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Poorly OS40 repair

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Jon - Laser Engines17/02/2020 08:58:07
5752 forum posts
275 photos

I have been presented with an early OS40 4 stroke in a rather sorry state but i am pondering giving it some tlc and trying to get it going again.

The thing i was really wondering about was if i should shoot a video of the process. It would a new thing for me entirely, and somewhat terrifying as i am not one for public performance, but i was an idea that came to mind.

The alternative would be to just post the photos here as normal, assuming there is sufficient interest for that!


Denis Watkins17/02/2020 09:07:28
4693 forum posts
135 photos

Definitely a movie Jon, showing the dark art.

How many times do we ask about 4 strokes

Bearings, timing, valve springs, gaps

Invaluable for me so there must be others

Nigel Dell17/02/2020 09:11:00
493 forum posts
50 photos

I will second a movie Jon, always interesting seeing this.

Frank Skilbeck17/02/2020 09:28:25
4932 forum posts
114 photos

Video would be great. I've got an OS40FS, one of the originals, had it from new, bought in the early 80s, hasn't run for a few years but it's all oiled up and in better condition than your one. 12 x 5 was my favourite prop on it.

Alan Hilton17/02/2020 09:28:29
142 forum posts

Hi Jon

That looks a right mucking fess !, is the conrod bent ?

A video would be great ,timing those OS four strokes isn’t something I havent done befor


Martin Harris - Moderator17/02/2020 09:42:59
9799 forum posts
264 photos

It looks like it's had an impact against something or someone has tried jamming something in there - perhaps in the process of removing the prop nut? Will you do some stress relieving or put a new rod in?

It looks like it's spent some time immersed or in a very damp place.

Repairing the cam cover will be an interesting exercise.

Don Fry17/02/2020 09:47:00
4557 forum posts
54 photos

I'm interested. I know absolutely nothing about the innards of engines. The only time I've even slightly dismantled one is to check valve gaps, and a crowning achievement, putting the timing back to normal on my Laser 75, purchased as a scrap, non runner.

extra slim17/02/2020 09:58:30
523 forum posts
49 photos

do it, good guy on you tub e David Mcintyre in the states does similar, tear downs, reassembly, plus engine runs.. you could get a few tips by watching some of his stuff..

Jon - Laser Engines17/02/2020 10:30:38
5752 forum posts
275 photos

Looks like i dropped myself right in it with the video idea.

So, small video's of a few minutes showing the progress at each step or one longer one covering the whole thing?

Nigel Dell17/02/2020 10:44:13
493 forum posts
50 photos

I think Jon it’s what you are comfortable doing otherwise you are making it more stressful, at the end of the day it is the imparting of information that is the important thing.

Denis Watkins17/02/2020 11:47:39
4693 forum posts
135 photos

As above, with Nigel

Fit this in at your own pace in your own time

Short reports are fine

Nigel R17/02/2020 12:26:52
4418 forum posts
717 photos

first question - how do you clean the outside!?

Jon - Laser Engines17/02/2020 12:44:09
5752 forum posts
275 photos
Posted by Nigel R on 17/02/2020 12:26:52:

first question - how do you clean the outside!?

Watch the video

I think before i get too carried away i need to see what it is i have got here. Each part needs to be inspected and cleaned to see if its even worth trying to rebuild it. That process of inspection an cleaning could be a video in its own right so that is probably where i will start. When i will start, cant say.

Also the idea i have in mind is a sort of looking through my eyes video so there will be no music or slick montages showing the work. JohnnyQ90 on youtube does great projects but his standard of video production is well beyond me. Literally, if i do it then it will just be me yapping on while trying to clean something so it should be a good cure for insomnia if nothing else

ken anderson.17/02/2020 12:57:27
8858 forum posts
820 photos

another thumbs up for a video jon...its a while since I did the bearings on a 91..

ken dept.

Don Fry17/02/2020 13:39:26
4557 forum posts
54 photos

I found the best teachers were not the flash, gobby ones. The best knew their subject, conveyed their knowledge clearly, and did 'in other words', to get the less quick a second go at understanding.

Neil6717/02/2020 15:52:55
208 forum posts
4 photos

Video would be great!!

Foxfan17/02/2020 16:44:42
931 forum posts
7 photos

Yes please, a video.


2W17/02/2020 17:06:16
107 forum posts
18 photos

Go for it Jon!

A series of short video clips describing what, why and how would be great as the project progresses. Not many of us have your level of expertise and experience on small engines, and I for one am keen to learn more. You are guaranteed at least 12 fans to watch your efforts!


kc17/02/2020 18:15:36
6946 forum posts
175 photos

Take photos and consider submitting an article to RCME

Malcolm Fisher17/02/2020 18:34:47
671 forum posts
7 photos

Jon, I have an OS 40 Surpass in bits. Crankcase has a crack and bearings are badly corroded. As far as I know the other bits are in reasonable condition. You are welcome to the lot if it could be of use to you.


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