Here'a a quick way to check if your engine has a bent rod due to Hydrolock. This is credited to Connierider, AKA Ted Adcock, an upstanding member of the COG community.

 First, you need to make up a quick depth guage. A long round shank screwdriver or metal rod, app 1/4" diameter works well. It needs to be at least 1 foot long. Slide a 2-3" piece of vacuum hose onto the shaft. Make sure it's tight enough to stay in the position you slide it to. If it's a bit tight, grease the rod and and the piece of hose will slide more easily.

Next, remove all the sparkplugs.

Finally, measure the piston depth of the piston PAIRS, in other words compare the height of 1-4 and then 2-3. Don't compare the 1-4 to 2-3, only compare 1 to 4, and 2 to 3. Simply drop the rod through the plug hole til it rests on the piston, then slide the tubing down til it just touches the valve cover lip. Leave the tubing in that position, go to the other piston of the pair, and drop the rod down the plug hole. The rod should hit the piston at the same time the tubing touches the valve cover lip. If one piston is low, the rubber tube will be lower comparably to the cylinder head.


    Many thanks to Connierider for offering this idea a couple years ago, and it has served me well. In light of all the hydrolocks that happen, i'd really like to see this post be a sticky. Grin Steve

Here's a vid Concours ZG1000 hydrolock rod test  Steve

Great video.  Made us of the techniques and they work.  Kept me from bending a rod.    Thanks

Great idea, I'm going to check my engine in the same way: Just went to start the bike and it locked, the engine didn't turn over, it 'knocked' hard as soon as I touched the starter, so I removed the plugs and turned it over. I small amount of fuel fired out of no. 1, the others were dry. I replaced the plugs and started it up and its running perfectly...thinking I was lucky!
The annoying thing is that I've got lots of experience with vac taps, going back to my 1980's Z650's. I checked the diaphram on this bike and it had a pin-hole in, so I replaced it using genuine K parts...and it started to leak!
The tank was on reserve, I tilted over the tank and sure enough, fuel is dripping through, about a drop every few seconds... just enough to start filling No 1. After having it running on a rigged up tank, all seems well, so I dropped it onto the sidestand, as I need to replace the balance shaft seal. lots of fuel poured out of the airbox!
I think I was pretty lucky today: the bike has been a winter project and I was going to take in for the annual MOT today, another day or two and it would have been much worse. Now I'm just about to order a petcock. 

Great idea, I'm going to check my engine in the same way: Just went to start the bike and it locked, the engine didn't turn over, it 'knocked' hard as soon as I touched the starter, so I removed the plugs and turned it over. I small amount of fuel fired out of no. 1, the others were dry. I replaced the plugs and started it up and its running perfectly...thinking I was lucky!
The annoying thing is that I've got lots of experience with vac taps, going back to my 1980's Z650's. I checked the diaphram on this bike and it had a pin-hole in, so I replaced it using genuine K parts...and it started to leak!
The tank was on reserve, I tilted over the tank and sure enough, fuel is dripping through, about a drop every few seconds... just enough to start filling No 1. After having it running on a rigged up tank, all seems well, so I dropped it onto the sidestand, as I need to replace the balance shaft seal. lots of fuel poured out of the airbox!
I think I was pretty lucky today: the bike has been a winter project and I was going to take in for the annual MOT today, another day or two and it would have been much worse. Now I'm just about to order a petcock. 

You've also got the float needle in the #1 carb that's not sealing and needs to be fixed for it to really run good.

Thanks for the reminder! I've not touched the carbs on this bike, think I'll get the MOT test passed, then strip and clean them.
Why can't we have the good old float bowls that overflowed onto the back tyre? 

Not wishing to Hijack the post, but can anyone help: I've just stripped the fuel tap, and looking carefully at the diaphram part, it has a slot on just one face of the plastic inner piece, like some sort of vent. Does this need to be fitted in a specific place (ie up/down/left/right?)
Didn't pay attention to this, maybe thats why its leaking?

Not wishing to Hijack the post, but can anyone help: I've just stripped the fuel tap, and looking carefully at the diaphram part, it has a slot on just one face of the plastic inner piece, like some sort of vent. Does this need to be fitted in a specific place (ie up/down/left/right?)
Didn't pay attention to this, maybe thats why its leaking?

Yes
It should face down when the insert is assembled...
Its a vent to atmosphere, and also a telltale weep indicator, so if diaphrgm is compromised, you will see it drip from there as an indicator.
If it was leaking from there initially, the oring on the poppet is probably shot, and now the diaphragms are warped from fuel contamination, this should be replaced. When installing the new diaphragm, as directed, prestretch the poppet spring about 1/4" or so, to insure it seals better also.

Thanks for the help: I've ordered another genuine K diaphram, its just £9.50 delivered, I was going to refit the 'new' one as its done zero hours use: it must have been dripping from the moment I fitted it, but not worth risking! I will stretch the spring as well, I'm sure that is why it leaked in the first place....

The fuel tap diaphram is fitted with the slot in the plastic spacer pointing backwards, it won't fit pointing down.

I am just waiting for the £1.48 spring as I stupidly reused the old one.....and its leaking 

This test just served me well. Long shank Phillips with vacuum tube and fender washer worked excellent.