GS1000 head removal

[Jeff Adams]

Hey guys, is there enough clearance to remove the head on a 78 GS1000 with the motor still in the frame? All attempts to get cylinder 3 firing have failed, so I'm down to it must be mechanical.

[zed1015]

Yes there is...

[Jeff Adams]

Thanks for the info Zed.

[Nessism]

How much compression in number 3?

[Jeff Adams]

145lbs. Gas, spark, 2 thousands clearance on all valves. Makes no sense to me, so I guess the next step is pulling the head. I even swapped the intake boots around and sprayed ether everywhere. Can't think of any other diagnostics to try.

[rphillips]

With good compression, what will you be looking for when the head is off?... I'm missing something and can't remember what it is.

[Jeff Adams]

The only thing I can think of is some kind of physical damage...bent valve, cracked head? But then, wouldn't the compression be down if that were the case?

[Nessism]

If there was physical damage, the compression would be off. It's possible that something's plugged up the header pipe, but that's unlikely, because the muffler is shared.

Most likely, either a carb problem or the plug isn't firing.

[Jeff Adams]

Can't be either of those. In the original post I said there has been different plugs, carbs, and coils on that cylinder with the same result.

[1978GS750E]

"IF" you have fuel, spark and compression, "AND" they happen, when they are suppossed to happen, you should have combustion! Are you positive that both valves are opening? If the intake valve is not opening, you won't get fuel to that cylinder and no combustion happens!

Have you tried putting fuel directly into the spark plug hole and see if it fires?

[Jeff Adams]

If the valve isn't opening wouldn't that affect the compression? I have tried gas in the plug hole yet. I can try that before I pull the head.

[rphillips]

We have some strange ideas out here in the country. How about quirt some starting fluid into the vacuum access port on that carb. with one of those little plastic straws that comes on some cans of starting fluid?

[Jeff Adams]

That's an interesting idea I never thought of, think I'll try that, thanks!

[Nessism]

How about switching the coils? Move 1-4 to 2-3 and see if the problem with number 3 cylinder continues?

[Jeff Adams]

Like I said in the original post I've already swapped in another set of coils with no effect.