FOX 35 CRANKSHAFT BEARING

I WANTED TO USE A FOX 35 FOR MY TF NOBLER, RUNNING THE ENGINES IN MY COLLECTION TO FIND THE BEST ONE. THEY ALL HAD THE SAME PROBLEM, EVEN THE NEW ONES. THE CRANKSHAFT WOULD WOBBLE IN THE BEARING, CAUSING THE PROPELLER TO WOBBLE, LOTS OF OIL LEAKAGE. NORMAL FOR A FOX 35, WITH A SOLID BEARING?

I want to go ahead and get this question out of the way..
Don't take offense, but what content, and type of, oil is in your fuel?
I haven't Experienced the prop "wobbling" on a Fox with a balanced prop, even on some pretty old ones, so just can't think of anything except maybe too low or all synthetic oil having been used. Sorry.....
Bill Little <><

>I WANTED TO USE A FOX 35 FOR MY TF NOBLER, RUNNING THE
>ENGINES IN MY COLLECTION TO FIND THE BEST ONE. THEY ALL HAD
>THE SAME PROBLEM, EVEN THE NEW ONES. THE CRANKSHAFT WOULD
>WOBBLE IN THE BEARING, CAUSING THE PROPELLER TO WOBBLE, LOTS
>OF OIL LEAKAGE. NORMAL FOR A FOX 35, WITH A SOLID BEARING?

If you are talking about crankshaft "rock", some slight play is normal on most of these- if it gets excessive- say prop tip runout is more than 1/16" or so, then the bushing is on the way down and out. They can be replaced, but another fix is to chrome the shaft bearing area then ream the bushing out and lap to fit. It depends on how much metal is left in the bearing. I had an old Torp .29 GH that was so worn you could rock the prop almost 1/4", the bearing was visibly eliptical- still ran well tho.

john

Here's what I do with foxes where the crankshaft wobbles in the bearing. Since the Fox has a 7/16" dia. crankshaft, I take a 7/16-14 tap and run it through the bearing. Doing this displaces some of the bronze bearing material, making the I. D. of the bearing smaller. I then carefully work the crankshaft back into the bearing using oil and turning the crankshaft with pressure until it protrudes through the other end. Keep in mind that the fit is tight now, so you should chuck the threaded end lightly in a hand drill and spin it until the crankshaft turns easily in the bearing. This method has the advantage of not only rescuing the engine from the trash can, but of adding a lot of oil grooves to the I D of the bearing virtually eliminating any further wear. I've done this to several Fox engines and after many hours of running time, the crankshaft is still snug in it's bore.
Will

I just ran an old McCoy 19 last Saturday morning.

I purchased it in 1963 or so...(for $3.95!)...

This was it's first run since 1965...with a period glow plug to boot...some fun!

Used sig 25% castor/10% nitro, a 9/6 Zinger and it would turn 10,300 in a wet 2 cycle. In a 4- cycle...a blubbering 6,500...don't think that it will move much of anything in a 4 stroke!

Ran great, started easy, but was really dribbling fuel out the front of the case.

After the run, a rather more experienced eye, not mine, mentioned it looked to be wobbly to about .002+.

Runs, but messy!!! Half the fuel, and castor oil, runs right out the nose of the case!

The tap trick to expand the bushing, mentioned in the last mail...sort of like reaming?... sounds pretty drastic...chroming the shaft up sounds more conservative, but don't you have to turn or at least polish the crank then for a uniform surface?

Is it possible to re-bush? or does plating the shaft make more sense?

Rebushing sounds like a potential disaster if the case wasn't designed to accomadate the procedure.

This is an interesting topic as a LOT of us have older engines with nostalgic value only, and a "correct" repair would be worth doing just to keep the "old crock" running. Not cost effective, but like taking care of an old dog...no pun intended.

Any of you machine shop savy/engine building types to weigh in on this?

Thanks, Pete

It would be cheaper to replace both the case and crank than chroming the crank and reaming or boring the bushing to fit the crank. If anybody know who can do this, in-house, other than GMA, I'd like to know who. Replacing the bushing isn't a huge deal. Greg Davis of Port Coquitlam, BC, Canada, has been known to do that in past years, but I don't know if he would now. Steve

>It would be cheaper to replace both the case and crank than
>chroming the crank and reaming or boring the bushing to fit
>the crank. If anybody know who can do this, in-house, other
>than GMA, I'd like to know who. Replacing the bushing isn't
>a huge deal. Greg Davis of Port Coquitlam, BC, Canada, has
>been known to do that in past years, but I don't know if he
>would now. Steve

Bob Oge... And he does beautiful work- so does Don Blackburn...
Next question?

Hi Guys; I have some fox 35,s that have really loose crank bearings, but still do not leak. There is a groove in the bushing that takes the oil and fuel back in to the cranckase on fox 35,s, and if it gets plugged up even a tight bearing, will have a very wet front end. Most Foxes only run better on a loose bearing anyway to a point. I have some that are so loose that they rattle as I flip the prop to start the engine, but run like crazy and don't leak. Jim

Jim,

Thats an interesting observation on the Fox front bushing. Particularly about how a seemingly overworn bushing closes up with heat and running and gives a good run.

Something I was hoping to see on this thread was some of the "machine shop" savy guys just relate how the procedure of re-sleeving an engine is done.

Namely, do you just progressively drill out the bearing after referencing everything 90 degrees to the cylinder...and how do you do that?

Press in a sintered brass?/bronze? sleeve without cracking the case...heat the case and shrink the sleeve?

Then ream the bushing till it fits the crank...assumed/checked to be true? And the reaming is perpindicular to the piston/rod/

Or chrome the crank to match the bushing..and avoid the whole thing!

In other words, what are the procedures to perform a seemingly simple but needfully accurate machine shop procedures?

The fact that an old McCoy or Fox is not worth the expense is assumed to be secondary to reviving an "old buddy" to see some more action.

Also, a new rod...how hard to do if you have the measurements and a blank of forged aluminum...drill, turn, bush, HOW?

Stuff that would be interesting to know for the un-initiated.

PS...sold my Dad's lathe 5 years ago...just wanna know HOW!