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Discussion Starter · #1 ·
Hey,
I have an '81 750 Honda that was running when I leaned it up against the hedge bush. It has set there and froze up. I tried wd in the plug holes and rocking the wheel in gear and it won't budge.
Is there something that would work better for breaking down the corrosion I know has to be locking those pistons? short of tearing the top end down??
 

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Depends on the kind of time, tools and work area you have available, but "if it were me," ......I could see myself tearing the motor down and refurbing piece by piece.

-Soupy
 

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http://www.autozone.com/greases-and...se/crc-freeze-off-super-penetrant/898352_0_0/


I am always looking for the best I can find. I used to think that Kroil by Kano Industries cannot be beat, but the Freeze-off is at least as good and sometimes better, and you can buy it everywhere. I spray down the entire fastener array on any bike before I remove parts. Do not breathe the fumes in an enclosed area as they are nasty

If there is any way that you could absorb the WD40 out of the pistons,it might be a good thing to do. Wd-40 is like nothing compared to this stuff and might water down its performance.
 

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I have restored quite a few pieces of antique machinery and the best I have found is #1 Stove Oil (heating oil). If you can't find that, diesel fuel works almost as good. Both are better than any penetrating oil on the market (and cheaper too!)
 

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"I leaned it up against the hedge bush."

How long on the Hedge bush??

Were the sparkplugs out or the intakes uncovered??

Somehow, make sure you have it in neutral or remove the drive chain.

Does a 1981 CB750 have a kickstart lever or is it just electric?

Rarely does an engine completely seize up unless it was one of my 2 stroke track bikes.:mad:

Sam:):coffeescreen:
 

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Discussion Starter · #6 ·
"I leaned it up against the hedge bush."

How long on the Hedge bush??

Were the sparkplugs out or the intakes uncovered??

Somehow, make sure you have it in neutral or remove the drive chain.

Does a 1981 CB750 have a kickstart lever or is it just electric?

Rarely does an engine completely seize up unless it was one of my 2 stroke track bikes.:mad:

Sam:):coffeescreen:
Long enough for the wire it is tied up with to grow into the tree. The plugs were in and tight and the carbs are in place but no breather covers. I am sure it got moisture into at least one or some of the cylinders since some of the valves were probably open. It does not have a kicker. I can put it in any gear. That is not the problem. I was rocking the back wheel with it in gear to try and jar the engine loose. The starter won't budge it. It does, however, engage and seems as if it would work if the engine wasn't frozen.
 

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I'm guessing you're going to have to ultimately take it apart to fully clean up any **** that's holding the pistons in place.. think if it as the price to pay for "quick storage"

You'll probably at LEAST need to pop off a side case cover so you can try turning over the engine using a breaker bar at the crankshaft, but do so at your own risk
 

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You are in store for a complete top end rebuild due to the intake being open and rain, snow and moisture getting in, rolling through the open valves, onto the top of the pistons and rusting everything from the intake. exhaust valves, valve guides, rings against the cylinders etc. Lots of these aforementioned parts can probably be cleaned up and used again if need be. The moisture also made it's way into the carb bodies, passages and float bowls so those things will be corroded.

Pray that once the top end is completely removed that the rods and crankshaft are rust free---if not, it all has to be rebuilt.

If it's a labor of love and you have the expertise and tools to do it as a long term project, go for it. It would probably be fun.

However, nice, running CB750 are available all over the world wide web and some are very cheap.

I had a new 1974 CB750 and a new 1976 CB750A, the auto trans one! They were great bikes.

Sam:):coffeescreen:
 

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Discussion Starter · #9 ·
Yeah, it was one of more stupider blunders. I got the bike for a song and it ran great. 4n21 and all loud. I rode it up to the tree it is still leaning on and it was not long at all that I realized it had seized up.
I had planned to make a scaled down Honda powered rail buggy. I think I would have beat polaris to it by a few years.
I could imagine a manual five speed high powered go cart with a full cage and posi-traction rear. Talk about a drifter in the gravel!!!
 

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diesel fuel in the cylinder and use compressed air to try and move the piston. Rock it back and forth hard enough and you can trash the transmission.
 

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I've never had any luck breaking a froze engine free and I think it would be junk even if you did. I tried to break a frozen pickup engine free just to drive it to the wrecking yard. I pored cutting oil on the pistons and put in high and puled it a bit with a car, all I did was break a rod.
 

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I have restored quite a few pieces of antique machinery and the best I have found is #1 Stove Oil (heating oil). If you can't find that, diesel fuel works almost as good. Both are better than any penetrating oil on the market (and cheaper too!)
I did exactly this on a bike I bought for $50. filled each cylinder about half way with diesel fuel and let it sit for a month, more because I was busy than being patient. I turned the engine over several times with the plugs out to get the excess fuel out, then fogged it with WD. I had cleaned the tank prior to trying to start it and filled it fresh gas. I had it running inside of an hour, lots of smoke!
Good luck and dont force it.

BTW I sold it for $850.00 6 months later!
 

