Topic: 1978 CB400TII Hawk - Motor Seizing

[cobaltburrito]

Hi all, first post and of course it's a question.

I've got a 78 CB400T that was not running when I bought it for two hundred bucks. I've got the motor to turn over a few times by wailing away on the rotor bolt, I've even gotten it to run for about 2 seconds. Every time it I get it unstuck and run it, it locks back up. PB Blaster has been doing a pretty good job of loosening the motor up after it seizes.

So, my question is should I go ahead and pop the motor open and see what the condition is inside?

I've changed the oil and filter and the oil warning light does go out when I'm able to turn it over.

[FuZZie]

Did you find any clues in the old oil?

[cobaltburrito]

Nope, nothing that seemed out of the ordinary. Just old and sludgy.

The PO had let the bike sit outside for 4 months prior to me buying it unfortunately. I got curious and pulled the cam cover and rocker assemblies. The left side head bolts have corrosion and crud in the threads.

[cobaltburrito]

Uh oh, made a newbie mistake. I got home from work and, on a hunch, looked at the oil level. Looked pretty much dry. Only thing that I can think of is that I forgot to add oil after I pulled the starter. I may have boogered this one up real good. I've got PB Blaster in the cylinders and bought an 18 inch breaker bar. I tried unsticking it right after spraying the PB to no success. I'll try again tomorrow.

[KB02]

Yep... time to pull it open.

[cobaltburrito]

Turns out the left connecting rod is seized on the crank. Pistons, heads, cylinders, cam all look good with minimal wear. Hard to believe that a second or so of running would seize a bearing up.