Hydrolock

Terry · Post by **Terry** » Thu Jul 30, 2009 3:35 pm

Since Larry's thread came up I thought some of us might need a refresher. This deals with water (mostly) but any liquid is not very compressable so the theory is similar. Question though, wouldn't turning over the motor with the kill switch in the off position prevent hydrolock and engine damage? Even if the cylinder was full of liquid, there would be no fire to ignite it. Comments?

http://en.wikipedia.org/wiki/Hydrolock

CBXRoger · Post by **CBXRoger** » Thu Jul 30, 2009 3:54 pm

No, hydrolock will occur with just turning the engine over with the starter. There are many '79's with a broken crankcase and number one rod protruding. Liquids do not compress.

IMHO,

Roger

Don #6141 · Post by **Don #6141** » Thu Jul 30, 2009 4:05 pm

I've been told by more than one knowledgeable CBX mechanic that the starter motor alone doesn't have the power to do any serious damage and that bent rods and the like are the result of one or more cylinders firing before the wet cylinder comes to TDC on the compression stroke

Based on this, if there's any question at all (like when I put it on the sidestand and forget to turn off the fuel) I do just as you suggested Terry and turn off the kill switch before attempting to start it

Don

alimey4u2 · Post by **alimey4u2** » Thu Jul 30, 2009 4:21 pm

OK not a real test as my rods are OMT but I have had # 1 hydrolock just turning the starter motor ( ignition off) without any measured effect. Popped the plugs, measured the stroke with a DTI on an extension & no difference in piston height at TDC...
I then pulled all the plugs & ran the motor on the starter to clear, squirted oil through the plugholes. Span it again & replaced the plugs... Changed oil & filter..Good to go...

FalldownPhil · Post by **FalldownPhil** » Thu Jul 30, 2009 10:06 pm

Speaking from personal experience. Don#6141 is correct. The starter motor alone with no fire will not bend a rod. I had this experience a few years ago. If ever there is any question about the possibility of a cylinder with fuel in it I will crank the engine with the switch in the off position. I did this on a suspect system and had the engine stop dead in its tracks. I am sure that if the switch had been in the run position, it would have fired on another cylinder and bent a rod. Instead, I pulled the plugs and cranked it around a few times. All is well that ends well.
Very Best,
Phil

alimey4u2 · Post by **alimey4u2** » Fri Jul 31, 2009 4:07 am

Maybe one benefit of having a poor charging system is a weak battery...

One thing I may advise, don't smoke when your clearing the cylinders of gas ( spinning the motor.) In fact, ignition off ( very important) put a towel over the cylinder head if you don't want your paint damaged...