Topic: Seized motor question

[Tretnine]

Hey guys, I'm piecing together an idea for a story with a couple of old Hondas in it. I think one of the characters will buy a 550 with a seized motor and I'm wondering what the most common cause for a stuck motor is - blocked oil passages? Lean running conditions?

I know that you can unstick frozen motors by rocking them. What kind of damage would you be looking at? I'm guessing cylinder scoring in the affected area or possible holes in the pistons. Valve train damage if the oil passage is blocked.

Could you have a machine that runs with decent compression after it seizes? (Say if it were caused by lean running, if that's even possible)

I'm guessing minimum repairs would include new rings and honing, could possibly include valve regrind/replacement of the valve train and an overbore/new pistons.

Would a blocked oil passage on the outside of the motor (the ones by either cylinder #1 or #4) be enough to shut down a motor like this?

I'm pretty open to the thought process, so feel free to shoot out your ideas or tangential thoughts.

[MoMo]

The most common cause of seized motors is rust, which results from neglect.  I have had 3 or 4 motors that I was able to unstick and use as is, two that had to be honed, one that need to be bored and the present problem is not wanting to unseize . Have fun with the story...Larry

[Tretnine]

Thanks a bunch, Larry.

Rust might work its way in, but I was thinking of PO that had actively ruined the motor and unloaded it cheap. I suppose ruining the motor with rust would work just as well.

Anyone else have thoughts?

[cbr954]

Depends on what is "seized" in the motor.  If it was overheated could be pistons seized in bore.  If it seized from no oil it could be main bearings, rod bearings, camshaft, pistons, trans...........goes on and on.  If it is seized from sitting for years then it is most likely it has at least one piston stuck in the cylinder.  IMO if the motor is stuck  and you do get it freee, you should still take it apart to inspect and repair what is wrong or you could do more damage than what has already been done.   IMO.

[ekpent]

Had a friend once who changed his oil on an old Yamaha 750. He was a mechanic by trade. Funny thing was he got distracted doing other things and took off for a ride and guess what ?-He forgot to put the new oil in.Needed all new main bearings etc. Expensive. He will never live that down. Might be a good scenario in your story.

[MoMo]

Had a friend once who changed his oil on an old Yamaha 750. He was a mechanic by trade. Funny thing was he got distracted doing other things and took off for a ride and guess what ?-He forgot to put the new oil in.Needed all new main bearings etc. Expensive. He will never live that down. Might be a good scenario in your story.

I worked with a mechanic that did that twice to customer's bikes.  I watched and built a safe guard into my process-I remove the dipstick before draining the oil and it does not go back in until oil is added-that way if somehow the bike  was inadvertently started the noise and any residual oil would let me know real quick that there is a problem, never happened though...Larry

[Tretnine]

C

  IMO if the motor is stuck  and you do get it freee, you should still take it apart to inspect and repair what is wrong or you could do more damage than what has already been done.   IMO.

Gotta agree. That's definitely part of the story - the rebuilding of a motor, at least partially. I've rebuilt part of one myself so "write what you know" applies, but I want to make sure I'm doing things right.

Let's say the motor overheated or the oil flow to the head was blocked. How many oil passages are there to the top? Just the two?

Otherwise I like lean running conditions melting the pistons and ruining the bore. That would be a nice mix of work, but not too difficult for someone who is new (with a mentor) to tackle. Top end stuff is pretty simple, pulling the motor is a big challenge if you don't know how to do the top end already (and if you've never done anything like it.)

Ekpent, I like the idea of running with no oil, but that would involve, basically, a full rebuild, which I think is more than my character could handle. Though, it might not be a bad idea when he finishes putting the motor together to have him forget to put the oil in.

Would lean running conditions be enough to seize the motor or would it just put a hole in the pistons? What other results would that have?

[ekpent]

Some engines have seized just from overheating while running lean that I have read here. Luckily some will break free when they cool down. A piston melt down with a top end oil issue and a broken cam would be the most dramatic causing a rear wheel lock up with a small crash and a gas tank explosion     When is the book coming out ??