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Discussion Starter · #13 ·
Ha, my son bought a 125 elsinore that was seized up for $15. We put some kind of lube or other in the cylinder and got it freed up and running that night. He sold it for $125 the next night. Wish this one would work out that way. I think I will try filling the jugs up with some penetrant or oil or other and see if anything want to move in a couple of weeks. I might fab up an adaptor to connect a hydrolic pump to the plug hole. Oops that won't work if the valves are open. back to the drawing board.
 

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http://www.autozone.com/greases-and...se/crc-freeze-off-super-penetrant/898352_0_0/


I am always looking for the best I can find. I used to think that Kroil by Kano Industries cannot be beat, but the Freeze-off is at least as good and sometimes better, and you can buy it everywhere. I spray down the entire fastener array on any bike before I remove parts. Do not breathe the fumes in an enclosed area as they are nasty

If there is any way that you could absorb the WD40 out of the pistons,it might be a good thing to do. Wd-40 is like nothing compared to this stuff and might water down its performance.
I agree, that freeze off is the best. Used to use PB Blaster alot, but that Freeze Off works even better. Rusty stuck nut? Spray and let it sit, and no more knuckle busters....
 

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If you actually want to keep the bike and use it, start by stripping the engine down (if you can) and remove the pistons from the bore once the cylinders are off the bike - you will need to anyway to replace rings and at least hone the cylinder, if not re-bore it to the next size up.

A decade ago I restored a little bulldozer that had sat for 20 years and the pistons were so badly seized that I had to break them up with a steel bar and a sledge hammer! Bored 0.060" over-size, new rings and pistons, and that little machine is still running great.
 

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"I leaned it up against the hedge bush."

How long on the Hedge bush??

Were the sparkplugs out or the intakes uncovered??

Somehow, make sure you have it in neutral or remove the drive chain.

Does a 1981 CB750 have a kickstart lever or is it just electric?

Rarely does an engine completely seize up unless it was one of my 2 stroke track bikes.:mad:

Sam:):coffeescreen:

+1 I agree with Porky!
I retrieved a Kawasaki '75 Z1-B 900 from a barn where it had sat for over 20 years...it seemed nothing would move...BUT, when I finally got the chain off....engine was fine, the Chain and everything else made it seem engine was locked up if that makes sense??.As others have stated, if it is engine, remove spark plugs and generously pour Krill Oil, or Marvel Mystery Oil in each cylinder, allow to sit and gently try to get engine to turn over....sometimes it takes a little time for engines to free up. Oh yea! I see you are from Cleveland,TN.?? Thats not too far from me , I live in "Seymour", TN. ( Sevier Co.)
Anyway, Good Luck and hope to see posts with updates if you have time.
Regards
Ed
 

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I ride to see a High School buddy that lives in Ooltewah,TN almost every year and I highly recommend TN to anyone that loves beautiful scenery and great roads.

Two stroke bikes have so much oil around their piston(s) and cylinders that they will rarely be rusted up if the sparkplug and intake filters are intact.

Sam:coffeescreen:
 

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Discussion Starter · #18 ·
+1 I agree with Porky!
I retrieved a Kawasaki '75 Z1-B 900 from a barn where it had sat for over 20 years...it seemed nothing would move...BUT, when I finally got the chain off....engine was fine, the Chain and everything else made it seem engine was locked up if that makes sense??.As others have stated, if it is engine, remove spark plugs and generously pour Krill Oil, or Marvel Mystery Oil in each cylinder, allow to sit and gently try to get engine to turn over....sometimes it takes a little time for engines to free up. Oh yea! I see you are from Cleveland,TN.?? Thats not too far from me , I live in "Seymour", TN. ( Sevier Co.)
Anyway, Good Luck and hope to see posts with updates if you have time.
Regards
Ed
The chain is rusted but I had the side cover off the engine and bent a large screw driver trying to turn the fly wheel. She is stuck. I did put something in the cylinders, can't recall what now.
I hung out around Gatlinburg some. My old lady was manager at the tb when we got tangled up.
What about that Kawa? I had the pleasure of riding a '72 Z-1 that had everything Pops Yoshimura made in it. I'm talking 80+ in first gear. The second time I took off (after I was out of sight of the owner) I yocked it and it almost left me standing there. I learned real quick to take a hold of the reigns tightly. Since that day I have wanted to own one like it.
 

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The chain is rusted but I had the side cover off the engine and bent a large screw driver trying to turn the fly wheel. She is stuck. I did put something in the cylinders, can't recall what now.
I hung out around Gatlinburg some. My old lady was manager at the tb when we got tangled up.
What about that Kawa? I had the pleasure of riding a '72 Z-1 that had everything Pops Yoshimura made in it. I'm talking 80+ in first gear. The second time I took off (after I was out of sight of the owner) I yocked it and it almost left me standing there. I learned real quick to take a hold of the reigns tightly. Since that day I have wanted to own one like it.
I am going to attempt to attach pics of before and after of the "Z" which I called Jonah,,as in brought back. The "Z" is Still Wicked fast even after 40 years!
Ed
 

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