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Laser Engines - Technical questions

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Jon - Laser Engines17/09/2019 10:41:30
4789 forum posts
179 photos

The correct settings on the needle are the settings at which the engine runs correctly. What those settings are for your engine in your model is anyone's guess

To be clear, starting at 2 on the main and 7 on the slow will more or less guarantee the engine will start but it will still need to be tuned up from there.

So much depends on the specific installation you have in the model and then obviously things like prop, plug and fuel all play their part as well.

When i took my 300v out of my La7 and fitted it to my P39 i had to make huge changes to the settings even though both models had the engine inverted and i was using the same prop, plugs and fuel. Just the fuel system setup was different and it made a huge difference to the needle settings as the mains went from only 3/4 open to just about 1.5 turns open. I cant remember what the slow runners did, but they moved a bunch as well.

The fact that your engine was working in the model and now isnt suggests a fuel system problem or a blockage. I have this exact issue with the right cylinder of the 300v in my P39. It keeps going out after about 6 minutes in the air and as the engine has been reliable for years and cleaning the carb has not fixed it then there must be something wrong with the tank or plumbing. Clearly you are in the same boat.

playing with the idle needle is not a problem, in fact many issues can be fixed with a slow run needle adjustment as they can creep over time. If the original settings have been lost it should be a very quick job to fix it as the engine will usually tell you everything you need to know.

If you have compression, glow, and fuel the engine will fire. It might not run, but it has to fire. If it wont fire at all one of those 3 is missing.

If the engine runs for a short time and stops, especially if you prime it before the start, again the engine has told you the problem and is waiting for you to fix it. Simply put, it ran on the prime and then exhausted its supply of fuel. Clearly it needs more fuel at idle, and that is controlled by our good friend the slow run needle. Just open it a bit and try again. If that isnt enough, keep going until it works!

I keep meaning to try and shoot a video showing how to diagnose this sort of thing but its both difficult to shoot and i am too cowardly to stand in front of a camera blush

tigerman17/09/2019 16:05:47
168 forum posts

Now reset the idle jet to 7 turns out then done some fine adjustment to get the tick over and pick up just right then reset the main jet and the Laser is working fine again .Lesson 1 DO NOT MESS WITH JON SETTING .Leave well alone and the Lasser will be fine !!!!!!!!!!!!!!!!!!

Edited By tigerman on 17/09/2019 16:12:06

Jon - Laser Engines17/09/2019 16:08:32
4789 forum posts
179 photos

I always recommend messing with the setting as there is no way i can set it right from the factory to suit every model.

Good to hear its working though.

tigerman17/09/2019 16:22:28
168 forum posts

Next Question .Now I have the Laser 80 working fine I put it in a Seagull Junker C1 According to the manufacture this model needs a 90 4 stroke .Mmm should of listen to my brain and not the manufacture ,just maiden the Junkers C1 with a Laser 80 and wow to much engine .The most you need in this model is a 70 4 stroke ( or even a 60 4stroke ).To get the Junkers to fly scale like with Laser 80 I am flying it on just over tick over , I am using a 14x6 prop .Would I be better buying a 15x6 prop or would this make it worse .I do not have a 15x6 prop to try it ,just thought it would be better t get an expert advice before I brought a 15x6 prop

Martin Harris17/09/2019 16:30:53
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8793 forum posts
215 photos
Posted by tigerman on 17/09/2019 16:05:47:

Now reset the idle jet to 7 turns out then done some fine adjustment to get the tick over and pick up just right then reset the main jet and the Laser is working fine again .Lesson 1 DO NOT MESS WITH JON SETTING .Leave well alone and the Lasser will be fine !!!!!!!!!!!!!!!!!!

Sounds like you've got a result.

As a general rule of thumb on an unknown engine, I always start deliberately rich on both top and bottom ends (a rich engine runs badly and cool, lean may not start and may run too hot if it does) and tune the top end first (remember that the feed to the idle jet is influenced by the main needle setting) then tune the idle and recheck the top end as the idle setting has a small(er) influence over the top end. Recheck until neither need further adjustment.

Andrew Ray17/09/2019 16:32:40
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709 forum posts
19 photos
Posted by Jon - Laser Engines on 17/09/2019 16:08:32:

I always recommend messing with the setting as there is no way i can set it right from the factory to suit every model.

You are too modest Jon wink

Martin McIntosh17/09/2019 19:08:57
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2921 forum posts
1073 photos

I have a few Lasers and YS`s, all of which run on the factory settings with just a few minor adjustments. Managed to buy a number of YS motors at half price because the guys did not know the start up procedure and started to fiddle with them. No way that one of these will start if the idle needle is screwed out more than 1 1/2 turns or the pressure not built up before applying the glow.

I did not need to touch anything on my latest Laser 180 but it will require minor adjustments after a few runs no doubt.

Occasionally you may need to tweak the top end to suit conditions on the day but I see a lot of dead motors at the field due to the carb. fiddlers; after all, you do not tune up your car or lawn mower every day, do you? If a motor was running fine the last time out then a problem must be due to a plug/fuel blockage or a leak.

Jon - Laser Engines18/09/2019 08:27:01
4789 forum posts
179 photos
Posted by Andrew Ray on 17/09/2019 16:32:40:
Posted by Jon - Laser Engines on 17/09/2019 16:08:32:

I always recommend messing with the setting as there is no way i can set it right from the factory to suit every model.

