Fox 35 engine IDs?

[pmackenzie]

Hi,
   Question for the Fox experts.
  I bought these on ebay, but not sure what they are exactly
The one on the right looks sort of like the 35 R/C motor, but a C/L version.
The one on the left, despite the case style, not sure it has a rear bearing. The front looks to just be a bushing. There is a pressure tap into the crank journal.
Perhaps a slow rat or carrier motor?
Both are in great shape, not sure either has ever been run. The liner was in backwards on the right motor

I have to contact the vendor though, the motor on the right should have been a .25BB R/C motor! (See second image from the ebay ad)
Don't actually want the .25 but figure they might want to know they messed up

Thanks,

Pat MacKenzie

[kenneth cook]

                  The left engine is a 35X. I still have the box from my fathers 35X which he purchased it about 1964, it had the blue and chrome sticker which in his particular box was known as the blue ribbon special.  The front is bushed with a caged needle bearing on the rear. The next gen was the 36X which later had a R8 ball bearing but the earlier versions had the needle bearings as well.

                 The engine on the right is known as the Sport .36. It was available in a .29 displacement as well. .29 would be stamped on the lug. The innards of the Sport .36 will exchange with the Fox Combat .36X. The mufflers that were available for this version work on the .35 stunt rather well. The blimp style that Fox last used is quite a turd. The Sport muffler aside from it falling apart unless you riveted it, offers a lot less restriction and it encompasses the entire stack.  They did make a r/c version and the case and crank are slightly longer than the control line version. Bill Mohrbacher had mentioned to me that this engine was developed in the .36 size to use in slow combat which required a bushed case. I have had good success with these and not so good success. Some of my poorer running versions of this engine have extensive binding issues in the lower end and the engines don't turn up too well. On the other hand, I have a few that run quite well. I prefer the larger knob needle valves they used as they work a lot better over a stunt .35 needle but the spraybar diameter is considerably wider.

            I wouldn't of dismissed that .25. The .25 BB that's shown in the picture is a terrific engine and works quite well. In addition, it maybe the lightest BB .25 produced. In addition, it offers a lot of power. Many blow that engine off especially after using some of the earlier Fox .25's. The engine does vibrate a tad but it works extremely well.

[pmackenzie]

Thanks for the response.
I was actually sort of interested in seeing the 25BB. It always seemed to me to be the most "modern" engine Fox ever made.
Just not sure I would have had a use for it.

The Sport .36 could see some use in a Vintage Combat speed model, since the rules (the one time it was flown locally) specified a plain bearing loop scavenged motor.

With apologies to Brett , I have the back cover off the 35X. Someone has "breathed" on it a bit: rod is polished, bypass cleaned up.
Big hole in the crank, I had a MK III like that and it eventually broke.
I will post some pics of the internals once it is all cleaned up.  From what I see so far it was run a bit, but very little.

[Dwayne Donnelly]

Thanks for the response.
I was actually sort of interested in seeing the 25BB. It always seemed to me to be the most "modern" engine Fox ever made.
Just not sure I would have had a use for it.

.

80 mph  combat?

[pmackenzie]

80 mph  combat?

I have several other motors for speed limit. From previous experience BB motors are too strong/fast/heavy.
But I would have probably tried it, had I actually got it

[kenneth cook]

             I use the .25 LA primarily for speed limit, going up against the Fox .25 BB I couldn't touch it. Al Ferraro or New Jersey used them for speed limit. Whenever we would be in a match, I was always surprised how well the .25 BB performed. Fox made a .19 in the same case which is equally as powerful.

[pmackenzie]

Getting off topic , but I have mainly been running TT25 in speed limit . In my experience they are stronger than the LA.
Plus they last a lot longer. I started out with three of them back when speed limit first started to be flown, and until they died in mid-airs they kept working.
I am down to one now, still works well, but getting hard to hot restart. LA25 is my backup.

Fall 2019 I bought some more from ebay and RCG, which I had hoped to run last season. CV19 had other ideas , but hopefully this year they will see some use.
I also bought a couple of Brodak 25 as well.

I would have tried the Fox, but didn't bid on the ebay sale because of it. I wanted the old combat motor, to make an old fast model

[pmackenzie]

Some pictures of the motors torn down.
This is the Sport 36. Very clean, not sure it was ever run.
Eagle eyes might notice that the rod is in backwards!
So whoever did have it not only put the liner in backwards, but the rod as well.
Only managed to lose one circlip putting it right!

[pmackenzie]

Here is the 35X. You can see the rear roller bearing, that runs directly on the crank.
Interesting that there is no bearing material in the crank journal, the crank just runs on the aluminum case.
Also quite clean, did not see much running either.

Did see something interesting though, there is a small void in the wall of the piston on the exhaust side.
Looks like a flaw in the original part, not done through some sort of damage, because there is no distortion of the piston around it.
About the same width as the divider in the exhaust port so it should not leak, but possibly could grow and cause the piston to fail?
I could grind it out to clean edges, but then it would be open when the piston is in parts of the upstroke.
A bit of side port action perhaps ?

I will probably just run it as is till it fails.