Topic: Engine Locked Up

[ben_jamin]

About 8 months ago, after replacing the oil in my CB550K and taking her out on a quick joy ride, the engine died on me.  And when I say died, I mean "seized" up.  After coasting off to the side of the road, I removed the oil filler cap and white smoke poured out.  The engine wouldn't turn over despite my best attempts.  Now that I have some more time (and $$$) I'm trying to figure out what went wrong. 

I removed the cylinder head and cylinder thinking the pistons had seized. Wrong.  I then pulled the crank case covers to see if I could see anything obviously wrong.  Everything appeared to be in working in order.  The clutch appeared fine as well. I turned the crank shaft with my hand and it moved the pistons fine.  I could shift through all five gears and by turning the primary shaft with my hand found that all the gears in the transmission turned fine as well.

So now I have no idea what happened and don't know what to repair!  Good or bad?  The other thing I was thinking was that perhaps something went wrong with the electric starter clutch.  Maybe it got hung up some how and righted it's self on it's own??? 

Any feedback would be much appreciated, thanks!!!   

[martino1972]

there are no marks on the pistons or cam journals etc.?

ive seen engines seize up hard,and after they cooled down they could be started again(problem not solved of cource,but to tell ya by cooling the engine off some come loose again)

did you try to turn her over just before you took her apart??

[Sporkfly]

One of my automotive teachers/professors once told me about this old Chevy he had... They ran it hard. Real hard. They would run it until it overheated and seized, let it cool down for a while and then do the same thing over. And over. And over. And she never quit, miraculously.

The point is, sometimes heat will seize an engine and it will be "fine" after it cools. How's your oil pump? Did your oil light come on when/before it seized? How do your plugs read? If you're running lean in combination with low oil pressure that would definitely cause a heat seize.

Generally heat seizes are caused by low oil pressure so it might have been caused by the fact that you just changed the oil. And of course, check out your pump.

[ben_jamin]

there are no marks on the pistons or cam journals etc.?

Nope, pistons, cylinders, and cam journals checked out nice and smooth.  Another piece of info that might be helpful: when I dropped the oil pan to view the trans gears, I found a good amount of metalic shavings in the pan!  Not a lot, but enough that I didn't have to look hard to seem em. 

The point is, sometimes heat will seize an engine and it will be "fine" after it cools. How's your oil pump? Did your oil light come on when/before it seized? How do your plugs read? If you're running lean in combination with low oil pressure that would definitely cause a heat seize.

As far as I can remember, the oil light did not come on when the engine seized up.  Haven't checked the oil pump yet; I'll take a look at that this weekend.  The top of the pistons had a significant amount of carbon build up on them, the valves also were likewise covered in the stuff.  Is this due to bad rings and/or head gaskets?

Thanks for the responses!

[Deltarider]

after replacing the oil in my CB550K...

Just the oil or did you replace the filter too? Could you've made a mistake there? But then... there is a by-pass...

I have no idea.

[ben_jamin]

Just the oil or did you replace the filter too? Could you've made a mistake there? But then... there is a by-pass...

I replaced the oil as well as the filter. 

If the pistons did seize, wouldn't I be seeing some sort of evidence of that occurring, ie marks on the pistons/cylinders??  A friend of mine has suggested that the electric-starter clutch may have some how engaged while the engine was running and thereby caused the engine to seize up on me.  This explanation some how doesn't seem right to me and it still doesn't explain the white smoke which poured out of the oil filler cap after the incident. 

Any thoughts?

Thanks.

[martino1972]

if pistons/cylinders/camshaft etc. look good....then you probably have to keep digging..
do the rods move freely??
i had an honda mt-5 moped back in the days,very heavy souped up,and it seized up on me..took cylinder off,looked perfect..
after i stripped the engine down,i found out that one off the crank bearings had seized up and spun in the case..but cold i could turn the crank freely,but i saw scuff marks in the case..
now these things dont have ball bearings on the crank,its just an example of some times you have to keep digging around to find a problem..if something did seize it will leave marks...