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OS40FS

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Ronos08/05/2020 16:04:14
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206 forum posts
17 photos

Hi all, a quick on for you, Would a carburettor from a OS40FS Surpass fit onto a earlier OS40FS, the one with the spring on the needle.

Jon - Laser Engines08/05/2020 16:49:50
5561 forum posts
271 photos

i think so

I have both types but need to dig out the surpass to confirm. I will get back to you later

Ronos08/05/2020 17:20:05
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206 forum posts
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Posted by Jon - Laser Engines on 08/05/2020 16:49:50:

i think so

I have both types but need to dig out the surpass to confirm. I will get back to you later

Thanks Jon, much appreciated.

Jon - Laser Engines08/05/2020 17:54:41
5561 forum posts
271 photos

Just checked and they look identical to me

Ronos08/05/2020 18:00:11
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206 forum posts
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Posted by Jon - Laser Engines on 08/05/2020 17:54:41:

Just checked and they look identical to me

Thanks Jon, do you think if I just ordered the needle rather than the whole carb, it would fit into the carb body.

Doctor Chinnery01/08/2020 20:42:36
43 forum posts

I have recently revived my old OS40FS - quite old really, last times it flew was in a Radio Queen 30-35 years ago.

The poor old thing was seized solid. Anyway, after anointing with WD40 and then spending the best part of a couple of weeks immersed in stale fuel (a ziplock freezer bag does the job) the old FS cleaned up a treat and after thorough flushing and gentle then increasingly more vigorous turning over without a plug etc etc I started it in my test stand and the years of neglect fell away - easy start as per the handbook with a vigorous reverse flick, as long as you use a biggish (11"-12") prop. Still throttles well with that nice slow tickover I remember.

Now - advice please: Can I, and/or should I use my electric starter to start this lovely old four-stroker, or should I stick to the large prop':reverse flick technique? Also - the crankcase breather tube, the installation I have in mind for the OS neccessitates the use of an 8 inch length of fuel tube to drain the unburnt oil out of the airframe - seem to remember something about the breather tube length to be critical, but can't find anything in the literature. Ideas anyone? Thanks.

Edited By Doctor Chinnery on 01/08/2020 20:45:54

Jon - Laser Engines01/08/2020 21:21:53
5561 forum posts
271 photos

If the engine was gummed up with castor i recommend you strip it down and change the bearings. It might feel smooth, but its likely the balls in the bearings are still stuck and are skidding in their races. Eventually the bearings will breakup and ruin the engine.

As its only an hour job to rebuild it i strongly recommend you swap out the bearings.

Also i know its considered common practice, but never use WD40, 3in1, petrol or cellulose thinners to clean up an engine. Its not good for them.

As for the rest, electric is fine as long ass you are sure its not flooded, the backflick works too. I also would not be too worried about the breather. If OS say 8 inch is fine go for that, although truthfully thats pretty long!

john stones 101/08/2020 21:26:44
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11597 forum posts
1517 photos

What's wrong with WD40 please ?

Jon - Laser Engines01/08/2020 21:31:49
5561 forum posts
271 photos
Posted by john stones 1 on 01/08/2020 21:26:44:

What's wrong with WD40 please ?

Its not actually a lubricant, its a water dispersant (hence WD in the name) and its not going to do your engine any favours if its floating around the crankcase.

3in1 is acidic, petrol wont dissolve castor and will eat most of the seals in a glow engine, cellulose is for paint...not sure why folk use it for engines!

Old fuel is fine but it wont save castor clogged bearings.

john stones 101/08/2020 22:35:07
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11597 forum posts
1517 photos

Cheers, I only use to loosen things, It doesn't eat O rings or seals then ?

Rest I don't use.

Doc Marten01/08/2020 23:53:08
636 forum posts
7 photos

WD40 is actually an excellent cleaner, used for cleaning bike chains and a multitude of degreasing and detailing tasks, you'll be hard pushed to find anything better at the job, its all I ever use it for in fact, never as a lubricant which its useless for, just a cleaner and water disperser.

Doctor Chinnery02/08/2020 01:34:56
43 forum posts

ThankYou for the advice Jon - I guess it's going to be another of those "you're never too old to learn" jobs (I'm glad I'm only 78!).

paul d02/08/2020 08:23:12
190 forum posts
22 photos

Along time ago I seem to remember Brian Winch talking about wd40, apparently it will attack phosphor bronze bushes.

Doc Marten02/08/2020 09:57:36
636 forum posts
7 photos

WD40 Myths

I doubt there is a household aerosol product that has attracted so much fable and folklore.

Paul d,

I'd be interested in reading that, a quick Google search suggests that apart from it's ability to act as a dirt magnet just like any other Kerosene/Parafin based product, it has no ill affect on brass, copper, bronze or their alloys.

Maybe the subject of a new thread?

EDIT- I'll step up to the plate for this.

 

Edited By Doc Marten on 02/08/2020 10:23:36

Jon - Laser Engines02/08/2020 10:24:12
5561 forum posts
271 photos
Posted by Doctor Chinnery on 02/08/2020 01:34:56:

ThankYou for the advice Jon - I guess it's going to be another of those "you're never too old to learn" jobs (I'm glad I'm only 78!).

No problem.

For the cost of a few quid in bearings and a little of your time its well worth it. Sure you might get away with it as is, but equally you might not. Then you end up with a mess like in the photo below.

100bearingfail6.jpg

Doctor Chinnery03/08/2020 09:39:07
43 forum posts

Well, if I needed any further incentive to replace the bearings, you've provided it Jon!

As far as I can see all I require will be the front and back bearings - Model Fixings should have them in stock - I might treat myself to a decent set of metric Allen Keys from the same source while I'm at it.

Now, where do I find a step-by-step guide to to the job, ideally specific to this individual motor rather than the generic videos on YouTube? ( I suppose I could try a ouijah board or in extremis a medium to have a word with The Wizard of Oz ! ) 'Cos I don't want to turn this old favourite into an inconveniently shaped paperweight. ☹️

Denis Watkins03/08/2020 10:36:09
4544 forum posts
123 photos

Take good photos

As you go

I do, so As I find my way back

Peter Christy03/08/2020 12:48:36
1831 forum posts

Jon: I keep a Kilner jar full of red diesel for un-gumming old engines, a tip I got from an old friend (an engineer by trade) years ago. He also recommended contaminated diesel - often cheaply available from garages from people who have topped up their diesel car with petrol!

Any comments on its suitability?

--

Pete

Jon - Laser Engines03/08/2020 12:48:50
5561 forum posts
271 photos

Its a pretty simple job. backplate and head off, cam cover plate off, liner out, mark position then piston/conrod out (can be a fiddle), cam shaft out (photo position first), crank out with a few hammer taps, and then its time to toast it up with a heat gun or similar to get the bearings on the move. One they are out its the same job but backwards!

Jon - Laser Engines03/08/2020 12:53:53
5561 forum posts
271 photos
Posted by Peter Christy on 03/08/2020 12:48:36:

Jon: I keep a Kilner jar full of red diesel for un-gumming old engines, a tip I got from an old friend (an engineer by trade) years ago. He also recommended contaminated diesel - often cheaply available from garages from people who have topped up their diesel car with petrol!

Any comments on its suitability?

--

Pete

As glow engines are designed for methanol anything petroleum based risks damage to seals etc. Equally, castor is not soluble in petrol/diesel so wont actually dissolve.

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