Hi there. So tonight I made a trek to the city to rescue this old engine. I did not know what it was when I left home but knew it was a control line engine on an rc plane. It needed a new home so I went to pick it up, only to realize it was a slant plug Fox .15 with muffler. It is locked up solid, but I was able to get the head and backplate off. I will be giving it a good bath In antifreeze next week to clean and free it up. But what I am mainly looking for is an approximate year of manufacture so I can try and find an instruction sheet. I guess after cleaning it all up in will probably have to break it in again. Thank you in advance.

Hello Chancey
The Fox looks like a late model engine going off the matt grey finish and the muffler mounting lugs could be mid 1980's.
A RC one was reviewed here:
http://sceptreflight.com/Model%20Engine%20Tests/Fox%2015%20RC.html

Attached are instructions for my Fox 15X which is earlier but still largely applicable.
Regards Gerald

Hi there. So tonight I made a trek to the city to rescue this old engine. I did not know what it was when I left home but knew it was a control line engine on an rc plane. It needed a new home so I went to pick it up, only to realize it was a slant plug Fox .15 with muffler. It is locked up solid, but I was able to get the head and backplate off. I will be giving it a good bath In antifreeze next week to clean and free it up. But what I am mainly looking for is an approximate year of manufacture so I can try and find an instruction sheet. I guess after cleaning it all up in will probably have to break it in again. Thank you in advance.

        << Obligatory Hurl reference here>>

   

             Not much mystery to the Fox .15's. The first version was the Rocket. It's more commonly called the steelfin due to it's steel exterior liner. I happen to be a fan of all of them. They run pretty good in old timey planes of the period. I had two of them have their heads crack almost directly in the center along the fin. I'm assuming that's why the head was redesigned. The next generation was the slant plug which is what you have. I believe the steelfin has a wrist pin with polished ends. This was detrimental to the life of that cylinder as most that shared the same commonality. If it cuts grooves into the liner, the engine quickly becomes a shelf queen. The slantplug may have brass end pads. My memory is lacking but as most Fox engines, you don't want to just start taking things apart without making a witness mark due to the fact that Fox doesn't index the cylinder. The steelfin though was different as the head screws passed through the liner indexing it.

         I'm a fan of of all the Fox .15's and I own all but two. There was a .15XX and I believe there may have been a XXX. Those had red anodized connecting rods and they were based on the slant fin case with more power as the porting was also changed. The next generation was a lot different. This was the era of the Schneurle porting and Fox made this with a newly designed case called the tall back or coffin case. This engine used Schneurle porting and it was a plain bushing. The next version was the Fox .15 BB which had a ball raced crank. The coffin back series also utilized a head button and a head clamp for the plug. Duke offered low compression, high compression and a racing head button.  The engines are  heavy, but they're quite powerful for what they are. These engines migrated towards combat and Duke made a Fox .15 BB which used the same diameter crank as the large .36 displacement Mark series combat engines. Very few of those were made.  My experience with them has proved that they like to turn up and while the 8" prop is recommended they do much better on 7" props. I have also noted that the  steelfin and slant plug also worked better for me using wood props.

Just a little update. I dropped it in the little pot for about 3 hours. Removed the head, backplate, spraybar, and prop drive washer. Brushed it all off, blew it off followed by a wiping. I put a few drops of 3-in-1 oil on a few places, front of crankshaft, rear of crankshaft, in teh venturi, on top of the piston, on teh connecting rod connection points. I then reassembled it and wiped it off. It has a fair amount of compression to me. Now to just have a free evening, hopefully in the next week to hear it start up once again. Here are a couple of pictures of the results. The 8 x 6 prop is what was on it when I got it, but will have to try and find a diferent one next week for running as the hole is larger than the shaft.

Check the liner and piston with a magnet. It it's a steel & iron pair you want lots of castor.

Thank you again for the great tips, advice and help. Since I have it back together again, I will remove the muffler and check through the exhaust with my magnet.

                No need to check the piston, it's a iron piston and ledloy liner.          Using Omega would not be recommended. This engine will work well with all castor fuels. Keep the oil content over 20%.  I use Powermaster 50/50.  The engine will run with that muffler but it's not going to like it as it promotes overheating.   Don't overtighten the muffler either. Once snug, put some CA on the threads and on the ears of the case and leave it be. It can seriously distort the case which will cause a bind.  I remove all the guts from those mufflers and drill out the exit to create a better flow. These engines don't tolerate heat well. The nipple on the spraybar is quite small so I recommended using a piece of copper wire to cinch down your tubing onto it when you do use it. The orientation of the spraybar is simple. You want the hole at the same angle of the venturi. Some will tell you angled back a bit, not really necessary.

Sorry I forgot to ask earlier, being as I was told it was kind of newer, what kind of fuel would be recommended? Would Omega 5% be ok, or is it best to try and source out something with mostly castor? Thanks again.

Hi Chancey   DO NOT use  Omega  or any other  RC sport fuels, minimum use  22%  half castor, start very rich, then lean slowly  to pont where is cleans up right a a 2 cycle,
You will not get a second chance to break it in,  f its been run before  you have what you have,  I would use a  8 x 4  to  run the engine , and use a hot plug, should be a  Short
I had one of these on a  Shark 15 and  it did a good job of flying it

Have fun

Randy