Leak from the cylinder head?

[fishlegs]

This morning I went to fire up my Greaves Enfield, when I came to an unsettling stopping point. I went through the regular kickstarting routine, and as it didn't kick over after several trys (which seems normal on cooler mornings), I decided to try the WD-40 starting trick for the first time. I squirted a bit in, went through the kick routine... no start. The next time I gave it a full swing, instead of a chuffing engine, I was surprised by a "PFFFFFFT!" sound accompanied by a puff of vapor out the left side of the cylinder head. I did it once more for varification, and the same "pffft" and vapor came again.

Have I somehow blown the head gasket? Seems a bit odd with only 100 miles on the bike. I haven't previously seen any oil leaking from the engine and it ran great the last time I rode it. If it matters, I did just do a valve/tappet adjustment last night.

Thoughts?

thanks,
erik

[Diesel Dave]

Sounds like you have a head gasket leak - don't worry it's dead easy fix.

It's likely that the head was not torqued up tight and the cold weather overnight shrunk the alloy enough to allow the compression escape.

The head gasket is a simple copper ring so you can anneal it over the gas ring and refit.

If you don't want to strip it down then just tighten the head nuts and it will be fine; check you tappet clearances afterwards though.

It won't leak oil because the pushrod tube seals are separate to the head gasket and there's no pressure feed to the head - just vapours up the pushrod tube.

Cheers
Dave

[fishlegs]

Thanks Dave. Hopefully I'll have time to sort this out tomorrow. I can't tell you guys how much I appreciate this forum.

[fishlegs]

Finally got around to this. I was pleasantly surprised by how easy it is to pop the head off and I thoroughly enjoyed the whole endeavor, even though upon reassembly, the bike's still not starting.

In the process of lifting the head off the engine, I accidentally broke the seal of the cylinder with the lower end. So out of curiosity and to have a look at the seal, I went ahead and pulled the cylinder off as well. There's a small tear on the inside edge of the cylinder base gasket, but as I have no spare on hand, I resolved to wipe the mating surfaces clean and remount the cylinder. The base gasket measured 0.12mm thick. "Greaves 500-020-29-B" is stamped on the cylinder. Of course, I had a fine time fitting the rings back into the cylinder without a proper compressor on hand (won't happen again). I must embarassingly confess that I failed to realize that while improvising a homemade ring compressor, I did not take pains to insure that ring gaps were staggered at 180 deg and not in line with the piston pin. I will of course address this before I attempt to start up again. I removed the head gasket (measuring 0.52-0.54mm thick), annealed it, and wiped the mating surfaces. I did spot a couple small imperfections in the head gasket surface in the form of a few small bumps. Made sure the pushrod tube sat properly in its seals, checked the injector protrusion (3mm) and bumping clearance (approx 7mm). Remounted the head, torquing in the proper order to 35nm and adjusted valve lash at TDC on the compression stroke. Put everything else back together again, ready to kick start it up... AND....

no start...not even with the electric starter. Certainly a bit frustrating, but I learned quite a bit in the process and can probably do the job in 1/3 the time now. I can't however say for sure that when I kick it over I hear that same "pfft" noise as was the original symptom, but I also can't say that I don't.

-Could the non-start problem be related to the slightly torn cylinder base gasket? I want to replace it, but my parts diagrams don't depict that gasket for some reason.
-The Greaves and Lombardini manuals that I'm working from don't prescribe any sealer for the cylinder base gasket, head gasket, or push rod tube seals so I didn't put any sealant on these. Should I have? What sealants would you recommend for each?

[fishlegs]

Glad to say everything is starting and running smoothly again. I just took the top end apart again, removed the cylinder base gasket (which appears to have been made out of a soda can), and used a minimal amount of sealant in its place (minimal = http://www.gunsmoke.com/motorcycling/r100gs/sealant/). Three seperate Lombardini/Kohler sources advised that no cylinder base gasket is stocked and the conservative use of a sealant is advised. The original assembler used an unsettling amount of sealant on base gasket, head gasket and the pushrod seals! I staggered the rings this time and also fitted a thinner head gasket and replaced the pushrod tube seals (no sealants). The difference in compression is quite evident, and it kicks over well despite the cold.

[Diesel Dave]

Well done mate,

Did you measure the bump clearance?

[fishlegs]

I forgot about the soft solder trick so I used the method discussed in the manual. However, it seemed as if the piston was not entirely level in relation to the rim of the cylinder? Meaning that the bumping clearance measured smaller closer to the front of the cylinder than the rear.

[Diesel Dave]

There's allways a little difference, not to worry