gmeyers

My K & B 7.5 Marines (I now have 5) with the bolt on front ends but rear exhaust, rear carb certainly are not lacking power and all are spinning at 20,000 to 21,000 static rpm. I have never tried anything like a strobe to look for whip because it doesn't appear to be a problem. I can see the spinners next to the fuse and there doesn't seem to be any issues. I do use rigid aluminum motor mounts which I drilled and tapped for 6-32 mounting bolts. I will add that I cannot see any crankcase or cylinder distortion either but I know there must be some.

aspeed

I have a few of the .21 outboards with the crankcase rotated 90 degrees, and a rear rotor .29 right from Bill W. Never noticed anything whip around but the prop.

Sport_Pilot

Pretty sure any movement you see at idle is the motor mount, airframe, and wheels flexing, not the motor housing.

aspeed

On the weedwacker airplanes, yes, but the little guys flop around at certain rpms. Even the reedies on a good test stand

swarf monkey

Gavin Carter here, just seen this message and thought I would reply and attach my present up to date piston ring list, I have all the dimensions to all the rings listed and hold most in stock, if its not on the list then I would need to be sent a good piston and liner to measure up. I can be contacted on here or Ebay or by email: [email protected]
http://stores.ebay.co.uk/GC-Piston-Rings

hsukaria

Thanks Gavin, that's a good list.

GREG DOE

Can anyone suggest a source for a Fox needle valve? What I'm looking fore is the old .29/.35 stunt needle valve that had a cylindrical needle with a tapered flat spot, instead of a pointed needle. I made my own from a 3/48 X 3/4" screw, but it wasn't quite long enough. As long as I'm having to try and find a longer screw, I figured I might as well search for a needle valve. If anyone has a used one in their junk box, that would be fine too. Any help is appreciated. Thanks Greg

Sport_Pilot

Check some of the stunt web sites and forums. Better custom made needles are available.

GREG DOE

Thanks for the suggestion.

miraspen

found out the osmax 20 crank gasket fits the .19 fox! need carb gasket but i can make it myself. having a hard time finding the connecting rod. any help would be appreciated.

VampeD4

My Feedback: (80)

K&B now owns Fox. not sure if you guys new.

gmeyers

MECOA bought a bunch of manufacturers equipment including parts - pretty soon we will need to get anything glow, diesel or gas from them. Their problem is they have much of the machinery parts etc from all those companies but don't have the time or manpower to sort it all out and figure what's what. I can make a con rod for a .19 but FOX made several .19's from back in the baffle days up to the lapped models and the stroke is probably different for each. In the last model they made the BB Schnuerle ports the parts are all listed as one for the sleeve, piston and rod - rod is not listed separately.

ochsnm00

Wow, I didn't think you knew what you were talking about so I went over to MECOA and there they are, beautiful Fox parts, with more to come. They also acquired Webra recently.

carlgrover

Well here's a first for me.

Among others, I have one of the last generation Fox 45s. The one with the big fat high speed needle. Great motor. Lately, it's been a little balky about starting, esp when cold. I have to run the electric starter for a bit before it fires. Yesterday, it never would pop. I put my finger on the carb and pulled it through. No problem, wet finger. I pull the plug and it's glowing orange. So why no start? I tried starting it at several different throttle settings. No luck. Then I opened up the needles. No sale. So then I decided to switch to the glow driver on my power panel and set it in the middle of the voltage range. So soap. In desperation, I turned up the voltage on the power panel all the way and I get it going. Started and stopped several times so I had to keep hitting it with the electric starter until it kept running. I get up in the air and it's running like a champ. Held a great needle. Go for a second flight and it's even worse about starting. Now it's balky and won't stay running so I'm leaving the starter and ignitor on it while it's only half running. Finally, it runs on it's own and away we go for another perfect run. I use 5% fuel (same as always) and it was about 55 deg. out. Nice smoke trail. Pulled like a mule on crack.

Now I figure I have a weak plug on my hands but I didn't have a spare on me to try out. However; whenever I've had a bad plug in the past, the motor would quit running the second the ignitor was removed. Never had an engine be so hard to start yet run so good once it got going. Maybe the plug's getting weak.

Anyway, I've never seen an engine act like this after flying for 30 years.

carl

Cougar429

My Feedback: (3)

Check all your fasteners for tightness, especially the head. Along with a wonky plug you may have a leak develop when the engine warms up.

I used to buy an entire card of Fox plugs at their booth at the Toledo Show every spring. For some reason would eat through the plugs quickly till only one left. That would work fine for the rest of the season.

When flying in colder weather usually have to switch to a hotter plug such as #3 or even "F", but that is not necessary until getting down into the 30's or lower.

