I would like to know how to date these Fox engines

batjac wrote:"I would like to know how to date these Fox engines"


I find that lying about how much I make helps...

The Smooth Mark

Ha ha Mark , I was thinking the same thing

Thank you Ken.
That was very interesting.
What makes the muffler valuable?

Fox has made several attempt at providing a proper working muffler. The blimp style muffler you depict in the upper left isn't correct for that engine. Let me restate that, it's the proper style but that version which is screwed together with the straight slotted screws wasn't made available until the late 90's. Fox did away with roll pins in the 80's. The blimp style buts up to the exhaust stack which is a crappy way of a connection. The small ears on the side of the crankcase are subjected to a lot of stress and they break off rendering them useless. The fix to this is to obtain 3/16" steel brake line tubing and cut two pieces which are measured from the back of the ear to the front of the stack. JB weld them up to the ear and to the side of the case. This prevents over tightening of the ears and supports the muffler slightly better.

        The blimp style muffler usually falls apart. The roll pins would shake out and the tail end falls off. Keep in mind if one is flying control line and even a wheel falls off, your disqualified. Not only is it a penalty for the competition flyer, someone could get real hurt or other planes damaged in the pit if something like a muffler flies off. The exit of this muffler is far too small and needs to either have it's stinger cut off. I cut them off to enable a 1/2" opening. This keeps the back pressure from being too excessive. It also keeps the muffler out of the landing gear when mounted on a profile. So either you cut it off, or let the landing gear break it off for you. It's a easy choice to make. In a crash, the muffler WILL break the exhaust stack and it will destroy your fuel tank at the same time. This makes it double fun. Secondly, it breaks the ears off of the case which now can't be used any longer.

      Now that I've explained some of the negatives of the blimp style, I will explain the positives of the middle Sportster series. The muffler itself is quite rare as it was made for less than 5 years. The front cap is machined aluminum, not cast. Your front cap is missing which seriously impacts the value of this muffler. Yours has a piece of wood epoxied into the front. The end cap was also held in with roll pins so they could've fallen out. Two styles of these front caps were made. One was short and the other long. In the situation of your engine, the front cap if not the correct version will extend into the prop swing  area. Someone may have removed it so that it wouldn't strike the prop therefore plugging the muffler with a piece of wood for now. I generally install a aluminum spinner backplate minus the spinner which can pack the prop out enough to provide enough clearance for it to swing.

For me having a machined cap is a plus because I know it's not going to break. The muffler itself encapsulates the entire exhaust stack. This is not just a slip fit, it takes a bit of pressure to slip it on. This is a huge plus not only to prevent the engine from damage in the event of a crash, it assists in providing it from coming loose. If one is going to use a strap, THIS IS THE MUFFLER TO DO IT WITH ON A FOX. This muffler with a strap will interchange with older pre ear .35 stunts. The stack holds the muffler and strap will just retain it. The Fox .15 also had a muffler of similar stack design which would enable the use of a strap on the .15X. The problem is, it's hard to source and when it comes available, they go fast.


The exit of the stinger is slightly larger than the blimp style but it too requires opening up and I drill them out to the maximum I can achieve. This muffler utilizes  2 styles of attachment, the side ear style of attaching which is how yours is attached and the over and under screws which are in the crankcase itself. NEVER use the over and under screws unless it's your only option. These are through holes which have the cylinder liner directly behind them. If the screw touches the cylinder it will distort it and essentially ruin the engine. However, if one is careful, they can get by with using them but installing the screws is very tricky, at least for the one on the bottom.

     This is quite a essay as to why the muffler is valuable but for others who aren't certain, it can be beneficial. I'm sorry for being long winded.

akjgardner wrote:

batjac wrote:"I would like to know how to date these Fox engines"


I find that lying about how much I make helps...

The Smooth Mark

Ha ha Mark , I was thinking the same thing

I was thinking of:

Gassing them up (those Foxes) with some booze, wait till they have enough to where they are lit (really drunk) and then let them go!
Just stay out of the way when you let them go because you'll never know what will happen?
Maybe you'll be able to a phone number from one and be able to date one of them?
We are talking about Glow engines? Sorry