Relocating the crankcase breather on my OLD FS-40...
12-15-2002, 05:29 PM
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Relocating the crankcase breather on my OLD FS-40...
Dear Fellow OS Four Stroke Engine Fans:
The PIPE Here...and my ANCIENT, "pre-Surpass" OS FS-40 four stroke engine is in need of new BEARINGS, as it's been making that dreaded "grinding" or "mechanical whizzing" noise at idle, and I have a FULL set of crankshaft AND CAMSHAFT bearings coming from Boca Bearings to do the replacement with-and I also recently acquired the "Guide to OS Model Four-Strokes" by Graham Rice from the US RC Modeler magazine book collection to assist me in the teardown and reassembly of that great little vintage "putt-putt mill" of mine.
Since I've noticed just about ALL the OS, and also Saito made single cylinder four strokes nowadays have their crankcase breather nipples fitted into the NOSE section of the engine, I was wondering if it MIGHT be advisable to relocate the backplate located breather on my FS-40 into the nose section of the crankcase (between the front and rear crankshaft bearings) and just plug up the old threaded breather hole with a "cut-off" metric thread screw to allow the relocated breather to operate properly. Where the engine will be partially torn down-especially for the parts that operate inside the crankcase-doing this during the crankshaft/camshaft bearing replacement process would be a VERY easily accomplished modification.
One reason I have for doing this is where I've got those worn out bearings in the engine, perhaps the backplate located breather nipple did NOT allow enough of the oil IN the model fuel I use-which is FHS Red Max 10% nitro, 17% all synthetic oil four stroke fuel-to get through the rear crankshaft bearing into the nose of the engine, where the camshaft drive, the camshaft and ITS bearings, and the pushrod's lower ends are located! Just think for a minute-if the breather DOES get relocated to the nose of the FS-40 engine, like the newer OS and Saito four stroke singles have it set up, the pressure could well be GREATER in the crankcase for the function of getting the oil in the model engine's fuel moved forward with each downstroke of the piston through the rear crankshaft bearing into the camshaft drive area-and thusly avoiding just about ANY possiblity of the crankshaft and camshaft bearings, and all the other moving parts IN the valve gear, from "running dry" due to lack of pressure to move the oil through the rear bearing FROM that backplate located breather nipple!
One modification I DID do on the FS-40 already that HAS worked out great was done to the FS-40's carburetor airbleed hole-my old FS-40's airbleed carb just NEVER allowed the engine to idle properly, and after reading a recommendation on the Internet to drill out the airbleed hole ON the FS-40's carburetor to about 2mm (0.078 in) diameter to allow the engine to idle a bit more reliably, I've had nothing but SUCCESS
in having the FS-40 idle SO slowly after it's all warmed up that one could almost count the prop blades...and also, where the FS-40 WAS OS' first front camshaft four stroke design, perhaps the backplate located breather nipple COULD have been an engineering "faux pas" that made the early FS-40s wear out their ball bearings a bit MORE easily than they would have with a "under-the-nose" loacted breather nipple!
Even my small Saito FA-30 four stroke has the nose located breather nipple...so, would relocating the old FS-40's breather nipple from the backplate to the underside of the nose of the engine's crankcase, between the front and rear bearings, be a good idea? I'd sure like to find out if anyone else has likewise done it before I try to do it!
Hope to get some good answers...I'm listening!
Yours Sincerely,
The PIPE!
The PIPE Here...and my ANCIENT, "pre-Surpass" OS FS-40 four stroke engine is in need of new BEARINGS, as it's been making that dreaded "grinding" or "mechanical whizzing" noise at idle, and I have a FULL set of crankshaft AND CAMSHAFT bearings coming from Boca Bearings to do the replacement with-and I also recently acquired the "Guide to OS Model Four-Strokes" by Graham Rice from the US RC Modeler magazine book collection to assist me in the teardown and reassembly of that great little vintage "putt-putt mill" of mine.
Since I've noticed just about ALL the OS, and also Saito made single cylinder four strokes nowadays have their crankcase breather nipples fitted into the NOSE section of the engine, I was wondering if it MIGHT be advisable to relocate the backplate located breather on my FS-40 into the nose section of the crankcase (between the front and rear crankshaft bearings) and just plug up the old threaded breather hole with a "cut-off" metric thread screw to allow the relocated breather to operate properly. Where the engine will be partially torn down-especially for the parts that operate inside the crankcase-doing this during the crankshaft/camshaft bearing replacement process would be a VERY easily accomplished modification.
One reason I have for doing this is where I've got those worn out bearings in the engine, perhaps the backplate located breather nipple did NOT allow enough of the oil IN the model fuel I use-which is FHS Red Max 10% nitro, 17% all synthetic oil four stroke fuel-to get through the rear crankshaft bearing into the nose of the engine, where the camshaft drive, the camshaft and ITS bearings, and the pushrod's lower ends are located! Just think for a minute-if the breather DOES get relocated to the nose of the FS-40 engine, like the newer OS and Saito four stroke singles have it set up, the pressure could well be GREATER in the crankcase for the function of getting the oil in the model engine's fuel moved forward with each downstroke of the piston through the rear crankshaft bearing into the camshaft drive area-and thusly avoiding just about ANY possiblity of the crankshaft and camshaft bearings, and all the other moving parts IN the valve gear, from "running dry" due to lack of pressure to move the oil through the rear bearing FROM that backplate located breather nipple!
One modification I DID do on the FS-40 already that HAS worked out great was done to the FS-40's carburetor airbleed hole-my old FS-40's airbleed carb just NEVER allowed the engine to idle properly, and after reading a recommendation on the Internet to drill out the airbleed hole ON the FS-40's carburetor to about 2mm (0.078 in) diameter to allow the engine to idle a bit more reliably, I've had nothing but SUCCESS
in having the FS-40 idle SO slowly after it's all warmed up that one could almost count the prop blades...and also, where the FS-40 WAS OS' first front camshaft four stroke design, perhaps the backplate located breather nipple COULD have been an engineering "faux pas" that made the early FS-40s wear out their ball bearings a bit MORE easily than they would have with a "under-the-nose" loacted breather nipple!Even my small Saito FA-30 four stroke has the nose located breather nipple...so, would relocating the old FS-40's breather nipple from the backplate to the underside of the nose of the engine's crankcase, between the front and rear bearings, be a good idea? I'd sure like to find out if anyone else has likewise done it before I try to do it!
Hope to get some good answers...I'm listening!
Yours Sincerely,
The PIPE!
12-16-2002, 10:09 PM
#2
My Feedback: (11)
Relocating the crankcase breather on my OLD FS-40...
Pipe,
Actually, moving the breather hole won't help much at all. That's because the corrosion is caused by fuel residue that's sitting in the engine after the day's flying. Your best bet is to literally flood the engine with after-run oil at the end of the day. Then suspend it nose down to make sure the oil gets a chance to run forward into the cam and front bearings. A baggie on the nose of the model keeps the oil from messing up the floor.
Actually, moving the breather hole won't help much at all. That's because the corrosion is caused by fuel residue that's sitting in the engine after the day's flying. Your best bet is to literally flood the engine with after-run oil at the end of the day. Then suspend it nose down to make sure the oil gets a chance to run forward into the cam and front bearings. A baggie on the nose of the model keeps the oil from messing up the floor.
