Freeing a Siezed Motor

[canuck750]

I have bit the bullet and bought another old Italian motorcycle in need of a full rebuild, this time its a 650 Benelli Tornado, only because it's Italian and the same vintage as my other bikes and I have a soft spot for the weird and quirky.

The engine is reported to be seized solid.

I read once that filling the crank case and cylinders up with diesel fuel will sometimes free the engine??

Any advice on what is the safest means of trying to free up a motor?

I will eventually strip the engine down but I would like to get in 'un-stuck'.

Thanks

Jim

[troyhamilton]

2 things ive done. 50/50 acetone and trans fluid. and ive used coca cola. the acid eats rust!

[canuck750]

2 things ive done. 50/50 acetone and trans fluid. and ive used coca cola. the acid eats rust!

I heard about the acetone and transmission fluid before, good results?

[oldbike54]

 Depends on how bad it is stuck . Years ago an old BSA motor was dropped off at my house as a thank you for rebuilding a different old BSA motor . After Diesel fuel , acetone, heat , cold , and a dead chicken were employed , it came down to a cutting torch and sledge hammer . Try the 50/50 mix advised earlier first , that old BSA motor was reduced to scrap , but I won 

 Dusty

[Rough Edge racing]

  So it's an engine that was running and then shut off and sat for a time and set up... Not a running engine that seized because it was severely overheated and or run without oil?

[webmost]

PB Blaster in the spark plug hole.

[guzzisteve]

I would pull the head off 1st and have a look see.

[troyhamilton]

after its soaked a few weeks, put it in high gear, rock the back wheel back and forth. sometimes a blind pig gets luck.

[twowings]

Marvel Mystery Oil in each plug hole...let simmer for 2-3 days, then turn over by hand...

[siabeid]

     I got the "fence post" unseized by squirting a lot of Moovit into the spark plug hole several times for a couple weeks. I then used a prybar on the flywheel through the timing hole and it popped loose. I have had pretty good luck a couple other times by squirting Marvel Mystery oil onto the piston for a couple weeks and then breaking it loose with the rear wheel like troyhamilton suggested or using the kick start if it had one. There was only one time that I have encountered where it wouldn't come loose. That was on a r75/5. I had to use a puller to pull the cylinder off the piston. It made a mess of the top of the piston, but it and the cylinder were junk anyway.

[troyhamilton]

my grandfather once made a grease zirk fitting in a plug hole, pulled the rest of the plugs. filled it with grease, used a presurized grease gun and broke it lose. id be afraid of bending a rod in that instance

[Guzzidad]

   I've tried the acitone and trans mix, PB Blaster, etc, etc. I like Marvel Mystery oil. But by far, the best penetrating oil I have ever used is Knock Er Loose by CRG.

[guzzista]

One of my Benelli Tornado projects had a stuck motor. Removed the heads and as luck would have,there was some room on top  as the pistons were stopped about an inch and change from the top. Soaked in diesel for about a week tapping lightly on the pistons with a wood block every so often. Eventually they loosened up. Good luck, Jim

[canuck750]

Thanks for all the good advice guys!!, I have been lucky to never had a stuck motor.

The Benelli should arrive in a week or two and then I will start the soaking process.

Jim

[Muzz]

Only ever done it (once) with the head off. Penetrating oil for a considerable period off time, then whaked it with the wood and hammer after a bit of heat to the barrel.

[pete roper]

Well first you have to establish what has seized surely?

[Aaron D.]

Funny, when this project is finished it may be the nicest on the planet!

On the centerstand, these bikes will walk around wile idling if parked on concrete, sort of like an old '60s toy football team.

[pauldaytona]

Funny, when this project is finished it may be the nicest on the planet!

On the centerstand, these bikes will walk around wile idling if parked on concrete, sort of like an old '60s toy football team.

 Just what I remember from an Laverda sf 750.

[Groover]

In the R/C Hobby days, a 50/50 marvel mystery oil and transmission fluid is what we used to prevent and loosen already seized and gunked-up engines.

These days, I'd probably pour some of this in and probably get better results.

https://www.napaonline.com/p/MCR6402

[Antietam Classic Cycle]

Well first you have to establish what has seized surely?

This, and how it has seized. I worked on a BMW /5 once that was seized due to the carbs overflowing, flooding the cylinders and then evaporating. I assumed it had rusted stuck. All of the "usual" concoctions did nothing, it wasn't until I switched to Berkebile 2+2 Gum Cutter that I started making progress.

