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Author Topic: fp 35 bearing problems  (Read 585 times)

Offline George Waters

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fp 35 bearing problems
« on: August 18, 2009, 12:15:53 PM »
Does anyone know how or who can fix an fp that pushes a lot of fuel out the front bearing? I bought this engine new and it has about 200 flights on it. It pushes enough out the front bearing that 4.5 oz only gets to the overhead 8. It runs very good otherwise. Thankyou George
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Offline Paul Smith

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Re: fp 35 bearing problems
« Reply #1 on: August 18, 2009, 12:54:16 PM »
These plain bearing, non-ringed engines are basically unmaintainable throwaways.

There are five major wear parts: piston, cylinder, rod, crankshaft, crankcase.   If something goes, something else is probably not far behind.  Don't throw good money after bad.  Maybe you could pick up a replacement from the popular auction site and merge the two enignes to make one good one. 

If the auction engine runs well, you know where to find a pistone y cylindre when the time comes.
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Paul Smith

Alan Hahn

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Re: fp 35 bearing problems
« Reply #2 on: August 18, 2009, 01:35:46 PM »
I have seen one trick which tries to "suck the fuel back-- I think it came from Scott Bair's  article that had measurements of a engine doing 4-2-4.

As I recall, it suggests cutting (or scratching) a circular groove near the front end of the bronze bearing (maybe an 1/8" back from the front). Then you run another groove back, along the upper side of the crankshaft bearing connecting this front groove to the cutout for the venturi. The idea is that the fuel collects in the front groove, and  is then pulled back (via the top groove) into the crankcase during the intake stroke of the motor.

Before doing this, try to get a real copy of the article in case I forgot a detail or 2!

On the other hand, as Paul says, it may just be that your bearing is really worn out and there isn't much you can do except to enjoy the good engine run (Foxes for example run pretty good at that point) and buy a lot of paper towels--a larger tank may be called for too.
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Offline rustler

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Re: fp 35 bearing problems
« Reply #3 on: August 18, 2009, 02:46:47 PM »
If the engine is running o.k. otherwise, what Alan says. I use a amall dia. dental burr in a dremel for the operation. First attempts can look a bit messy, but will work just as well.
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Ian Russell.
[I can remember the schedule o.k., the problem is remembering what was the last manoeuvre I just flew!].

Offline Paul Smith

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Re: fp 35 bearing problems
« Reply #4 on: August 18, 2009, 05:34:41 PM »
The idea of cutting a left-hand thread groove into the crankcase worked well on Cox Conquest 15's that developed front end leaks.  There was a machinist in the club who could and would do a "pro" job at no cost to the user.  As I recall, it was a single spiral groove that made less than one full turn in the length of the front bearing.  Of course this was cut into the aluminum casing between two ball races.

When one of those Conquests developed a loose front end, it would use over an ounce per minute and the fuel spray would get into the pilot's eyes.  The groove dead-stopped it.

I hesitate to recommend that fix for an FP40 because (a) I'm not sure that it would work on that engine, and (b) it involves the phantom machineist that I can't find anymore.
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Paul Smith

Offline Dennis Moritz

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Re: fp 35 bearing problems
« Reply #5 on: August 18, 2009, 05:51:41 PM »
Email me off line. Sending you a present is long overdue.

D
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Offline Brett Buck

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Re: fp 35 bearing problems
« Reply #6 on: August 18, 2009, 08:43:26 PM »
Quote from: George Waters on August 18, 2009, 12:15:53 PM
Does anyone know how or who can fix an fp that pushes a lot of fuel out the front bearing? I bought this engine new and it has about 200 flights on it. It pushes enough out the front bearing that 4.5 oz only gets to the overhead 8. It runs very good otherwise. Thankyou George

    You need an oil return groove.

     Brett
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