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Os 1.20 Surpass I bearings

Old 06-13-2013, 04:27 AM
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ESSAR
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Default Os 1.20 Surpass I bearings

Hi guys, I have a great old OS1.20 surpass pumper that needs a new set of bearings/ I was wondering if anyone knows what bearings I need and maybe Had any pointers for the replacement. I Have replaced bearings in Saito engines but never in an OS and I wasn't sure what the procedure was to set the timing correctly. Any info would be appreciated.
Thanks,

Andrew.

Photos of the engine are here(it won't let me upload pics for some reason):

www.rcuniverse.com/forum/m_11024093/anchors_11024459/mpage_1/key_/anchor/tm.htm#11024459


Old 06-13-2013, 09:33 AM
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Campgems
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Default RE: Os 1.20 Surpass I bearings

The O.S four strokes all time the same. With the engine at TDC the dot on the cam will be pointing on a line along the push rods. Either up or down, but on that line. If it is off by one tooth, it is quite noticeable. The hardest part of the tear down is getting the wrist pin out of the piston. You take the head off, then you have to pull the liner up just enough that you clear the hole in the back of the crank case. You will pull the wrist pin out of this hole. Turn the engine over to the point you see the white plastic cap on the pin. Us a dry wall screw and screw it into the plastic and pull it out. You just screw it in enough to allow you to pull it. Now, you pull the wrist pin the same way. The pin is usually varnished up a bit so you need to help it. I have used the drywall screw successfully, but others use and easy out or an old tap. The pin is hard so all you are doing is wedging a tool into it to help you pull it out. Don't loose the little plastic cap, it has to be there or the wrist pin will score the liner Once the pin is out, pull the liner and piston. Then you can remove the rod from the crankYou will NOT be able to get the rod off the crank until it is free of the piston. Any attempt to remove it without doing the above procedure will damage the crank, rod, and or crank case. Once the rod is off you push the crank out the back, same as with a Saito. Of course, you pull the prop drive hub first. The O.S. has a larger opening in the crank, so driving out the main bearing is easier. Just watch that your punch is not catching on the cam follower edge or you can do some serious damage to the crank case.The bearings are standard one. The main bearing is open, the nose bearing is shielded one side although some use shielded both sides IE ZZ suffix on the bearing numberA 6000zz (10x26x8)is what you want for the nose, and a 6002 (15x32x9) for the main. The cam bearings are 695zz (5x13x4)I have been very pleased with the bearing I have used from a company on EBay, USA-Bearings and belts http://stores.ebay.com/USA-Bearings-...p2047675.l2563 Their Quality on their Premium bearing is very good and the price and service are great. Just make sure you get the Premium ones. The standards are not as good.Don
Old 06-13-2013, 10:03 AM
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Default RE: Os 1.20 Surpass I bearings

Thanks for a very informative answer Don.
I have ordered the bearings and will attempt to disassemble the engine completely following your instructions over the next couple of days.
Thanks again for the info,

Andrew.

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