Andy J Posted May 29, 2021 Author Share Posted May 29, 2021 Given the engine is far from reliable and keeps stopping decided to press on with a full strip down today. All parts came apart fairly easily with the exception of the piston pin which refuses to extract through the crank case hole so yet to remove the bearings. Left the crank case and con rod assembly soaking in thinners overnight in the hope that assists freeing it up. One think I did note that was not a single gasket on any of the assemblies so that may account for the poor running. Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted May 29, 2021 Share Posted May 29, 2021 On 21/05/2021 at 18:38, Manish Chandrayan said: MR 6001 C3 for the rear bearing . If you get the sealed or shielded ones remove the shields or seals. Front bearing being MR 608 2RU C3 . Remove the rear rubber seal . MR 695 x 2 for the cam bearings The Os 52 Surpass came as new with a double sealed rear bearing and I believe the front was too. Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted May 29, 2021 Share Posted May 29, 2021 Pretty sure the only gasket on this motor is the head gasket/shim, everything else is a machined fit. Quote Link to comment Share on other sites More sharing options...
jrman Posted May 29, 2021 Share Posted May 29, 2021 Cutaway drawing confirms that the only gasket is for the head. https://www.os-engines.co.jp/english/line_up/engine/air/single/pdf/34200.pdf It also appears to show the rear bearing is shielded (at least on the rear side) but the front is open (at least on the rear). Quote Link to comment Share on other sites More sharing options...
Manish Chandrayan Posted May 29, 2021 Share Posted May 29, 2021 11 minutes ago, Martin Arnold 1 said: Pretty sure the only gasket on this motor is the head gasket/shim, everything else is a machined fit. How about rear cover and the cam cover? Quote Link to comment Share on other sites More sharing options...
Manish Chandrayan Posted May 29, 2021 Share Posted May 29, 2021 Given that the breather is located between the two bearings, if the rear bearing was completely sealed how would the excess blow by oil from the case travel out? Quote Link to comment Share on other sites More sharing options...
Manish Chandrayan Posted May 29, 2021 Share Posted May 29, 2021 (edited) Decided to open up my. NiB 52 and answer some of the questions. No gaskets on the rear cover or the inlet manifold. The rear bearing is sealed from rear. Not dismantling any further. The front bearing is shielded from one side The first two pictures are of the spare front bearing from OEM. The third picture shows (barely) the sealed surface of the bearing (on to the right of the connecting rod) Edited May 29, 2021 by Manish Chandrayan Quote Link to comment Share on other sites More sharing options...
jrman Posted May 29, 2021 Share Posted May 29, 2021 Exactly as indicated on the cutaway and stated in the advert. Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted May 29, 2021 Share Posted May 29, 2021 34 minutes ago, jrman said: Cutaway drawing confirms that the only gasket is for the head. https://www.os-engines.co.jp/english/line_up/engine/air/single/pdf/34200.pdf It also appears to show the rear bearing is shielded (at least on the rear side) but the front is open (at least on the rear). Taken from the part number on your exploded view. https://www.rcjapan.net/index.php?main_page=product_info&cPath=80_413_429&products_id=12730 Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted May 29, 2021 Share Posted May 29, 2021 50 minutes ago, Manish Chandrayan said: Given that the breather is located between the two bearings, if the rear bearing was completely sealed how would the excess blow by oil from the case travel out? Yes see what you mean on that, think it works on the theory that the seal isn't perfect and oil will get through and replace the grease in the bearing anyway, similar to a Saito double sealed front bearing. Just as an aside, most Saito singles come from the factory with a shielded rear bearing and a double sealed front, the oil can easily pass through the shielded rear, as above for the front. Quote Link to comment Share on other sites More sharing options...
Manish Chandrayan Posted May 29, 2021 Share Posted May 29, 2021 Yes shields are not meant to be seals and they will allow oil mist to pass through. Not sure about rubber seals though Quote Link to comment Share on other sites More sharing options...
Andy J Posted May 30, 2021 Author Share Posted May 30, 2021 Well finally managed to get the piston out using a blow torch to release the build up of gunge as overnight soaking did not work. Found that the original rear bearing has a seal on the rear face (cylinder side) with the front bearing having a seal on the front. Tried to get the cam gear bearings out using the same method of heating but neither will budge so they will have to remain. Checked the schematic and confirmed what others said that the only gasket is the cylinder head which quite surprised me. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 30, 2021 Share Posted May 30, 2021 17 hours ago, Manish Chandrayan said: The first two pictures are of the spare front bearing from OEM. The third picture shows (barely) the sealed surface of the bearing (on to the right of the connecting rod) Nasty looking blemish on the con rod. I'd be asking OS to comment on it before I gave it any work! I know you're in India but the UK importer honoured a manufacturing fault in a second hand but unflown engine that I was helping a clubmate with several years after it was originally sold - their comment was that it didn't matter about its history and there was no time limit on a manufacturing fault. Note the (or rather lack of) teeth on the gear! Quote Link to comment Share on other sites More sharing options...
Andy J Posted May 30, 2021 Author Share Posted May 30, 2021 Well finally got one of the cam bearings out using the wax method (thanks Manish) but the other cant be shifted using wax. Then found I have unfortunately purchased the wrong size bearings for the cam so yet another error! Who said working on engines would be easy. At least I found the cylinder head gasket which was attached to the head assembly so its one less item to buy. New shaft bearings installed front and rear so at least the crank-shaft feels very smooth now. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted May 31, 2021 Share Posted May 31, 2021 (edited) On 29/05/2021 at 19:25, Manish Chandrayan said: Yes shields are not meant to be seals and they will allow oil mist to pass through. Not sure about rubber seals though Sealed bearings are just that. They won't allow any lube liquid or mist to pass the seal. They are very useful replacement on any ballraced engine that sprays fuel out of the shielde front bearing . I've had a few red Irvines that have benefitted from sealed front bearings being fitted as it increases performance and fuel economy. The inner seal is of course removed before fitting. I wonder if Martins comments about manufacturing faults are still valid as I have a OS 10LA that has the chrome peeling off the cylinder ? Might be worth a phone call to Ripmax ? Edited May 31, 2021 by Engine Doctor Quote Link to comment Share on other sites More sharing options...
Andy J Posted May 31, 2021 Author Share Posted May 31, 2021 Would anyone know the optimum size for the O rings on the valve push rod covers? Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted May 31, 2021 Share Posted May 31, 2021 Measure them with a vernier. You need inside diameter and cross section to order O rings. Nitrile ring will be fine for an engine as Viton rings will be more expensive. Quote Link to comment Share on other sites More sharing options...
Andy J Posted June 5, 2021 Author Share Posted June 5, 2021 Engine is back together but runs unreliably as prior to all the bearing changes I have done. Engine has a tendency to occasionally throw the prop and will not tick over. Would have double checked the valve clearance but alas the borrowers have taken my vernier gauges so yet another purchase is required. Quote Link to comment Share on other sites More sharing options...
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