Lost All Compression

Are the Pistons moving at all, may have sheared the crank. Failed compression on all cylinders at once is odd. What did it do when it stopped running, abrupt?

 

Air filter completely plugged? Can't pump it out if it can't pump it in.

 

Open throttle butterflies? Was it a k&n filter by chance? They are known for letting enough grit thru to ruin the valves and valve seats. Just trying to figure out all cylinders showing liittle compression all at once unless the inside cylinder blew out the head gasket out on both sides. Or the head warped.

 

How many miles are on it, is there any service history, particularly with regard to valve clearances?
There are 12 of the little suckers in there and with this type of valve arrangement the clearances close up over time, it only takes one out of the four in each cylinder to get to the stage where the clearance is gone and the valve doesn’t close properly leading to the valve seat burning out and no compression. The symptoms of it being harder to start 8 years ago point to this imo.

 

On ALL cylinders?

If oil has not made any appreciable difference to the leak down test my working suspicion would be be top end - worn camshaft and/or burnt exhaust valves (which would be consistent with progressively harder starting).

You will need to start at the top end anyway and look for physical signs in the valve train before taking the lid off. There is an outside chance it might be a head gasket but you would expect signs of oil/water contamination.

 

Snap! Great minds think alike..... or fools seldom differ?!

 

Sounds like a snapped cam chain to me pull the cam cover and check.

 

Id go for zero or near zero valve clearances on at least one valve per cylinder.

A friend had an FZ 750 years ago and that would start from cold everytime. Once hot no chance and it had to be bumped off. Power was good and nothing else suspicious. Once clearances were reset all good again.

Valve clearances!

 

Gummed-up piston rings? It woudn't take 8 years for that to happen! Probably worth checking anyway but I doubt it will/may be the only issue!!

From the Harbinger of Doom

 

Mermagen
Yes I would vote for the snapped camchain or the bottom cam chain sprocket snapped as they are wafer thin. Do let us all know. What was the miles on the bike. Welcome to the family
Regards
Joe

 

If the camchain had snapped then noises should be evident on cranking unless there is space for the full chain to hide. The valves wouldn't be shut as already collided but that would have previously been apparent to the rider. At least one piston should have some air above it although with no fresh incoming charge, compression will be very low but I would have expected a change in cranking tone.
If the clearances have been neglected then burnt valves are a possibility.

 

Closed up valve clearances would be my guess, maybe why it was getting more and more gutless over time

 

Just a question, how are you measuring the compression?