet/dry test).

    Leakdown is all over the place too...I would look at both ends.
    You gotta pull the head anyway to get to the valves, so if your head gasket is popped, you gotta go that route anyway...I think your rings are probably toast too...just punch the bad boy out one size, clean up the valves, and have a hellava up coming season!

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    Too old to rock and roll, too young to die.

  4. #4
    Member Zero's Avatar
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    TLRMan:

    You may be on to something. The 600R has a 4-2-2 exhaust and I have SuperTrapp mufflers on the ends and I am now thinking it could be possible for air to leave the exhaust valves on cylinder #1 and back up into cylinder number 4 which is at TDC on the exhaust stroke. The thing is with 70% leakdown there is air comming from everywhere. Cylinder #3 is 90% leakdown. I think the head will come off so I can clean off the valves an lap them in.

    Thanks for the tips. This is basically my first shot with the leakdown tester. The plugs look clean (not wet) so maybe nothing is cracked. Things do get much worse as the operating temp climbs up though. As far as the summer is concerned I have a TLS, this is just a project for me so I do not want to spend a lot of money.

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