[blackcat]

My brother in law collects and restores hit and miss engines and he has used all the above to free up a frozen piston. He did get one that just wouldn't break loose, so the word in that community is to start a fire in the hopper to break the piston loose. I'm not suggesting anything like that in this case but it is interesting what people come up with to make things work.

[canuck750]

Thanks again for the tips, I have no idea what the condition of the bike is other than it is described as the engine being stuck.

I am going to let it soak for a while and then start to pull the engine apart, looks like it will be interesting to learn how Benelli approached a twin cylinder engine. I like that the Benelli has a horizontal split crank case, like the Yamaha two strokes I used to fiddle with it sure makes engine work a lot easier!

I have found a service manual and a parts diagram so that's enough to be dangerous

[Antietam Classic Cycle]

Thanks again for the tips, I have no idea what the condition of the bike is other than it is described as the engine being stuck.

I am going to let it soak for a while and then start to pull the engine apart, looks like it will be interesting to learn how Benelli approached a twin cylinder engine. I like that the Benelli has a horizontal split crank case, like the Yamaha two strokes I used to fiddle with it sure makes engine work a lot easier!

I have found a service manual and a parts diagram so that's enough to be dangerous

I only had the top end apart on the one I owned back around '96. Over all a simple machine and much will be familiar to anyone with a Tonti Guzzi. Setting the timing was fun though - you have to remove the alternator and attach a degree wheel. This was just after mine arrived, before I started work on it:



 

There's a possibility another may come my way later this year.

[Groover]

Those things look pretty stout. Nice.

[oldbike54]

Funny, when this project is finished it may be the nicest on the planet!

On the centerstand, these bikes will walk around wile idling if parked on concrete, sort of like an old '60s toy football team.

 The old vert twin 360 degree crankshaft Brit bikes would walk backwards while idling on the centerstand . Norton Commandos would almost dance the front tire off the pavement at idle , the isolastics were tuned to work at 2,000 RPMs and above . Lots of fun to be had there 

 Dusty

[Don G]

The old mechanic in the One Horse town in which I live, freed up a flathead Ford engine that had severely rusted cylinders, I mean all 8, sitting for decades out side in the weather. He simply filled the cylinders up with water after the heads were removed of course, let it sit a couple of weeks and then started whacking each piston crown with a chunk of fence post and a 5 LB hammer, a little rocking action on the crank at the same time and success was had. He reasoned that rust was caused by water and water will penetrate the rust bond, well it worked!  DonG

[canuck750]

The old mechanic in the One Horse town in which I live, freed up a flathead Ford engine that had severely rusted cylinders, I mean all 8, sitting for decades out side in the weather. He simply filled the cylinders up with water after the heads were removed of course, let it sit a couple of weeks and then started whacking each piston crown with a chunk of fence post and a 5 LB hammer, a little rocking action on the crank at the same time and success was had. He reasoned that rust was caused by water and water will penetrate the rust bond, well it worked!  DonG

Now there's a testament to the ruggedness of a flat head Ford!

[speedyg]

I heard about this solution second hand. Not sure of the exact conditions but....
Pour oil into heads. Put engine on a hot plate, and allow the engine to warm up. Once up to temperature, 160-190F say, try working the crank every so often until the pistons release.

[RANDM]

The old mechanic in the One Horse town in which I live, freed up a flathead Ford engine that had severely rusted cylinders, I mean all 8, sitting for decades out side in the weather. He simply filled the cylinders up with water after the heads were removed of course, let it sit a couple of weeks and then started whacking each piston crown with a chunk of fence post and a 5 LB hammer, a little rocking action on the crank at the same time and success was had. He reasoned that rust was caused by water and water will penetrate the rust bond, well it worked!  DonG

That's what I used on a B33 BSA that had been sitting
Outside without a Carby or Exhaust Pipe for a couple
of years. At 19 and with no-one to advise me it was all I
could think of - I think I was lucky as I didn't use any
lubricant.

Maurie.

[Triple Jim]

I had a seized engine that just had the rings a little stuck to the cylinders with light rust.  The engine wouldn't turn, but all it took was tapping on the pistons with a wooden handle of a hammer.  It ran for quite a few miles after that before I redid its top end.