Cylinder compression test - failed ??? :(
- steell
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If you didn't rotate the motor one complete revolution between testing number one and testing number two, then one of them was on the exhaust stroke and the intake valve was open. Number one the way it sounds.
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- 650ed
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Bunty27 wrote: OK, so I did the poor man's compression test with cylinder 1 that I managed to mess up with my hand trick and viola, I could clearly feel a lot of air coming out of the open carb intake (I took the carbs are out). I repeated the test on cylinder 4 which I did not mess with and I couldn't feel air escaping out of anything, especially not out of the carb intake for sure.
So it's certain that by putting my hand over the carb intake while doing the compression test, I managed to mess things up. But the question now is what is it that I did to that one cylinder and what can I do to fix it? Gurus, please help!!!!!!
Not possible unless you dropped something inside the intake port. Consider this - when the carbs are on and the throttle is closed there is only a very small opening for air to pass through, not unlike having your hand over the intake. If you are feeling a lot of air coming out of the intake I would guess your intake valve is not closing all the way. Is it possible you had a piece of rag or paper towel or something else in your hand that got sucked into the intake? Can you peek in there through the port to see if any obstruction can be seen? Ed
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- Bunty27
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- lemo32
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- Bunty27
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- Motor Head
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No you can't remove the valve, by only removing the valve cover. The cylinder head would need to be removed to change valves. Look in your port, of nothing there, check valve clearances. I would also verify correct cam timing while your at it.
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- Paroxyst
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- KZ550 -82 B3. KZ550 A1. ZX550A1. CBR600F2
And no you cannot remove a valve by removing the valve cover off and if your not familiar with rebuilding a cylinder head including valve clearance and cam timing then you better think a couple of times before diving into it. It is perfectly doable if you have little more then basic mech skills and a complete rebuild manual. I think the leak down test is a bit over the top at this time for you. The important thing is that you get a regular compression test done - after those number are in we can take it from there. And again - it IS impossible to ruin something by holding the hand over the intake so you can put that to rest.
I am more worried about your pistons and that´s why you have to get a reliable compression test.
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- Patton
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The poor man's leak down test (introducing compressed air into a spark plug hole and listening to where it escapes from the combustion clamber) may be done at TDC (top dead center) or any other cam positions where both valves are fully closed and supposedly not leaking.
Top dead center (TDC) is when the piston is at its highest position. An easy way to tell TDC is by alignment of the T mark with the case mark when viewed through the timing window.
Would then repeat the poor man's leak down test in #1 cylinder after first being positive that the piston is at top dead center (where both the intake and exhaust valves are supposed to be fully closed against their seats).
The leak down test helps determine whether fully closed valves are leaking (for whatever reason, such as zero clearance, burnt/damaged valve or seat, blockage between valve and seat, bent valve, incorrect cam timing, weak/broken valve spring, etc.)
Good Fortune!
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- Motor Head
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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
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- Bunty27
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I did look through the carb intake valves (using my iphone instead of the camera) and I did not find any choke flaps inside in any of the cylinders. In fact, all the valves looked the same to me. I'll try and share a picture soon.
I need to retry the compression test with a good compression gauge. Meanwhile, I drained the batteries out in the process of all this compression testing. I'll get the battery re-charged, retry the compression tests and share the results.
Thank you very much for all your advice here. You guys are awesome. I've decided to limit my work to the chassis & carbeurator. If there is something wrong with engine, I'll let some knowledgeable mechanic take care of it. Please stay tuned for my compression results.
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- 650ed
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- Nebr_Rex
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Bunty27 wrote: Thanks much Patton. I followed your directions and aligned the external mark to the T mark and repeated the poor man's air compression test. And thankfully, the air escaping from the carb intake does NOT happen any longer.
I did look through the carb intake valves (using my iphone instead of the camera) and I did not find any choke flaps inside in any of the cylinders. In fact, all the valves looked the same to me. I'll try and share a picture soon.
I need to retry the compression test with a good compression gauge. Meanwhile, I drained the batteries out in the process of all this compression testing. I'll get the battery re-charged, retry the compression tests and share the results.
Thank you very much for all your advice here. You guys are awesome. I've decided to limit my work to the chassis & carbeurator. If there is something wrong with engine, I'll let some knowledgeable mechanic take care of it. Please stay tuned for my compression results.
And make sure throttle is fully open and spark plugs removed.
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