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Poorly OS40 repair

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flight108/04/2020 23:38:09
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723 forum posts
36 photos

To remove that bearing Good soak over night in plus gas or one of the newer rust penetrating oils then heat and some good taps should always do it, if not do it again but I use a slightly over size drill bit in the bearing bore turn it in until it bits and use that as leverage to twist pull on the bearing always works.

What I am really interested in know is how are you going to repair that whole in the crank case?

 

Edited By flight1 on 08/04/2020 23:43:58

Jon - Laser Engines08/04/2020 23:46:22
5422 forum posts
263 photos
Posted by cymaz on 08/04/2020 11:43:51:

The con rod has the same part number as the .52. As does the wrist pin

con rod.....45205000

pin....45806000

Tower Hobbies If you can stand the postage

Edited By cymaz on 08/04/2020 11:46:36

i wonder if that means an asp 52 rod would fit. I think i know where a dead one is so i might be able to rob the rod. I am surprised though as the 40 is pretty dinky when compared to the 52

Jon - Laser Engines08/04/2020 23:51:18
5422 forum posts
263 photos
Posted by flight1 on 08/04/2020 23:38:09:

What I am really interested in know is how are you going to repair that whole in the crank case?

Edited By flight1 on 08/04/2020 23:43:58

Dunno. Jb weld, blu tack...not sure yet. Its not like it has to take any sort of load. I could easily cut a small disk of litho plate and just glue it on.

As for the bearing, that puppy wasnt coming out without a fight. Even with a press it took a substantial amount of force as it was completely rusted into the ali.

Even if it was not that bad i would probably have still drilled it through. Its quick, simple, and eases bearing replacement in the future. It might seem extreme to drill a hole in the engine but that part of the case really isnt doing anything. Its not even 1mm thick.

flight109/04/2020 00:15:49
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723 forum posts
36 photos

That con rod fits the fs40s/ 48s and 52s as all got the same part number, I supose the 40 is a long stroke engine and the other two are short stroke

Martin Harris09/04/2020 00:36:20
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9264 forum posts
245 photos

While there may often be a correlation, the stroke is not controlled by the length of the con rod - the crank pin radial distance sets it.

Jon - Laser Engines09/04/2020 08:14:32
5422 forum posts
263 photos

Very true, although it is possible for it to have a longer bore/stroke ratio. Not in this case mind you

In any case, i will begin the hunt for a rod as ripmax are closed anyway so i cant get a new one direct

jrman09/04/2020 09:12:54
375 forum posts
3 photos

Jon, Try Just Engines. They are still open (AFAIK) and have stocks of some OS spares.

Alan Hilton09/04/2020 09:19:12
125 forum posts

Hi Jon

Why not re bush the con rod .I did one on a Pretner years ago when I had access to an engineering workshop

Alan

Doc Marten09/04/2020 10:20:21
543 forum posts
7 photos
Posted by jrman on 09/04/2020 09:12:54:

Jon, Try Just Engines. They are still open (AFAIK) and have stocks of some OS spares.

They are, I've just received my order from them, ASP parts for my TT54 that fit as well as the TT originals.

Engine Doctor09/04/2020 10:41:39
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2469 forum posts
39 photos

Hello John . I have a con rod from a 52 rs that you can have if it will help ? PM me your address and I'll get it in the post . Rod came out of engine with damaged casing .

E.D.

Jonathan W09/04/2020 11:39:25
120 forum posts
11 photos
Posted by Martin Harris on 08/04/2020 23:34:46:

I knocked this up to do the job several years ago - it's never let me down but Jon's one sounded like a challenge!

I left the option to use it as a slide hammer but haven't needed to finish it off...

That's a very neat bearing extractor, Martin. I think all the OS 4 strokes have the same size cam bearing, so I can see why you took the time to make it.

Ref the OS FS40 con rod, it is quite likely to be the same con rod as also used in the OS 2 strokes of the era, i.e. the Max 40 H and 40 FSR. That might open up more possible secondhand sources.

Nigel R09/04/2020 11:49:19
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3756 forum posts
587 photos

I believe it might be 40H. The piston ring is the same (I think!). So maybe OS borrowed the whole rod/pin/piston/ring assembly and removed the lump from top of piston?

