Laser 80 Engine

[Kevin Fairgrieve]

I have recently acquired for the pricely sum of £29.50 including postage, a Laser 80 engine.

This engine is in need of a darn good clean up and a good service.

Here in lies my problem. I have no instruction leaflet with the engine and canot find one on the WWW. Does anyone know of a source or has a set that they can scan and send to me please.

Secondly, any advise on stripping down this engine would be most welcome.

Thanks in advance.

[Bob Howard]

Go to www.laserengines.com. The instructions are all on the website.

I am not convinced that your engine is an 80. The plug is inclined forwards, and the silencer & carb are held in by 6BA grub screws. Both of these features were redesigned when the 80 was introduced. Check the mounting dimensions against the data sheet on the Laser website. If the 80 dimensions match your engine, you have a 75.

Stripping down could be a bit tricky, as the cams tend to fall out if you remove the backplate. You will probably never get the timing right again. When I acquired an old Laser with the valve gear gummed up with oil, Neil Tidey (Mr. Laser Engines) advised me to use cellulose thinners - it worked. Remember to give it a good oiling afterwards.

If the valves are coked up, running on synthetic fuel should clear them out a bit.  

I notice there is no carburettor fitted. The original Super Tigre carbs (simple wire needle valve, with a locking nut) were great.  I have a laser 75, about 25 years old, which still runs perfectly. The later S/T carbs, which yours would probably not have had, were fitted with seals which could develop air leaks. This made setting up a bit tricky

If you have no carb, is worth investing in the latest version, designed by Neil Tidey. It works fine, and should cost about £30 - £35. You might need to replace the silencer as well (£12). I had a secondhand Laser 80 which insisted on overheating and stopping - it turned out to be a blocked silencer.

Your engine has a pressure nipple on the side of the silencer - you should not need it. All of my Lasers have always run well withour pressure.

I run my engines on Model Technics Pro-Power 5% fuel, Firepower F6 plug & , for a 75 or 80, an APC 13 x 9 prop. You could also tru a Graupner 12 x 8 3 blade.

 Good luck & happy Lasering!

[Kevin Fairgrieve]

Thanks for the info.

I have the instructions from the Laser website, but just wondered if the printed version was any different.

I believe the valve gear is gummed up as the valves appear not to move when the engine is turned over. I have a tin of cellulose in the shed, and will give that a go.

The carburetter was included with the engine and is brand new. It was just not on for the photo`s. A new silencer will be needed, as this one has been crushed/deformed where it enters the outlet.

I was going on the date from the webesite regarding size. It was sold as a 70, but the dimmensions from the website indicated that it was an 80. So do I have a 75?

I run all my engines on Model Technics Pro-Power 5% fuel, so no issues there. Prop size was a bit of a mystory as I am still not sure what size engine I have..

The angine has been cleaned externally and now looks like a lovely shiny Laser.

Thanks again for the info.

[Bob Howard]

Definitely a 75, so the prop sizes suggested will be fine.

The 70 is much smaller, and has the modified carb/exhaust fixings and plug position.

[Phill Mainwaring]

I have three laser engins a 62, 75, and a 100

wich all run realy nice, when I've had a problem on two ocasions

I've phoned and spoken to Niel Tidey and he couldn't be more helpfull

he's a very nice chap, and if you can't fix it he can

[Bob Howard]

Come to think of it, it could even be a very old 61. The only external difference between the 61 & 75 was the width of the cylinder head, but I have no details to hand what the difference was. You could always email Neil for information.

Re. my Laser 80 with a blocked silencer, I struggled with that problem for months. Neil diagnosed it from a single email. It has been running like a sewing machine ever since.

[Kevin Fairgrieve]

The information on the Laser website gives me an engine bearer width of 40mm. As you probably diagnosed, the engine is an older one and probably is an 75.

If I get no joy running it I will contact Neil. I will have to as I need a new silencer..

Still with Xmas looming it will have to wait till the new year.

Another question springs to mind. On the engine mount lug there are 3 letters. I believe these to be the initials of the original owner. Does anyone know if this is correct?

[Bob Howard]

You have it spot on - all Lasers had the owners initials stamped on them at the factory before despatch. I am not sure if they still do that.

