Stuck Motor?

Posted: Mon Aug 17, 2015 1:30 am

Just picked up my first Honda Cb, 82 Honda CB900 Custom. 160 bucks off an old friend. brought it home and tried to jump the solenoid. a few bumps but not turning over the motor. So i wasn't convinced or mostly didn't want to believe it so i tried to spin it it over by the crankshaft. was able to spin the motor about half a revolution very easily before it stopped. pistons are all moving up and down. no spark plugs in or carbs connected. can here compression strokes. bike sat for a long time with carbs detached outside, valves show surface rust. sprayed a lot of penetrating oil on them and it came right off. What do you guys think? Rolling Eyes

Posted: Mon Aug 17, 2015 1:46 am

Cam chain in good shape? Possible debris in the cam tunnel? Expect to split the cases to get the answer...

Posted: Mon Aug 17, 2015 1:54 am

Put oil into the cylinders and let sit. Try again after 24 hours. Could be rust on the rings sticking on the cylinder walls.

Posted: Mon Aug 17, 2015 2:04 am

I've used Marvel Mystery Oil in the past. Fill up the cylinders and let sit for 24-48 hours. Check it in 24 and if still stuck try putting some more in the cylinders. Also PB blaster will cut through rust quickly. Spray some in the spark plug holes and be generious when you do it.

Posted: Mon Aug 17, 2015 2:13 am

BlueThunder wrote:

Put oil into the cylinders and let sit. Try again after 24 hours. Could be rust on the rings sticking on the cylinder walls.

750rider wrote:

I've used Marvel Mystery Oil in the past. Fill up the cylinders and let sit for 24-48 hours. Check it in 24 and if still stuck try putting some more in the cylinders. Also PB blaster will cut through rust quickly. Spray some in the spark plug holes and be generious when you do it.

Even if this worked (and yes, it would be good news) I wonder if the motor would be a runner without a rebuild? Has anyone done this with an engine and gotten a smooth running, reliable engine as a result?

Posted: Mon Aug 17, 2015 2:28 am

You got it from an old friend, was it running when he parked it??? If not I'm thinking the long cam chain. But regardless you're looking at splitting the cases to get it running anyway so you may as well start with the valve cover and see what the cam chains are like.

Posted: Mon Aug 17, 2015 2:52 am

cliffiec wrote:

BlueThunder wrote:

Put oil into the cylinders and let sit. Try again after 24 hours. Could be rust on the rings sticking on the cylinder walls.

750rider wrote:

I've used Marvel Mystery Oil in the past. Fill up the cylinders and let sit for 24-48 hours. Check it in 24 and if still stuck try putting some more in the cylinders. Also PB blaster will cut through rust quickly. Spray some in the spark plug holes and be generious when you do it.

Even if this worked (and yes, it would be good news) I wonder if the motor would be a runner without a rebuild? Has anyone done this with an engine and gotten a smooth running, reliable engine as a result?

Only a riding tractor lawn mower. My ex-father-in-law left one outside for 7 years. Same issue in that the motor would not turn over - being "stuck". Put motor oil in the cylinders for 36 hours, turned over by hand. I figured what the hell, changed the oil & filter, gave it a tuneup and WHAMO!! The thing started, smoke a lot ( Very Happy

). Its running fine after 15 years! Would I do it for a bike? Probably not....

Posted: Mon Aug 17, 2015 4:20 am

Thank you for the responses. Friend i bought it from has only had it for a few months. I'm way ahead of you guys, oil is sitting in there now before i did that i emptied half a can of PB blaster on the valves and cylinders. Fingers crossed, one detail i forgot to mention however. When i removed 3 spark plugs they all looked good. but when i removed the last one the electrode was smashed, and the plug was wet with water and rust. put a long 1/4 inch extension through the spark plug hole, and spun the engine over as far as i could and it moves up and down its full stroke as far as i could tell.

Posted: Mon Aug 17, 2015 1:10 pm

Stuck valves will do this too. Not uncommon if its been sitting for a long period, especially if left in a shed or unheated garage.

(Valves open, piston comes up and strikes valves, stops rotation.) (or any other debris in the combustion chamber).

Posted: Mon Aug 17, 2015 1:38 pm

Wayne750F wrote:

You got it from an old friend, was it running when he parked it???

Was there ever one that wasn't? Smile

Posted: Mon Aug 17, 2015 1:49 pm

i will let them soak longer. may end up just pulling engine and going through the head.

Posted: Mon Aug 17, 2015 5:19 pm

Hahaha well Glen, an old friend should be trustworthy I would hope!!!!! But other than that? No they were all running when parked....

Posted: Mon Aug 17, 2015 9:29 pm

he offered me my money back, he had bought it in the same condition just a few months back never has looked at it

Posted: Mon Aug 17, 2015 10:19 pm

I think you got a steal! You can rebuild that thing to it's former glory and beyond, if you have the time, patience, and desire!

Posted: Mon Aug 17, 2015 10:32 pm

Right on Cliff!!!! Like this old girl that's headed to 887......

That's what we do!!!!

Posted: Mon Aug 17, 2015 11:24 pm

You don't get much for $160, fix it up,craigslist, or part it out

Posted: Wed Aug 19, 2015 12:17 am

Pulled the motor today, took 2 hours by myself. not bad for my first time working on a bike. Now that I'm at this point, i don't know if i should do a rebuild, or buy a used running motor. How much can you guys rebuild these for?

Posted: Fri Aug 21, 2015 1:11 am

'...bike sat for a long time with carbs detached outside...'

'... the plug was wet with water and rust.'

Death knell.

While engines can often be pulled back from the edge, I have generally never seen one like that do so. If water got inside the cylinder and sat, the cylinder walls and/or combustion chambers are junk. Also, between oil and possible water, if you hydrolock a cylinder, any extra effort trying to turn will bend or break parts.

Luck.............

Posted: Fri Aug 21, 2015 2:13 pm

soates4 wrote:

Pulled the motor today, took 2 hours by myself. not bad for my first time working on a bike. Now that I'm at this point, i don't know if i should do a rebuild, or buy a used running motor. How much can you guys rebuild these for?

Just start with the top end and make a decisions from there.

Posted: Fri Aug 21, 2015 6:12 pm

Shawn_Mc wrote:

soates4 wrote:

Pulled the motor today, took 2 hours by myself. not bad for my first time working on a bike. Now that I'm at this point, i don't know if i should do a rebuild, or buy a used running motor. How much can you guys rebuild these for?

Just start with the top end and make a decisions from there.

What Shawn says.... If the cylinder walls look good, then just do a top end rebuild... Clean head, verify valves are not bent, lap valves in and replace with 16 new Viton valve seals from member, Genesound..

My guess though, if the crank does NOT spin around like you mentioned, there is much more "stuff" that is bad.... But we won't know until you take it apart...

Post pics and ask questions here, we will have the answers..

Posted: Sat Aug 22, 2015 5:54 pm

pulled the head to find about an inch of mud inside cylinder 1. sweet. not wanting to rebuild, but do want to source another engine. if anyone has one let me know! also if anyone needs any parts. will be parting out.