Heating it with external power is not a completely true indication of condition as the filament wire can become encased in microscopic wear particles which can interfere with direct contact and catalytic action that keeps it hot when removed. Normally you would be able to fire it off, yet no needle tweaking will keep it running reliably when heat removed.

Is the engine mounted straight up? Condition and age of fuel?

gmeyers

I suspect the fuel but it could be most anything - check the type and content of oil in the fuel - it should be 18% to 20% real (spelled REAL) castor. FAI fuel to 10% Nitro is usually ok and it should be reasonably fresh. Last the glow plug on orange means it will probably go real dim with fuel under compression. On cool days a good battery is needed to lite the glow plug to bright yellow orange - by good I mean a full 1.5 volts (rechargeables are only 1.2 volts) A Fox miracle plug is a last resort.

carlgrover

Oil is right in that percentage. I add 3 oz of castor to every gallon and the fuel already has 18% oil. Other engines using this fuel run fine. This engine runs great once it gets going. It's just harder than heck to get the fire lit. The glo plug is no way glowing orange/yellow. It's just orange. My flight box battery is fairly new and is huge (tractor battery). However; the power panel is old. Maybe it's the problem. The plug is a Fox RC long (not a miracle plug).

carl

GREG DOE

It sounds like something is leaking air. Check the tank and fuel lines for leaks. Make sure the back plate is not leaking. check the O ring seal on the carb.

gmeyers

My current FOX stable consists o f a Special Betty Fox assembled Eagle 74 ABC , 5 or 6 Fox 40 BB Delux ABC's and 5 Fox 46 ABC's, a Fox .19 BB Schneurle lapped and a Fox 25 BB Schneurle lapped. 2 of the venerable Fox 35 Stunt, and a couple of Fox 1/2a parts engines.
I first met FOX back in the 50's when the .15 that would not run was introduced. The Local Hobby Shop asked me to to make them run without voiding any warantees but it couldn't be done. Fox had a cylinder head problem and they simply wouldn't run. So the Hobby Shop sent them all back. But I was declared the official engine guru for the hobby shop which meant that I had to break the new engines in for folks and hop up some for combat flyers - and handle all the engine repairs, overhauls and problem solving.

carlgrover

I got to run my Fox 45 Sunday and put a new Merlin plug in it. No more starting problems.

Now for another question: I found a pretty big Fox muffler. I think it's for a .60. Did Fox make one big muffler to fit the 60, 74, and 78 engines they made or is there a different muffler for each size? This one is a tilt down.

Thanks,

carl

earlwb

Fox made a tilt up and a tilt down muffler for the .60 and .74 engines. The mufflers were the same size. In the past Fox also used to make a Fox Quiet Muffler which was a long length item that worked like a tuned muffler. The Fox Quiet Muffler also came in a tilt up and tilt down type too.

The Fox .78 used the same mufflers that the Fox Hawk .60 and Fox Eagle I engines used. These mufflers do not fit the Fox Eagle II, III or IV .60 engines or the Fox Eagle .74 engines and vice versa.

Now then the MVVS 10cc engine mufflers happen to be an almost perfect fit. You may or may not need to widen the screw holes in the MVVS mufflers ever so slightly to fit with a jeweler's screwdriver.

Hobbsy

My Feedback: (102)

Then it looks like this. This is a .50 or a .46.

carlgrover

Thanks for the information. I've seen quite a few big Fox engines at swap meets but they never seem to have the muffler. Now I'll have to go back to prowling around the swap meets to find one.

carl

gmeyers

I have had a couple of FOX 60' and 74's and the mufflers were all different . They were powerhouses though . I learned that the Rossi 60 header can be made to fit one of the Eagle 60''s to use it with a tuned pipe though I always used the muffler. I'll get back with you if I can be of some help but knowing the spread of the muffler mounting holes might be useful.

earlwb

MECOA took over the MACs mufflers and tuned pipe website and they kept the chart of header sizes and screw dimensions too.]
ref Untitled Document
You can see from the measurements that a MVVS muffler screw spacing is about 1mm more wide that the Fox engines. Which is about 1/2 of a mm per side. Using a small jewerls screwdriver let you widen the holes slightly to fit is needed. Sometimes the muffler holes are wide enough to work with no problems.

Fox .60 Eagle III (bolt-on)
Irvine .61
(screws 6/32 x 1/2" socket head)
(center to center = 34.80mm/1.370")

O.S. .50 FSR & .61 FSR (bolt-on)
ASP .61
Enya 60X
MVVS .61-.77
Webra Speed .61-.70 F (bolt-on)
(screws 4mm x 12mm socket head)
(center to center = 33.91mm/1.335")
(Moki.61 M7 looks like it will fit,
being tested waiting for results)