Took head apart - no apparent leak. What now?

I've taken off the head to more closely diagnose a cylinder with low compression. I filled the ports with water and let them sit for a few hours to see if any leaked. I also put some engine oil in each cylinder to see if it was the piston rings. I'm not inclined to suspect the gasket because there were no exterior leaks. I tried doing a compression test with a little oil in each cylinder before removing the head, but I couldn't get any conclusive result from that.

Well no apparent change in either test. I might go pick up some thinner oil because the stuff I put in the cylinders is 20w50 and may be too thick for this test.

Any tips for what to do now? What would you do if you had a motor that had 65k on the ODO and this was the first time the head was off? I bet there are more effective tests I could be doing. Any cleaning or machine work would be done by a shop because I don't have the tools or a good workspace.

 

have you put the head back on and the compression is the same? Putting oil into the barrels for a compression test fills up any gaps in the piston rings and helps them to seal. If you have done both the above and no change in compression and there was no leak by when you put oil in the head (this needs to be thin oil, thinner than 20w50 ) then the only other thing to check is your valve clearances.
Are you doing the compression test hot?
If it is a piston ring problem the oil should improve the readings. (20w50 is ok for this).
If it is your valves leaking by if you keep turning the engine ffor more tnan the three revolutions the pressure will carry on going up till it nears where it should be.
At 68k you should be thinking of a new cam chain, checking the clearances on the main bearings and big ends. The gearboox beari gs need checking too. Having said that have just stripped mine after 110k miles and was amazed how good it is.

 

Oh, yes. Forgot to mention that all the valves have been shimmed to correct specs.

I haven't put the head back on yet. The head gasket is torn in several places after removing it. I'm thinking of sending the head and the top end to a shop for cleaning, but I'm still wrapping my head around the dis-assembly and reassembly. It's an intimidating job for someone who, 5 months ago, hadn't touched a spark plug in his life and doesn't have a single gear-head buddy.

 

So on that note, can anyone suggest the cheapest way to go about de-carboning the head? I've got a cordless drill, a set of wire wheels/cups, and some plastic/brass/steel brushes.

I've heard soda blasting is a safe and cheap order for a machine shop. Should I remove the valves & exhaust gaskets before that happens or can I leave them in?

 

you can do it yourself with a soft wire wheel, that's what I did. and use a small flat head screwdriver to scrape the nooks and crannys (gently)