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OS 52 Surpass bearings

Old 12-30-2023, 06:12 AM
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Default OS 52 Surpass bearings

Can someone recommend a service facility for an older (early 2000s) OS 52 Surpass 4 cycle engine that may need bearings. I've changed bearings on many 2 cycles but never tackled a 4 cycle. Thanks! Bill
Old 01-04-2024, 02:36 AM
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You change bearings on a four stroke the same as on a two stroke. You heat the case with a propane torch (have done this for over forty years) and slam the case against a wooden block...and the bearing just fall out. If not... cool the case in water and repeat the heating process.
Old 01-04-2024, 05:48 AM
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Where are you located? Asking as I have offered to do this work for others for just the cost of parts and shipping, (along with my own, do this for friends, as well). Last was a Saito 50 which proved challenging to find parts due to how long out of production. Shipping each way cost the owner around $25 so would think that a good estimate. My only caveat is in this case any recommendations be followed. The number of parts to properly make the work worthwhile, or even if the engine is economically salvageable at all could not be made until after an inspection and assessment.

As Jaka54 describes, bearing replacement is identical to many other engines, (of course, there are a few oddballs such as RCV and YS) but reassembly takes a bit more care to properly align and adjust the valvetrain or other secondaries such as fuel pumps, regulators, etc.

Also, due to the parts count there could be a bit more cost for parts. Along with the requisite gaskets and seals, there could be valvetrain components. One area I pay close attention to with OS are cam and followers, valve springs, valve stems and keepers. Cannot tell if anything else required till an inspection.

NOTE: This inspection is normal for any engine across my build table as to be honest, I have seen many more damaged 2-strokes than their more complex brethren. Nothing really complex, just more parts to look over.

Only problem with this time of year would be the final step of test and setup on the stand. May have to wait till warmer weather if do it here. If you go this route and decide to run it yourself you need to treat it same as new and follow the break in procedure, (this is true of ANY repair with new parts).

Each make provides something unique. RCV is designed like no other engine, rotating the barrel itself to provide porting. This means a simpler design, but one that tends to run much hotter so proper cooling is even more critical. On the subject of YS, I found that most problems with assembly and setup were improper regulator housing orientation, bad diaphragms, (or placement) and one odd but common problem of a warped valve cover. Without a good seal there many will simply not run right.

ps. I would recommend looking for something local first as they may be able to provide you a face to face teaching opportunity, as well. That's why it's best to provide location with your avatar.
Old 02-27-2024, 04:50 PM
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Thaks for all the responses. I got a set of bearings from Boca and went to work! The original bearings were tough to get out, oven @ 225 deg F for 30 mins. After two banging on wood then reheating cycles they came out. I removed the shields on both sides of the rear bearing and the shield facing the rear, on the front bearing. Today I ran it on my test stand with a MAS 12-6 prop and S&W 15% 2 cycle fuel. (more oil than dedicated 4 cycle fuel) It ran very well, quiet and smoothly. The low end needle needs some fine tuning. That's for another day. I will replace the Type F plug in the spring, the one in service now doesn't look like it's in very good shape.

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