The bearer width of 40mm was common to the 61, 75 & 80, as are the mounting hole spacings.  The 61 was the first laser ever produced, the 75 followed it a few months later.

[Braddock, VC]

They still do it and also the year the engine was bought, I bought a 70 and an 80 and the only trouble I've had with them is they do not run if there's no fuel in the tank.

On 10% prosynth they really do the business, the 80 is at least as powerful as my saito 82 and, if mounted upright, the exhaust points up and the perceived noise is much less than the 82.

My 80 pulls my flair fokker d7 around with a 14 x 6 but is happier (and quieter) wih a 14 x 8. The 70 pulls my KK falcon round with a 14 x 5 prop I bought back in the early 80s for an os 80 fs of which it is at least the equal.

Great engines well worthy of their excellent reputation  and at 29.50 you got a real bargain.

[Howard Tomlin]

my 75 went like a train on a 12x6 prop!

 too many years of castor fuel have lead to coked up exhaust valve, but it still soldiers on.

 my laser 90 has been a pig by comparison, and my laser 150 blew its bottom end out in flight due to oil starvation.

 I honestly prefer saito now , however you cant beat that laser noise!

[vroooOOOM VroooOOOM]

I have a Laser 75 anyone know the crank thread size?

 

cheers

[Martin U]

Does anyone know the HP of a Laser 80?

I'd guess about 1.4

Most engines list their HP by Laser don't.

Thanks

Martin

[David Davis]

I don't know what the HP of a Laser 80 is either, but the commonly held opinion within my club is that Lasers are less powerful, size for size, compared with their Japanese equivalents.

I don't know how well-informed this opinion is.

[Andy Blackburn]

I did a fairly basic test on a Laser 70 some time ago, turned out that it was about 300 rpm better than an O.S. 70 on the same prop and same fuel (APC 12x7, Bekra 10%), neither of which were optimal for the Laser. I guess it will depend on the engine but at the very least they look to be comparable with other engines, I think lasers are generally much better on bigger props, though, and the silencer can usually be cowled.

[Martin Harris - Moderator]

The 150 is designed to be capable of turning a large prop relatively slowly and is quoted as being "equivalent" to a normal 120 but as far as I'm aware this is the only one specifically designed to produce a lower power output than the average 4 stroke glow.

Power figures quoted by manufacturers are usually fairly meaningless as they are obtained under test conditions - the engine's effectiveness is dependant on many external factors, airframe, prop, fuel etc.

I don't know if it's coincidental but Rolls Royce would never quote power figures either - their engines were always described as adequate...

Kevin, if you're stripping it anyway (and do be careful to use imperial Allen keys if it's an early version) you could measure the bore and stroke to calculate the capacity.

Neil always advises not to attempt to remove piston rings - early ones are unobtainable and will almost certainly break if you try to do so. Also, the inlet and exhaust cams are different on some models but what appears more likely to be the inlet cam (to me anyway) is actually the exhaust so don't be fooled into thinking that someone may have swapped them in the past!

Edited By Martin Harris on 13/09/2014 13:10:37

[Stevo]

Martin,

Regards Piston rings... Laser have supplied me with the later model ones, but there are aftermarket ones on ebay for the earlier lasers, I've used them for Lasers, Saitos and OSs... and I thoroughly recommend them ! Search for GavIsCool..

[Martin Harris - Moderator]

That could be handy to know!

[Jon H]

Posted by Martin Harris on 13/09/2014 12:47:05:

The 150 is designed to be capable of turning a large prop relatively slowly and is quoted as being "equivalent" to a normal 120 but as far as I'm aware this is the only one specifically designed to produce a lower power output than the average 4 stroke glow.

With the current range of engines this is no longer accurate. The modern 150 (series 6) is on average 300-400rpm faster than the original on the same prop/plug/fuel. The entire range was totally updated in 2012-13.

Kevin, if your engine is a 75 then 13x6 or 14x6 would be a good choice of prop, the 61 works well on 12x6 or 13x6. for some reason the photos have not appeared on your post so its hard to identify!

[Former Member]

[This posting has been removed]

[Jon H]

oh yea, I totally did not spot that. I was under the impression that this was a new thread!

Oh well. as for the HP question that started off the thread I would say somewhere around 1.2 at normal operating rpm (8000-9000) but no doubt it will be higher at higher rpm