Lou Crane
Posts: 258
Joined: 5/11/2006
From: Sierra Vista, AZ, USA
Status: offline
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I'm breaking in a pair of these for a friend. First impression is that they are VERY nicely made and fitted - ah, well, they are ENYAs...
Initial bench running with the first of the two showed an unexpected thing. The compression adjusting screw did not back out when the screw was turned back. It could be forced to drop back, by goosing it higher, then dropping it back quickly. Not a good idea when what you need is LESS compression, right now!
It continued doing this over about the first 30 minutes or so of short, heat-cycle runs, so I decided to try something. We'd examined the engine before any running - I always do out of curiosity, and to check for any machining trash inside, and for a look at the parts theselves. (The 25SS has a massive crankdisk, which makes a good flywheel to damp vibrations.) The contra-piston is within a drop-in iron piece, trapped by the outer head, much like a glow engine with a button combustion chamber clamped-on.
So, being careful to NOT disturb the cylinder and piston alignment, I pulled the head and contra-piston assembly to see just how stiff the c/p fit the outer part.
VERY stiffly! So with a small piece of 1/4" dowel, a smooth faced side of the anvil on my bench vise, and a tack hammer, I proceeded to tap the contra-piston back to its highest distance from the shaft. Then, flipped it over, and tapped it down to the other extreme possible position. Repeated this about five times all told. It still felt just as tight as when I first pulled it out of the engine. I hoped, at least, I might have freed the pieces from any locked-up condition.
So it proved! The c/p is still extremely firm in fit, but can be moved both ways. On backing off compression, it follows the screw, slowly, but it follows. It may feel just the slightest bit smoother on raising compression, too, without any suggestion of ever going slack.
Treated the #2 engine to the same 'exercising' of c/p in outer. Hope the effect is as successful.
Anyone else had a similar problem? Were there other solutions than my 1/4" birch dowel 'drift punch' efforts? ...Not specifically with ENYA diesels, but with any... I would not try this with a c/p direct in a working cylinder, but the separate, drop-in assembly sugggested the approach for the 25 SS-D.
It is a fine running engine! Well, was with the 'sticking' c/p, too, but now I have better confidence about not harming it during break-in.
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Lou Crane, Sierra Vista, AZ
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ENYA 25SS Diesel - 
