Hi All:

      I put my Fox .25 powered Combat ship into a slight crash and now the p&c has a tight fit the entire length of the stroke.  It was a slight crash into nice soft grass covered turf.  The prop was broken, the foam wing was cracked, and the mounting bolts were slightly bent. This was a sweet running Fox engine, first flip starts, very easy to adjust and gave a great steady run all through the flight!

     What to do now? Should I continue to "break it in" by running it on a test stand? I am afraid to lap the p&c as it is too easy to go too far with lapping a Fox engine.   No, parts for these engines  fron Fox! Perhaps "Hello E Bay." Lol

     Perhaps the most sensible thing to do is to replace the .25 with a .35 Stunt and be done with the problems!!

      What made the p&C get tight after a crash? I cleaned the engine well after the crash.  There was no dirt in tthe engine that I could see as the engine was protected by a large aluminum spinner nut.  Coulld it be that the case got bent slightly?

      Any suggestions?

                                                                                              Tia,

                                                                                              Frank

     Hi Randy:

     I did take the engine apart and saw no damage!

     When the piston is pushed into the sleeve from the bottom. it is quite tight despite how the piston is turned.  The "pinch" is the same no matter how the p&c is oriented.

      The rod, wrist pin, and crank have no obvious damage and all appear to work smoothly.  The p&c has no marks that may indicate damage.  I attempted to clean up  the carbon build up fron the sleeve with steel wool but this did not appear to help.

      Perhaps, I am just noticing a tight p&c fit due to this engine being run on a castor based fuel! As I said, this engine has been a real sweetheart of an engine!

     Any other suggestions?

                                                                                                       Tia,

                                                                                                       Frank
     

    There are any number of things that could be wrong with it -  bent case, for example - that wouldn't be obvious by just looking. It didn't just decide to gum itself up on that one flight that coincidentally ended in a crash.

    Brett

    Brett

Brett Is right about the engine didn't get tight the same time as the crash, if it was not that tight before, and is now, you have a bend, warp, or some type of interference, does the piston go into the sleeve OK when away from all other parts? does the binding start when you put the sleeve in the case ? (bent case) or when you tighten the head or backplate down? does the crank rotate freely with no drag? try to recheck ALL  the parts. Then see at what point it binds.

Randy

      Hi Randy:

      The bare piston is tight in the bare cylinder.  Playing with the case, head and backplate does not change anything with the p&c fit.  It appears to be concentric in the bore so I am just going to leave it a bit tight and run it before I make any more judgements.  It has a great p&c seal and compression now!!!!

      I had the same tight p&c fit with a 65 year old Fox .35 Stunt that I got from E BAy.  I soaked it in penetrating oil overnight and now I have a great running Fox Stunt! Same great compression and p&c seal as the .25! Leave it alone!!!!!!!!!!!!!!!!! Lol

                                                                                     Stay well,
                                                                                  
                                                                                     Frank

I may be mistaken, but from what I remember of the old Fox .25, it was a combination of .29 and .19 parts to come up with the .25 for the free flight gang. A .19 crankcase, .29 piston and sleeve, .19 crankshaft.  Bill Little and I discussed this a few years back.  So those might be a source of parts or you can by one of my .25 stunt engines. Not is top shape, but for a small price plus postage, who knows.

Hi Ty,

You still owe me dinner for overpaying on the NIB .25!   But, since you have sent me a couple sets of plans, and some printed out articles, all is good.

The sleeve for the .25 has notches cut in the lip for the head bolts.  The 29 P/S and .19 case, crank make the .25.  But it seems to be a better stunt engine than either.  A good shape one makes about as much power as the Fox .35 and has an outstanding break.

I have had a Blue Bird in primer for years now and just haven't painted it.  It is powered by a good condition .25.  Will be using a GMA petal blade 9 1/2-6 and 58' .015 lines.  Might be able to go out to at least 60'X.015.  The model was built before Eric ever kitted it so that goes to the time I have had it setting around.

BIG Bear
RNMM/AMM

Randy,

How were you starting that engine? It sounds like the crankpin is bent. - You'll need a new one I'm afraid, try eBay for old fox stuff. - It's  a great source for hard to find stuff, but hey you probably know that anyway!

One other thing you could try:-

Strip the motor down then assemble just the piston/conrod/crankshaft. (Don't worry about the crankcase of bother the liner.) Try to rotate the crankshaft as is with your hands (with the piston and conrod connected). - Observe the crank, if anythings amiss here you should see it instantly. (I got this idea from an early 29X advert:-)

Failing this it would be a good idea to get a donor engine as mentioned previously. This is a pretty reliable way to obtain secondhand parts which are in good nick.

Good luck!


Tim