KZ1000A2 Low Compression

[andyb]

I've recently bought a KZ1000A2 with 31k on the clock. I haven't ridden it in earnest yet but it starts well, and runs and revs freely, no nasty knocks. I noticed some oil residue around the front of the cam-chain casing (see photo) so decided to carry out a compression test, the results of which are
#1 - 55 psi
#2 - 65 psi
#3 - 60 psi
#4 - 60 psi
These seem very low to me, I'd expect upwards of 150 psi in a standard set-up. At this stage I'm ruling out a blown cylinder head gasket as I'd expect this to affect probably 1 cylinder only, not all 4. I'm therefore thinking that stuck piston rings is a more likely culprit so will try soaking them with Sea-foam for a couple of weeks. I've recently changed the oil so will drain the engine first before adding the the Sea-foam. I'll also level out the pistons to the same positions in all cylinders beforehand.
I'd be interested to know if anyone else has noticed such low compression on their Zeds and how they tackled it. If it needs a top end strip down so be it, I'll tackle that later. I figure that I've nothing to lose trying the Sea-foam first as this may solve the problem.
Thanks in advance for any tips and suggestions.

andyb

[zed1015]

I'd re check your comp readings.
Around 90psi is needed for combustion to occur and at 65 psi you'd be lucky to get it started.
If it's been stood then the valves are likely not seating fully and the rings may be gummed so i'd probably just run it a while to see if it perks up before pulling it apart..

[warren3200gt]

65psi is very low even on a cold engine. Were all the plugs out and holding the throttle wide open and turning over using a well charged battery? I've never seen a Z engine, even an absolutely shagged one read below 80psi.
.Additionally test your test equipment. Couple it up to a known psi output on a compressor and make sure both read the same. I've seen compression guages where the schrader valve has been swopped out for a tyre schrader valve. They are not the same. Tyre schrader valves will cause the compression tester to read extremely low.

[DeadZedDave]

Plus 1 - what ZED1015 said. If its been stood - just run it a bit !