Unsticking a frozen piston.

Someone on the A.T.I.S. mailing list suggested the following for unseizing pistons and it worked well for me.  I had poured a kero/diesel mixture into the stuck bores and left it for a week and then this guy suggests that I just stick some rag into the mixture, light it, and let it burn for a half hour or so.

So I did and after half an hour I engaged the starter engine and rocking it back and forth by hand, the main engine quickly came unstuck.  The theory is that firstly letting the mixture sit there for a week does a lot of good but then the heat from the fire really helps separate the stuck bits.

I tried starting it after getting the pistons un-seized but it would only fire every now and again, so I bit the bullet and decided to give the engine a bit of a touch up.

Click on the pictures below for a larger view

The pistons looked good other than a slight watermark in No.1 which rubbed out easily with wet and dry.  There are five rings per piston -  One top ring, two middle rings and two oil rings.  I re-used one oil ring and one middle ring on each piston and got new top rings, four new middle rings and four new oil rings.  The rings to be re-used were glass bead blasted to give them a new surface to bed in on.   The bores were honed and although there is a slight watermark in No.1, they will be fine.  I was amazed at how clean things in the crankcase were. The sump was full of gunk as expected but the rest of the crankcase looks good.  The big end bearings were nearly as good as new and went back in untouched. 

The injectors are have been reconditioned and I welded and re-machined the pre-combustion chambers where they were leaking.  The head's had a re-face and valve job and the water pump's had a new rear bush and packing.

One thing I pondered for a while was the problem of the water seal between the diesel head and the pony.  I was told that the o-ring that goes there is no longer available so I got an o-ring of the same cross section, cut it with a sharp knife in one spot and carefully glued it into the groove in the pony motor with super glue. See the photo above - right.

The head went on with no problems and the o-ring replacement sealed fine.   After a bit of mucking around that can occur when first starting a rebuilt motor, it finally ran (third photo above) on it's own for the first time in who knows how long.  It had a few minor water and oil leaks that were easily fixed and it now starts and runs very well.