What a mess! Gearbox breather /oil problem must be seperate from crankcases. your first sentance says no water in coolant system ..then you say serious pre ignition problem. then you say removed the head and the crank is full of oil.... is there no piston etc.?

it could be that your head / gasket has blown & sucked water in which will not compress and therefore will lock a motor solid until something breaks which could have been flywheel key.. (maybe water even got into the primary compression/ cranckcases and blew its way into the gearbox...but thats probably fantasy/longshot where did coolant water go is first question you need to resolve....(water pump seals? head gasket?.. head cracked?) why is crancase or above piston oily ( depending on wether you removed head or head and barrel) and why did flywheel key (if it has) shear. What I'm saying is that all these symptons may be related to one incident/problem or they may not ..whatever.... it's not a good idea to put it back together without knowing why it went wrong in the first place....you just have to be methodical and eliminate the posiblities.....I think it was sherlock holmes who said something like that ..good luck keep us all posted

solved one problem removed oil and there was just about the same as i put in, there is no gearbox breather on or the little bung that sits int hole and iv been jetwashing it to the max when

returning home,

after taken the head off the bottom gasket was oily wet so that could be a blown gasket

and when i rest my parm on where the bottom gasket goes and put my fingers in the flywheel it has a twitch rock (havent a flywheel extractor yet) but not no expert with the wood ruff key but when i look down the shaft it looks like the keys still there (with nut off)

all this on one ride out

(was thinking could a little wobble on the flywheel alter my timing make it go in reverse and because i still rode it home it felt like a bag of clappers and sounded its made my gasket go) mad eh

thanks lee

after taken the head off the bottom gasket was oily wet so that could be a blown gasket

I think it is pretty confusing the way you are describing things. There is only one head gasket. I suspect you are calling the cylinder "the head". The head is the part that the spark plug screws into and it is bolted to the top of the cylinder. In between the head and the cylinder is the head gasket. Between the cylinder and the crankcases is the cylinder base gasket, or base gasket for short. The crankcase should be oily inside but the base gasket sealing surfaces should be dry.