No compression on all cylinders

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Siuras
Posts: 4
Joined: Sat Jul 23, 2016 8:59 pm
My Bike: ZXR400 L3

No compression on all cylinders

Post by Siuras »

Hi, I did an engine rebuild by myself. I have changed almost everything.. Just valves left the same, and I have no other idea what check yet.
First time I checked pressure and on all cylinders were about 4bar after added oil pressure jumped up slightly to 6 bar. I have split the engine again, all valves haven't been lapped and pistons were 180' turn over. I have fixed that and put on the head gasket Shellac. Now is no compression on all cylinders, head was well torqued 2x. Do you think piston rings shall work some time on honed surface to get seal?
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Miles
zxr400 oc member
zxr400 oc member
Posts: 498
Joined: Wed Apr 30, 2008 11:00 pm
My Bike: ZXR 400 L3
Location: Bangor, Northern Ireland

Re: No compression on all cylinders

Post by Miles »

If your head gasket is ok then you could have what I had.

I rebuilt my engine several times because my tester told me I had low compression. Couldn't work why as everything was refreshed and new.

Took it to the mechanic and he also found low compression. Turn out to be my and his testers.

The spark plug tunnels taper in and the compression tester would catch the top threads and not seal.

He machined a tapered adaptor, turned the engine and the compression shot up to 110-125psi
Siuras
Posts: 4
Joined: Sat Jul 23, 2016 8:59 pm
My Bike: ZXR400 L3

Re: No compression on all cylinders

Post by Siuras »

Hmm head gasket isn't scratched, looks very well. I'm not sure about the head surface that's why I added Shellac head gasket. When I took off valves I made minor signs here and there.
I bought M10x 1.0 tap and retapered spark plug's threads.

Tomorrow I'm going to check valves clearness again, and plug in other compression tester.

That's strange.. When I put onto barrel my hand and turned crankshaft that It sucked hard. I just hope it isn't piston rings problem.
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