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Engines and parts required

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Paul james 820/10/2017 23:17:29
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A lot of the guys in our flying club have gone over to all electric but as a bit of an old codger I still like tinkering with engines, particularly 4 strokes. I've picked up a few interesting engines from them and put them to good use in my growing collection of Flair Scout models.

I'm currently rebuilding a Laser 75 but need both the needles for the carb, I can make up the throttle linkage but without dimensions can't do much with the needles. It has the older Super Tigre carb fitted. I could alternatively adapt a carb from a 40 sized Irvine as they fitted those to the later engines.

Also fixing up an older OS91FS which needs a new head as the exhaust manifold has been ripped off in a crash. The rest of the engine is fine and I've got new bearings to go in it if I can find a head. The bare head casting would do as I've all the bits for the head rebuild i the old one.

My grandson is getting a Magnatilla kit for Christmas so I'm ideally looking for a 48 or 52 size 4 stroke for that.

Question is do any of you guys have bits and pieces or complete engines you no longer use cluttering up your workshops that you would like to rehome? I'd obviously pay for anything you might have.

Hope this post isn't infringing any rules of the forum.

cymaz20/10/2017 23:37:17
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934 photos

Check out Jon Harper on this thread. He works at laser and will give you an answer straight from the factory. Helpful chap if ever there was one.

Richard Wills 220/10/2017 23:55:10
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102 forum posts
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Paul,

I have a head from an original OS 91 surpass in my spares. I also have an OS 52 surpass currently going unused, good condition and runs beautifully I could be pursuaded to part with.

Jon Harper - Laser Engines21/10/2017 01:12:11
3087 forum posts
129 photos
Posted by cymaz on 20/10/2017 23:37:17:

Check out Jon Harper on this thread. He works at laser and will give you an answer straight from the factory. Helpful chap if ever there was one.

Its cool, I'm here.

Bad news about the 75 though as I cant supply parts for it any more. Dave at Motors and rotors might have spares for the carb though. All I can supply for the engine is the bearings and valve springs as they are common with our current range.

As the 75 was discontinued 25 years ago we have had to draw the line under them as they are mostly shot at this point

Jonathan W21/10/2017 03:25:46
43 forum posts
11 photos

Try ebay for the ST carb needles

Old style main needle

Idle needle

Paul james 821/10/2017 12:00:41
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64 forum posts
8 photos

Jon has given me some great advice on the old Laser, really helpful guy!!!

The 75 is in such good overall condition that it would be a pity to chuck it.

New bearings fitted so just the carb to sort, I'd like to keep it original by finding the needles from an old ST carb but can still keep that by me and adapt another to use.

Thanks for all the replies guys, too windy for flying today so back to making a few more aluminium prop nuts for the Flair Scouts now

 

Edited By Paul james 8 on 21/10/2017 12:07:54

Paul james 821/10/2017 12:01:53
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64 forum posts
8 photos
Posted by Jonathan W on 21/10/2017 03:25:46:

Try ebay for the ST carb needles

Old style main needle

Idle needle

Thanks for that Jonathan, not sure that they are the correct ones as it looks like the idler has a knurled head whereas the one I have should fit down the inside I think.

Jon Harper - Laser Engines21/10/2017 12:28:36
3087 forum posts
129 photos

If you have a photo of your current carb Paul that may help with finding bits for it.

Hows the compression on the 75?

Paul james 821/10/2017 13:15:03
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64 forum posts
8 photos

Jon,

The carb is with another member of the flying club just now but I will try to get it back and take some photos.

Compression seemed a bit low when I put it back together but I had it firing a couple of times by just squirting a bit of fuel into the intake and it increased quite a bit.

I'm looking to put it into something that isn't needing massive power and think it will be fine. Might be an idea to make a new piston ring at some point but will try it first.

Denis Watkins21/10/2017 14:33:36
2043 forum posts
104 photos

Surely guys, a ringed motor does not feel the same as ABC when turning by hand?

My two ringed motors feel like I have left the plug out when I turn them by finger.

I always thought the ring did not seal until the piston was thrashing up and down?

Richard Wills 221/10/2017 14:59:08
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102 forum posts
7 photos

Sounds like your motors could do with new rings. They don't nip at tdc, but you should still feel pronounced compression on them.

Engine Doctor21/10/2017 15:17:02
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1792 forum posts
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Posted by Denis Watkins on 21/10/2017 14:33:36:

Surely guys, a ringed motor does not feel the same as ABC when turning by hand?

