Stuck Motor

[Mike OReilly]

You would think with all of the old, neglected Pentons out there, some being discovered as time goes on, that this topic would have come up; I don't recall ever reading about this here, and a search didn't turn up anything.

So here is my question:

What tips/techniques do you all have in regard to dealing with a motor that is well and truly stuck after many, many years of storage and neglect? Basically aluminium bonded to steel.

Preferably without destroying the piston.

My experience leads me to believe that heat (propane? oxy/acetalyne?) would be involved in some way.

Any and all tips would be greatly appreciated before I blunder off on my own.

Mike

[454MRW]

I'm sure there are a lot of good suggestions out there, but I have heard that the best penetrating fluid is a 50/50 mixture of ATF and acetone. Filling the cylinder, (or as much as possible considering open ports), with a mixture of that would be a logical first step, and could be used even to the extent of filling the crankcase. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Penton
1976 MC5 400
1978 KTM 78 GS6 250
L78-79 MX6 175-250 KTM's
1976-78 125-400 RM's
2007 CR125R Honda
1977 MC250 Maico
2017 KTM Freeride 250R

[johnborn]

i have never had to deal with this but i don't think you would want to use a lot of heat on an aluminum casting. with something like this patience is the most important tool in you toolbox.

[Daniel P. McEntee]

First, you have to understand just what you are dealing with. Pull the exhaust and carb, (and maybe the head) and take a gander in both holes and see what you find. If you see any damage to the piston, proceed with caution but no need to try and save a broken piston, you just don't want to mess up the cylinder..
 You most likely won't have aluminum bonded to steel, but will have iron piston rings rusted to the iron liner. Soaking with lots of oil is a start. Heating to as near operating temps as you can, and letting it cool, will expand and contract the cylinder and help work it loose. Take a stab at the kicker every now and then. Some guys put the bike in gear and rock it back and forth. I got one loose once by removing the head for inspection also, and gently tapped on the piston with a small mallet and a wood block. Not 'beating " on it, just repetitive knocks that do more good. Check frequently for movement during all of this. If the bottom end is loose at all, you will get it to break loose if it wasn't seriously seized in the first place, and that was the reason it was parked. As has already been said, patience is the virtue here.
  Type at you later,
   Dan McEntee

[Paul Danik]

Hi Mike,

   On a stuck Sachs I would also recommend taking the ignition sidecover off and seeing if there is any movement of the ignition flywheel, helping you to evaluate if the engine is stuck on top or in the lower end.

   Not sure what others will think of this...but one of my favorite tools is a set of chain vise grips. I have used chain vise grips numerous times over the years to slowly break loose a stuck top end. The chain can be wrapped around the flywheel and then lock the visegrip providing grip around much of the flywheel, and now giving you a way to slowly "work" the top end. Care must be taken as you lock the vise grip to not over tighten it and possibly damaging the flywheel. In all my years of doing this I have never damaged a flywheel, even Bosch with magnets, just try to grip the flywheel near the front, not towards the back where you might flex the flywheel and loosen or crack the magnets.

  This method may work on other engines as well, but my experience is just with the Sachs.

Hope this helps.
Paul

[JamesHorwatt]

Rest assured,stuck engines can be intimating. I've unstuck a few in the past using various methods. From using a home-brew of WD 40/and ATF, to rocking the bike in gear to using a hot plate placed directly under the engine. Think about about it for a moment...the engine was hot the last time it ran,and all the internals were expanded. So why not try and create the same scenario again ?. Good Luck and hopefully the engine God's are looking down on you.

Jim Horwatt

Thanks Jim