You are too modest Jon wink

Not really, i can only set the engine to suit my test bench so they always need adjusting to suit the model they are fitted too. It might only be 1/16 of a turn on the slow run, it might be a full turn, but they will all need a little tweak

 

Tigerman, just looking at the specs for the Junkers i would agree with you. At 9lbs and just shy of 70 inch i would recommend the 70 as its the smallest engine we do. If you want to tame the beast a little then a 15x6 will help as it will reduce rpm and make the model feel better. I use a 15x6 wood (cant remember the brand) on my 80 powered Hurricane and the performance is good. I keep meaning to get a master 15x6 as it will suit this model even if they are rubbish props.

Kit manufacturers dont always get their engine recommendations right and they usually lean towards overpowering to guard against heavy builders and (i suspect) the american market. The topflite 60 size warbird series are a classic example as the top end 120fs they recommend is just crazy in a 60 inch model. Seagull did the same with their gipsy moth (120 recommended when an 80 is plenty) and black horse did it with their 45cc chipmunk which is just fine on engines as small as 20cc. 

 

Edited By Jon - Laser Engines on 18/09/2019 08:30:35

tigerman18/09/2019 16:51:59
168 forum posts

Thank Jon I will try a 15x6 prop and see what happens

Chris Berry18/09/2019 20:15:24
130 forum posts
1 photos

Thanks to Jon for his advice today.

My 300v in my Flair Stearman was dropping to one cylinder once the glow stick was removed at low throttle. A quick call to Jon and engine was sorted and I flew it two more times.

A lean out on the slow needle and all was well.

Jon - Laser Engines18/09/2019 21:55:10
4789 forum posts
179 photos
Posted by Chris Berry on 18/09/2019 20:15:24:

Thanks to Jon for his advice today.

My 300v in my Flair Stearman was dropping to one cylinder once the glow stick was removed at low throttle. A quick call to Jon and engine was sorted and I flew it two more times.

A lean out on the slow needle and all was well.

Nice one Chris.

Now you can see that fish you will always hear it

And no, i dont expect else anyone to understand that

Chris Berry18/09/2019 22:53:40
130 forum posts
1 photos
Posted by Jon - Laser Engines on 18/09/2019 21:55:10:
Posted by Chris Berry on 18/09/2019 20:15:24:

Thanks to Jon for his advice today.

My 300v in my Flair Stearman was dropping to one cylinder once the glow stick was removed at low throttle. A quick call to Jon and engine was sorted and I flew it two more times.

A lean out on the slow needle and all was well.

 

 

Nice one Chris.

Now you can see that fish you will always hear it

And no, i dont expect else anyone to understand that

I heard the fish so well, I caught it and had it for my dinner!!laugh

Edited By Chris Berry on 18/09/2019 22:54:02

Engine Doctor19/09/2019 10:46:43
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2295 forum posts
27 photos
Posted by Jon - Laser Engines on 18/09/2019 21:55:10:

Nice one Chris.

Now you can see that fish you will always hear it

And no, i dont expect else anyone to understand that

Obviously from the Eric Cantona school of thought smiley.

Chris Berry19/09/2019 22:19:02
130 forum posts
1 photos

Having had many days of good flying in recent weeks I’m running out of fuel for my Lasers. I use Southern Modelcraft fuels and have 3 gallons left until Weston Park.

What other makes of fuel can I use on my single and multi lasers?

thanks

Jon - Laser Engines19/09/2019 22:29:04
4789 forum posts
179 photos

i recommend laser 5 or techpower 5 from model technics. Both are good for all engines of any brand.

if you dont have a shop locally places like leeds models will post it

Chris Berry19/09/2019 22:36:11
130 forum posts
1 photos

Thanks Jon

David Davis01/10/2019 10:18:28
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3399 forum posts
598 photos

Given that Jonathan is probably away on a well-deserved holiday I thought I'd ask the assembled expertise of this forum to see whether they could identify two Laser engines which I own.

One is obviously earlier than the other. It has the Super Tigre carburetter, the rocker box is retained by a single screw and it has a forward facing glow plug. It is stamped 62 RMT on the left-hand engine lug.

The second one has the more modern rocker coverretained by two screws, the Irvine style carburetter and a vertical plug. It is marked JPGR 02. They both run well though cosmetically they are a bit scruffy.

They are both approximately the same size as my Laser 70. I can't seem to be able to get onto the Laser website today.

Don Fry01/10/2019 10:57:27
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3911 forum posts
42 photos

Don't know about the first motor David.

The second, I think the laser carb replaced the Irvine carb in 2005. The 2 screw rocker cover came in in about 2001/2. So it's between those dates. If it is the same size as your 70, it is a 70. The dimensions have not changed. If it's bigger, is one of the bigger engines.

Martin Harris01/10/2019 15:08:43
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8793 forum posts
215 photos
Posted by David Davis on 01/10/2019 10:18:28:

Given that Jonathan is probably away on a well-deserved holiday I thought I'd ask the assembled expertise of this forum to see whether they could identify two Laser engines which I own.

One is obviously earlier than the other. It has the Super Tigre carburetter, the rocker box is retained by a single screw and it has a forward facing glow plug. It is stamped 62 RMT on the left-hand engine lug.

Sounds very much like my own Laser 62 which dates back to the 80s/early 90s. Jon can't supply parts for these but the advice from Neil Tidey was to enjoy running it until something eventually breaks! The engines were/are stamped with the purchaser's initials so it was originally Mr R.M.Txxxxx's...

Edited By Martin Harris on 01/10/2019 15:10:27

J D 801/10/2019 18:37:30
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1253 forum posts
74 photos

In the IC engines page there is a "sticky" section about Laser engine identification.

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