My two ringed motors feel like I have left the plug out when I turn them by finger.

I always thought the ring did not seal until the piston was thrashing up and down?

Ringed motors won't have anywhere near the compression of an ABC engine but you should feel some compression though. The only exception is an engine fitted with a Dykes ring. These are a low friction type ring that only seals firmly against the cylinder sale etc when the engine fires. Not commonly used now but were used in MK1 and Mk11 Irvine's in the 1980's 90's. 

Re the Laser ,have you re -seated the valves? Cleaning them and fitting new springs may have affected the seating resulting in poor compression. Also have you checked that the piston ring is not stuck in its groove with carbon ? 

After stripping many old four stroke engines with poor compression the usual culprit is a stuck piston ring and gently removing it and cleaning the groove restores compression with no parts needed. 

Stevo21/10/2017 16:14:26
2699 forum posts
419 photos

A chap who likes tinkering with four strokes?

I thought I was the only one.. smiley

Jon Harper - Laser Engines21/10/2017 16:50:59
3087 forum posts
129 photos

when you run it up, assuming the valves are seated nicely, give it some welly on a small prop. A 13x6 would be good for the 75. In any event if you give it some it can help bed the rings and valves in after any sort of work

Paul james 821/10/2017 20:23:37
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64 forum posts
8 photos
Posted by Engine Doctor on 21/10/2017 15:17:02:
Posted by Denis Watkins on 21/10/2017 14:33:36:

Surely guys, a ringed motor does not feel the same as ABC when turning by hand?

My two ringed motors feel like I have left the plug out when I turn them by finger.

I always thought the ring did not seal until the piston was thrashing up and down?

Ringed motors won't have anywhere near the compression of an ABC engine but you should feel some compression though. The only exception is an engine fitted with a Dykes ring. These are a low friction type ring that only seals firmly against the cylinder sale etc when the engine fires. Not commonly used now but were used in MK1 and Mk11 Irvine's in the 1980's 90's.Â

Re the Laser ,have you re -seated the valves? Cleaning them and fitting new springs may have affected the seating resulting in poor compression. Also have you checked that the piston ring is not stuck in its groove with carbon ?Â

After stripping many old four stroke engines with poor compression the usual culprit is a stuck piston ring and gently removing it and cleaning the groove restores compression with no parts needed.Â

It has been stripped back completely, ring groove cleaned out properly so the ring floats nicely. I wouldn't say it has any worse compression than most of my OS engines that have been stripped and not run. I will try and get a bit of video of it running once I get the carb sorted.

Paul james 821/10/2017 20:25:22
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64 forum posts
8 photos
Posted by Jon Harper - Laser Engines on 21/10/2017 16:50:59:

when you run it up, assuming the valves are seated nicely, give it some welly on a small prop. A 13x6 would be good for the 75. In any event if you give it some it can help bed the rings and valves in after any sort of work

Will do Jon, what size would you normally recommend to run on it?

Won't be looking for massive power, it will go into something semi scale probably.

Jon Harper - Laser Engines21/10/2017 23:20:10
3087 forum posts
129 photos

13x6-8, 14x6-7, 15x5-6. that sort of thing. Essentially though if the engine sounds happy and is between 8000 and 9000rpm on the ground then you are doing just fine.

Paul james 822/10/2017 11:12:04
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64 forum posts
8 photos
Posted by Jon Harper - Laser Engines on 21/10/2017 23:20:10:

13x6-8, 14x6-7, 15x5-6. that sort of thing. Essentially though if the engine sounds happy and is between 8000 and 9000rpm on the ground then you are doing just fine.

Many thanks!

Paul james 822/10/2017 11:14:20
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64 forum posts
8 photos
Posted by Richard Wills 2 on 20/10/2017 23:55:10:

Paul,

I have a head from an original OS 91 surpass in my spares. I also have an OS 52 surpass currently going unused, good condition and runs beautifully I could be pursuaded to part with.

Did you get my PM Richard?

Would be interested to hear how much you are looking for to help persuade you

Richard Wills 222/10/2017 12:55:22
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102 forum posts
7 photos

You can have the head as long as you cover postage, it is one I got in a job lot, looks good but i'll never need it. The 52 has been in storage for a while, i want to get it down and give it a run to make sure it's still good, then i'll get back to you. Planning to do that as soon as weather calms down a bit, maybe tomorrow.

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