O.S. Engines FR5-300 Sirius partial teardown
This may be a redundant thread on this engine, but I thought I'd walk-thru my efforts to free up the subject radial engine. It had been stored improperly and was fully gummed up to the point where no movement was possible. There are pics here of the reassembly, which may be helpful to others that find themselves where I was.
The engine originated from an ebay purchase I made on a whim. It was listed as buy it now for $1500 ... no one bought it, I lowballed when I found out he was not an RC guy, and got it for a song.
On receipt, I found every moving part on the engine locked up. The carb and crank would not move. Hot air gun, oil and patience freed both of them, but it was obvious I was only getting compression on one cylinder.
I've done a lot of engine cleaning work, and have had really good results with the crock pot/antifreeze trick, but there are several rubber boots in this one and I was sweating the bearings might be rusted. For these reasons, I tried mild solvents - WD-40, penetrating oils, pure methanol soaks for days. It helped make it spin freely, but when I pulled the valve covers, I found that only three of the ten valves would move. This thing was really stuck. This led me to decide to pull the front end of the engine off to inspect the cam, bearings, and the source of the stickiness.
Removing the drive washer was fairly easy, levering with wood and heating with hot air - careful here with the Woodruff key. When I pulled the cylinder tops, all but one had the valve rocker assemblies fully locked ... with no pushrods involved, seven of the rockers were locked and the rest were stiff. Of interest, the pistons were pristine on top, and the cylinders looked new. It looks like the Original Guy ran it a couple of times, and then put it in a box as is. The manual gives some specific after run instructions, where long term storage requires flushing with kerosene and adding a lot of after run oil.
I pulled the front of the engine off and was initially terrified of what I saw. The bearings had what looked like rust throughout, and even worse, there are a set of small CAM FOLLOWERS (47064000) which drive the PUSH RODS (47066000). These cam followers are driven by the INTAKE AND EXHAUST CAMS ( 47062000, 47062100), and move in an out of the engine FRONT PLATE (47001600) through holes drilled in this aluminum part. Seven of ten of these cam followers were stuck in the front plate and even with heat would not budge. BTW, when I say "heat", I'm talking hot air gun heat ... I do not ever use a torch in these situations. As I pulled parts out, I kept track of the order of removal, and started cleaning. It turned out that the "rust" was actually softened castor oil sludge from all the solvents I had tried. It all came off with a shortened acid brush, and no evidence of rust on the races. Once cleaned several times and oiled, the bearings felt great. Similar situation with the timing gear bearings and the front bearing in the front housing. All that remained was to get the rockers on the cylinder heads freed and the cam followers out of the front plate.
In the case of the rockers, once the grub screw that secures the rocker shaft is removed, on all five cylinders I had to press them out into a wood block with heat applied. Each shaft had black discoloration, that came off easily with a scotchbrite pad. The rocker pivot holes were cleaned out with strips of cloth, or wood strips. Once cleaned, the shafts fit back into the heads and rocker pivots easily. Similarly, the cam followers needed to be heated and I had to use a small rod ground down to the diameter of the pushrods, to the outside of the follower through the cover hole, and then tap on each one until the follower fell out on the inside of the front housing. Again, black stuff on these pins, which came off with a scotchbrite pad. I chucked all these pins in a drill lightly and spun them against the s-brite pads. Once this was done, and the holes cleaned out with wood strips, the followers moved freely.
The whole internals I could get to were cleaned out repeatedly with alcohol and oils until very little gunk was left. Onto reassembly, which is the fun part of this thread.