[bollingball]

Tretnine First off let me know if you are really writing a book or trying to figure out how you or someone else screwed up a motor and need help. If You need a book buy HondaMans it is more tech and less Oprah?. If you need help just say so

                                               Ken

[fmctm1sw]

How about a rod thrown through the bottom of the engine?   

[Tretnine]

Ken, no for real, I'm fleshing out the plan for a book. A high school grad is going to learn about honda fours from a sage adviser - but if I can't write him as the sage adviser I'm in a bit of trouble. I've screwed up plenty of things in my time (like not tightening a valve lock nut tightly enough) and would come sauntering in saying "So, I blew up a motor today..." I have no modesty, and very little honor.

How about a rod thrown through the bottom of the engine?   

This is a little intense. I'm trying to come up withe a problem that someone new to Honda's could fix (with a bunch of help.) I like the enthusiasm, though.

[LesterPiglet]

When I got my 550 the cam chain was flapping around something shocking, not long from snapping I'm sure. Sorting that problem was my first experience on a SOHC4, or any four stroke really.

I am enjoying your witterings, keep up the good work. 

[70CB750]

The most common cause of seized motors is rust, which results from neglect.  I have had 3 or 4 motors that I was able to unstick and use as is, two that had to be honed, one that need to be bored and the present problem is not wanting to unseize . Have fun with the story...Larry

The other day I was reading about using grease gun to unstuck the motor. With  adapter for the spark plug hole and cam out to make sure all valves are closed.  The way it works with brake calipers, I would give it a shot if I was in a situation like that.

[bollingball]

Tretnine That's cool I just didn't know what was really going on.
Good luck with the book. Maybe you could post a few teaser chapters here to help sales. Not sure where you should post something like this. Ask a mod.

                                      Ken

[Tretnine]

When I got my 550 the cam chain was flapping around something shocking, not long from snapping I'm sure. Sorting that problem was my first experience on a SOHC4, or any four stroke really.

I am enjoying your witterings, keep up the good work. 

Thanks a bunch, Lester, (Or Piglet, I'm not sure what your name is)

It's funny to ask such technical questions because I think in a book with global appeal I don't think I'll be writing "...and then Billy Boy loosened the bolt and slid the cam gear from the shoulder onto the camshaft proper. Later, he would be faced with the Gordian Knot impossibility of sliding that same gear back into place with the chain aligned, but for the moment - in disassembly - he didn't see the what the fuss was about, wrenching was a breeze. Only when faced with a pile of ill-sorted bolts, like some kind of jumbo Rubix cube, would he realize why he should have paid a bit more attention. This wasn't math class, you couldn't get to the end with 70% knowledge..."

Ah well.

The most common cause of seized motors is rust, which results from neglect.  I have had 3 or 4 motors that I was able to unstick and use as is, two that had to be honed, one that need to be bored and the present problem is not wanting to unseize . Have fun with the story...Larry

The other day I was reading about using grease gun to unstuck the motor. With  adapter for the spark plug hole and cam out to make sure all valves are closed.  The way it works with brake calipers, I would give it a shot if I was in a situation like that.

Cool. I've never heard of this - a lot of acetone / atf mixing, but never this.

Tretnine That's cool I just didn't know what was really going on.
Good luck with the book. Maybe you could post a few teaser chapters here to help sales. Not sure where you should post something like this. Ask a mod.

                                      Ken

I don't know. It's a sohc/4 question, but about a book. Open forum or here, it winds up in a motor discussion so I thought this was good. I don't know, at least folks here are pretty flexible.

[Duanob]

I'm not telling you how to write your story but my favorite stories on this board are the ones where a guy parked the bike 30+ years ago in a barn after a few years and very few miles of riding it. Now the motor is seized from rust and sitting and the bike is covered in dust and dirt. The new owner gets a hell of a deal on it because the engine is seized but takes it home, pours a cocktail of whatever in the plug holes, lets it sit for a couple of days, goes out rocks the engine free, does a 3000 mile tune up and carb clean, and rides the piss out of the bike for years to come. I wish that would happen to me!