Doc Marten09/04/2020 11:59:28
543 forum posts
7 photos
Posted by Jonathan W on 09/04/2020 11:39:25:
Posted by Martin Harris on 08/04/2020 23:34:46:

I knocked this up to do the job several years ago - it's never let me down but Jon's one sounded like a challenge!

I left the option to use it as a slide hammer but haven't needed to finish it off...

That's a very neat bearing extractor, Martin. I think all the OS 4 strokes have the same size cam bearing, so I can see why you took the time to make it.

Ref the OS FS40 con rod, it is quite likely to be the same con rod as also used in the OS 2 strokes of the era, i.e. the Max 40 H and 40 FSR. That might open up more possible secondhand sources.

That's n impressive piece of home engineering Martin and makes me more determined to own a lathe.

How about a thread on home made tools and solutions overcome by ingenuity?

Jon - Laser Engines09/04/2020 12:13:45
5422 forum posts
263 photos

Jrman, yep they are, but given the nature of the project i dont want to spend loads of money just it case it ends up a dud.

Alan, the bushes are ok its the ali that has been munched by the acid it was exposed to.

ED, Thanks very much for the offer but i already bled another chap for an ASP 52fs rod i knew he had spare. If its no good or something else happens i will let you know.

I have made a little more progress on the engine but didnt take photos as it was really quick work. The cam followers, gudgeon pin, pushrods and valves got some abrasive treatment to polish them up. The crank and cams were wire brushed and came up nicely. I shot blasted the valve springs to de rust them but if the engine runs well i will replace them later.

I rebuild the head and the valves appear to seal so all in all its not going too badly. It might actually work!

Martin Arnold 110/04/2020 15:12:00
21 forum posts
3 photos

Just fitted bearings to two of these old OS40FSs in my Super Trouper twin, went stainless steel this time in the hope they won't rust quite so quickly !!!

super trouper.jpg

Jon - Laser Engines16/04/2020 13:31:58
5422 forum posts
263 photos

Since my last post i have received two care packages. One contained the bearings i needed for the rebuild and the other a conrod kindly donated to the cause.

os40 (21).jpg

All that remained was to put it all back together.

os40 (22).jpg

os40 (23).jpg

I am currently still missing the O rings for the pushrod tubes so i left them off. I also need a new cam cover as my plan to repair the old one wont work. I drilled a big hole through it so i can rescue the new bearing without cooking it. The prop driver is also pretty shot and the head shim was shredded so we are going without for now. there is no point replacing these parts unless the engine runs ok so we will see what happens.

I am still quite confident it will run. The exhaust valve is leaking but im hoping it will settle down with a run. It will then be a case of working out if its worth adding those other new parts and making good the hole in the crankcase.

Depending on how things pan out, i might even try running it later this evening

Martin Harris16/04/2020 14:31:28
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9264 forum posts
245 photos

What was your failed plan, Jon? I would have thought you should be able to epoxy an aluminium plug in the hole if you don't want to heat the case high enough for aluminium solder. I'd be tempted to turn up a thin brimmed top hat plug for increased glueing area if originality isn't more important than function.

Jon - Laser Engines16/04/2020 14:55:52
5422 forum posts
263 photos

The o/d of the bearing part of the cover is 15mm so i was going to drill a 15mm hole through a strip of 3mm ali i have. I was then going to put the cover in the hole, drill through the remaining mount lug, and then flip it 180 to pick up the other side. I could then file away to get a new flange which i would then press over the current bearing housing after i turned it to remove the current lug.

It would have been fine, but my ali strip was not wide enough

Martin Harris16/04/2020 15:11:54
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9264 forum posts
245 photos

Ah - I thought it was the drilled holes that needed repair. I'd imagine that you'll be able to pick up a spare housing/cover from any of a multitude of engines if you can't repair yours but the single bolt should retain the housing sufficiently for test running as long as you don't overtighten it. (Granny and eggs come to mind!)

paul d16/04/2020 18:40:45
165 forum posts
11 photos

What a bodge job Jon! working where you do surely you have access to bearing pullers or a lathe to make one? you didn't even acknowledge Martin's suggestion.

So you've "rebuilt" it complete with a hole in the crankcase, a leaking exhaust valve and no shim on the head.....hmm!

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