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Was I incorrect in what I'd figured about ratios and PSI's?

Thing is I couldn't find in my Haynes specs what the desired PSI is for the LC. Its perfectly possible I've gotten mixed up in my calaculation attempts

Thing is, disregarding the above and sticking with PSI's, I'm not convinced that the compression gauge I used is functioning correctly.

Each crank, the gauge would bump up to around 60PSI. Then, as soon as the kick start pressure passed, the meter would drop back down to 0. It wouldn't stick there so it could get bumped up a little bit more at the next kick. From what I understand, for this to happen, the bike would have to be pretty much a dead-knackered-heap with a seriously major compression leak/problem somewhere, and there's no way it would even start no matter run pretty well at speed!

Any thoughts?

I haven't taken the bike out since the head nut tightening, I need to run it around and around so the engine gets nice and hot to see what happens - while staying close to home in case we have cut out again.

you need 70 pounds of compression for it to even start.
i dont know what kind of compression tester you are using but a decent one has a release valve on it.you get the engine hot then check the compression.if you are using a kick starter you kick 7 times then read tester. then push the release valve. the engine cant hold compression after you quit cranking it.you need to hold the throttle wide open when checking compression.

9000white wrote:you need 70 pounds of compression for it to even start.
i dont know what kind of compression tester you are using but a decent one has a release valve on it

Thats what I thought - and the bike starts really well (when cold at least amyway) on the first kick usually, if not then the second.
The tester does have a release button which is meant to reset it back to zero - but when I've been using it, its been going up with the kick - then dropping immediately flat back down to 0, not holding the reading

the release valve aint working .
they have a little o ring on them that dries out and cracks.

You just over-complicated the process, that's all. No biggie. The PSI reading on the gauge is all you need to know.

Whitey is right, your gauge is pooched, well actually the valve core in the hose fitting is pooched. It's just a tire core valve, easily found at an autoparts store. I use ones that have teflon seals to take heat better, but I test on hot engines only. Regular valve stem cores will work. The valves still fail every 6 months like clockwork. Easy to change out though.

If possible, get the engine up to running temp and whip out the plug and test it as fast as feasible. As for method, there's lots of procedures floating around. Don't pay attention to any of them. Crank/kick it over until the guage reaches it's highest reading. This will happen a few revolutions sooner if the throttle is held open, but it will reach the same reading even with the throttle closed.

Your still filling the cylinder with fuel/air, so turn the ignition or run switch to off, so the plugwire don't flick sparks at everything.

Do I just unscrew something to replace this?

you will need a valve core remover.auto parts stores have them and the new cores too.

Well I never did get the replacement valve. What I did do though, was start the bike up and warm it right up. About 1/3 on the temp gauge. Then rev it up and hold it at about 6k, then let go and let it drop right down to see if it would fade away and cut out.. which it didn't! Each time it just fell down to 1400 and ticked over.. no spluttering, popping, or dying. I switched it off a few times too, left it for a few minutes and then tried to start it up again - which it did first kick.

I did try to use a paddock stand to rev it on and engage the gears, but it wasn't safe (suprisingly, seeing as its not designed for that ). So tomorrow we'll see how it does using the gears. Hopefully, it will be no different, and it'll work happily Fingers crossed!

if all goes well tomorrow then just ride it and it will be happy.

Take your compression gauge to the nearest mechanic. Look sweet and demure and bat your eyelashes alot. I promise he will not only give a new valve, he will change it out for you too.

It also works on female mechanics, but if she offers more 'extra free services' on top of the new valve, you might want to beat feet back outta there in a hurry.