compression problem

[tomtom]

I used a Cometic sprung steel head gasket on my 1100 about 3 000 miles ago after a full engine rebuild. Everything great then bike won't start one day. Did the usual checks and no success. Checked the compression and it was way down on 3 cylinders beyond usable. Have the head off and no holed pistons thankfully but has anyone come across such a short lifespan of these gaskets. It's only used on the road. Are copper gaskets better. Thanks.Any other thoughts would be helpful.

[Pedda]

Sprung steel gaskets are excellent. I don't suppose it to be the reason for your loss of compression. I'd check valve seats or rings.

[Katgeezer]

Agree with Pedda, Cometic are among the best there is altho' for a standard engine most would probably use OE gasket as the Suzook ones are brilliant. Can't imagine the gasket being the problem.

Rings or valve gear most likely.

Were you using much oil when it was running? I presume you didn't disappear in a cloud of smoke every time you pulled away.

[tomtom]

Valve stem seals and new rings and bores honed only 3000 miles ago. Was working one day and not the next. Surely a bit too much coincidence if compression is suddenly down on 3 out of 4 bores. Scratching my head on this. Any other ideas please.

[FBJ]

Tomtom. Turn the head up side down and fill the valve pockets and see how quickly it leaks out.

[Katgeezer]

So you're happy the basics are ok so maybe we need to go deeper.

How about the camchain tensioner,does it seem to be ok? Thinking jumped tooth here guys, anybody else agree?

[Pop-Kat]

Can't see it being the cct chris.

If you use a copper head gasket you really need to have the block piano wired to seal in compression, it'll work good then but you might suffer annoying oil leaks. Use a std gasket if your on std bore. As for your compression problem, is your tester good ? Are the plug threads good ? It could have just flooded (fuel tap diagram) then a non accurate test shows low comp. not saying that's what's happened, just offering possibilities.

[bobster]

In some cases when the piston rings are all aligned with all the gaps in the same area of the piston, it can show a low compression reading...........Did you re-torque the head down and then do a DRY and then a WET compression test ( Wet being with a squirt of oil down the plug hole) Throttle should also be held fully open when you do a compression test with all plugs removed and with a fully charged battery in good condition!

The steel head gasket should be re-usable if not damaged in any way and once you have cleaned it and given it a spray with some VHT paint........which will cure on warm up of the engine!