Engine full of fuel and seized up

[PJM47]

Hi all,
I have a CB750K2 which was running fine, I haven't used for a few weeks and when I went to start it yesterday it turned over very slowly then the engine just locked up completely. It is now stuck solid, kickstart or rear wheel in gear won't move it. On investigation i discovered to my horror that I had what seemed like an entire tank of fuel inside the engine! I left the fuel tap on and somehow the carbs leaked into the engine and gearbox rather than come out the overflow. I have drained all the fuel and removed the plugs but the engine is still stock solid. Any ideas of what the damage might be? Is there any thing I can check to narrow it down, not sure I am up to a complete engine removal and strip down?

[Johnwebley]

Take the plugs out.

Try to turn it in reverse.

See what happens

Sent from my SM-A750FN using Tapatalk

[PJM47]

Hi, thanks for the reply. Plugs are out, tried turning it forward and reverse with the rear wheel whilst in gear and it won't budge at all.

[PJM47]

I don't think there is fuel left above the pistons now, but the engine is locked solid, like something mechanical completely jammed there is no give at all.

[K2-K6]

Cases like this have sometime resulted in bending the conrods from hydraulic locking above the piston.

Not a nice prospect,  but  a very real possibility.  Difficult to assess though without some level of dismantling,  if it's not turning with the fuel drained from it then obviously some mechanical change could have taken place.

[K2-K6]

With plugs out,  can you turn it backwards with the rear wheel?

[Nurse Julie]

I don't think the fuel in the engine has anything to do with it. The engine should still turn over but there would be a sloshing noise in the bottom end.

[Bryanj]

Unfortunately the hydro lock is most likely and you will have to remove and strip the engine to be sure

[ka-ja]

At least a "head" off and valve check.

[Bryanj]

Im fairly certain cylinders will have to come off as well to find out whats wrong

[Lobo]

...if the engine turned slowly, and then not at all, hopefully the forces involved were a gradual build versus an instant shock to the Conrods etc. Fingers crossed.

Is it possible, that fuel has pooled in the sump below the pistons and locking from below... ie have you taken the sump plug out / oil filter off to drain all fluids as the next step?

[Johnny4428]

Interesting to see if it moves with plugs out and full fluid drain, if it’s stuck still stuck then it’s full strip down.

[PJM47]

Yeah sumo drained, spark plugs out, still stuck solid, sounds pretty terminal, any ome know a good engine repairer?

[McCabe-Thiele (Ted)]

I'm gutted for you as I understand it you have had plugs out, drained the sump and its still solid - that sounds serious.
When you removed the oil filler cap did flud run out then?
Not sure from your description if you cranked the engine with the electric start or with the kickstart it needs a fair bit of pressure to bend a con rod.

I've seen flood damaged engines on Petrol & Diesel engines from when I worked at local MB dealership for 11 years - they tend to bend and often snap con rods or push them through the block as well as piston & valve damage. That said the damage was done when the engine was running. i would expect your damage to be more limited as it was done when attempting to start the engine so less force in play.

[Bryanj]

Remember Suzuki GT 250, they bent rods whent fuel tap diaphragm went and that was at kickstart speed.