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Thread OP
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Discussion
OS FS 40 questions on rebuild
Hi all,
I am tearing down a eBay buy he said it ran well and ideled smoothly. Maybe it did but boy am I glad I am rebuilding it. It is full of old dried castor. Any way I seem to have a wrist pin going through the rocker assembly. The few I have seen tore down on YouTube did not have his what is the story? Should I heat then tap it out or is there a better way. What years did they make these pre surpass engines? I ordered new bearings but have no idea where to get the 4 orings for the push rod tubes. A new piston ring would be nice also. Is the crank bearing a press fit? Thanks |
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Last edited by Cadmandu; Feb 15, 2018 at 08:39 PM.
Reason: Adding picture
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If you heat it and try to press it out , you will break off the centre ,square casting , it goes through . The casting has a very small grub screw that locates on a flat machined into the rocker shaft. Once removed the shaft should push out by hand . That is just a nicely oiled , castor fuel engine , heaps of them around in all shapes and sizes . I make "O" rings from fuel tube of the right size , preferably neoprene . Most bearings are press fit , how much is a point of preference ! And you haven't even tried to remove the gudgeon pin yet !!! ENJOY .
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Thread OP
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I did remove the small set screw in the rocker casting but was affraid to push on the wrist pin until I heard from you guys. I wonder why some have his design and other 40's just have a shcs ?
Some bearing ate press fit on the shaft and some in the housing. What is your opinion on opening up the air bleed hole? Thanks for your help |
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I have two of these engines. If the bearings are not rusted just soak the engine. The parts for this engine are almost unobtainium. If anything is broken, you will be in a pickle. ATF4 is a good fluid to clean and soak bearings. I used it on my two with complete success. Remember, heat is your friend.
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You may struggle with the wrist pin removal. it can be done but don't be in a hurry. Use penetrating oil and heat. Don't know why you would want to enlarge the air bleed hole.....
I use a small arbor press to remove and install replacement bearings. The hardest one to remove will be the cam bearing in the cylinder block. Maybe leave that one in place if it turns smoothly. I did and extensive rebuild on the marine version of that identical engine last year so speak from experience regarding the wrist pin. |
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Over the years , I have probably cleaned and reset hundreds of these engines . I think everybody used them for the Texaco event in old timers at some stage here in Aust . To be honest I think you should have at least given it a run before you started to strip it as it probably would have been OK as it was . They have never been a power house by anyone's stretch of imagination , and never will be . They are just a great little reliable engine that never seems to wear out , although I have seen some absolute disasters in my time that people have done to them , but they just keep running . I hate it when people use initials to describe something , what is a " shcs " ??? Or is it something like making the breather nipple bigger for some ungodly reason ?
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Quote:
Given all that I am amazed that so many people want to pull engines apart to replace what may be perfect bearings. Seems to be an American thing. So I hope that the bearing replacers order C3 clearance bearings to the OEM specs. * Danny M * |
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.40 ramblings
Well, i have two of these engines. One looks to be complete, just needs a clean and likely new bearings.
The other, i believe, is missing some carb parts and a muffler nipple. I consider it a 'parts engine' It seems OS modelers do not mess with that buried cam bearing unless it looks bad. You can use wax and a wooden dowel to push it out if needed. We Americans seem fascinated with 'bigger is better.' But really i am liking these small and medium glow engines. Sure i admire the larger engines, but these .40 to 1.00 size 4-strokes seem practical (If you want a .40 that makes some real power....check out the Saito FA-40A. It has a 2-needle carb like its larger brothers and can idle low right there with them. A real gem but the price recently went up to $199 ) But don't toss out these older engines! My friend educated me about the old OS FS-40 explaining it had great fuel economy and was reliable. I think it looks sweet too |
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Thread OP
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You guys are probably talking me out of the bearing replacement. I will just clean, soak, and time and adjust the valve lash to .003 is that a good clearance. Please look at this picture and tell me if I should be seeing this on top of my piston. I see an image of the valves. Will the atf clean my valves ?
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Last edited by Cadmandu; Feb 17, 2018 at 06:27 AM.
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That is strange, but i do not know if that is good or bad.
I wonder if the valves getting dirty, might they leave a mark. Hmm. |
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I would say , not being able to check ,only look at pics , that it is more along the lines of the carbon buildup on the head of the valves that has caused the marks on the piston . If it was here I would soak it in Chem Carb , a cleaner in a bath hot , that is used in the aircraft industry out here, and left in for about 4 hrs , the carbon would fall off quite easily and give the valves back their clearance . The engine has clearly only been run on castor oil mixed fuel , proberbly with excess castor , and I would change to 50/50 castor /synthetic and 15 % total in the fuel . Maybe the ATF will soften the carbon , if you don't try you won't know , valve clearance I don't measure , I just give them enough ! Make sure the valves seat and there is no loose carbon on the inside of the inlet and exhaust chambers before you refit the head . I don't think you would regret not changing the bearings , you could heat the crankcase in your oven to about 100/150 degrees and then drop it in ATF , completely covered in the oil and let it cool . The oil will get around it just fine, drain it over nite and put together , should be a nice engine .
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