Laser Engines - Technical questions

[Rich Griff]

Gosh, perhaps a servicing nipple for the rockers, a one oiling point for them with dedicated oil ways, but then some spark will fit the gaskets the wrong way which then block the oilway, so lots of thought needed so that cannot happen, with oe parts at any rate.

 

Perhaps a dedicated syringe so required oil quantity injected at   the 3 hour check and service.

 

A sight glass for oil level checking prior to the days running ?

 

Not researched laser engines yet but I think I saw a chap who made them way back in the 80's/90's at llyn penrhos site ?

Edited November 2, 2021 by Rich Griff

[Jon H]

2 hours ago, David Hazell 1 said:

OK, so I always tell myself "No question is a stupid question", but I might be pushing the boundaries here...

 

Noob query. I searched for "LASER LUBRICATE" on here to try to find a definitive answer but there wasn't anything directly applicable to the Shiny new Laser 70 in my paws. Nor is there anything in the instruction sheet to tell me: How much lubricant through the breather nipple before first running in? I think I have some two stroke motor oil for a gasser I've never gotten round to flying so will decant some into a little bottle with a bit of fuel tubing for application purposes...

 

Also, Do I have to perform this (and rocker) lubrication step every three hours running? I see in an old version of the instructions it says to do that, but not on the instructions I received with my engine...

 

Oh and What torque should the prop nut be tightened to? I have a decent cycle torque wrench that would come in handy for me to be able to "get a feel" for how tight it needs to be once I have torqued it a couple of times.

 

I will have many more questions but these are the first ones...

 

Thanks in anticipation!

 

Although i have updated our instruction sheet over the years some of it is pretty old. To clarify your questions...

 

 

How much oil to inject before running - None. I already ran it, its good to go. 

 

How often to lube the engine and rockers - Never. The fuel has oil in it and there is an oilway cut into the cam follower bush to push oil into the rocker cover. If the engine is inverted the rocker cover will usually fill up completely. This causes much hysteria for some reason. The only time it needs extra lube is if its been dismantled and cleaned and in that case you need to blob it on the conrod/crank pin. An oil enema up the breather nipple wont really help it due to the construction of the engine. The best way to keep it oiled up and in good condition is to keep flying it. 

 

Prop torque - Tight enough to not fall off ? There is no figure i can give im afraid. Wood props will tolerate less torque than nylon, carbon somewhere in the middle i suspect. Just tighten it up as you do for all your other engines and it will be fine. 

 

You didnt ask, but glow plug torque tends to cause more problems as folk go mad doing them up. You do not need a 2 foot torque wrench to do up a glow plug. Finger tight and then a slight nip. Its not a high tensile job! 

 

 

 

Beyond that, check valve clearance after the first hour of running and then annually after that (unless performance is declining). The biggest maintenance job is cleaning. If you nose over in the weeds dont just restart it and fly. Cowl off, engine cleaned, cowl cleaned, carb intake free of rubbish etc. All that dust and rubbish will get into the carb in the end so give it a good clean. Even a simple prop strike can throw dust and dirt into the cowl so focus efforts there

Edited November 2, 2021 by Jon - Laser Engines

[Chris Walby]

Oh and don't forget !

1. Don't run it rich
2. Warm up and tune as per Jon's recommendations
3. Give it a good thrashing so no flying around at 1/4 throttle with it super rich
4. Enjoy the sound of your little Laser ?

[David Hazell 1]

I've got a painstaking wait until I can get the plane built - going to be a few months at least - Laser will be bagged till then in most likelihood.

[Paul De Tourtoulon]

And don't forget to anneal the copper gasket / washer on the plug, and don't cross thread it either !

[Jon H]

57 minutes ago, Paul De Tourtoulon said:

And don't forget to anneal the copper gasket / washer on the plug

 

 

Do what now? ?

[Nigel R]

must admit, I've been missing that step out for years, too

[Paul De Tourtoulon]

I got my metre of 18/12 stainless today, 7€ + 13€ post it is proper Stainless non magnetic,,,

[Paul De Tourtoulon]

I an  ran it this afternoon, the Bolly 14.5 x 8 gave me 9.700 rpm but although well screwed down the rubbish seagull plastic cone took a couple of bites out of both blades.?

 So I owe you a prop David,,,

[Jon H]

I was sent this by a customer who was having trouble. I often request that customers send a video of their problem as its much easier than trying to explain it with words. 

 

So, the likely problem is immediately apparent and so is the solution...at least to me. Clearly it is not apparent to my customer and out of curiosity i wanted to see how you chaps get on. This isnt intended to mock my customer/anyone with the wrong answer or anything like that. The idea is to learn something as anyone with the wrong answer, or who is simply stumped by the problem, can see these symptoms in an engine down the track and have the answer provided here in their head.

 

The video shows a problem i am sure most of us have either had or seen at the field so knowing why might be helpful. 

 

Answers below, anyone with the right answer gets the smarty pants award ? 

 

 

 

[EarlyBird]

Fuel tank is above the centre of the carb.

[John Stainforth]

Air intake too close to firewall?

[Jon H]

Ok so perhaps not as obvious as i thought. Which is a good thing in many respects as we can narrow down our options. 

 

Early bird is right, Fuel tank placement is very important (call me a broken record) but usually it will only manifest itself once the engine is running and flying. It should generally not impact initial start up. Its tricky to see where they have it on the bench but i dont think its excessively high. 

 

Air intake. Quite right John, its very close to the backboard of the bench there and not at all recommended. Again, though, this will manifest itself as a problem only once the engine is running/in the air so its not our start up issue. 

 

Keep the guesses coming. 

[Don Fry]

No fuel in the engine

[J D 8]

  Throttle and/or needle valve not open enough for it to run, just getting enough fuel for a burp after a bit of spinning.

[Bruce Collinson]

No air pressure getting into tank as it's screened from the propwash?

 

I give in.

 

BTC

[Nigel R]

using one of them darnfangled on board glow drivers?

 

[Martin Harris - Moderator]

Low end needle screwed in too far?

I would recommend supporting the needle extension too. 

[Denis Watkins]

Vertical Silencer

Filling up, blocking outlet

[Chris Walby]

Fuel tank is too low as its only sucking fuel up the when the throttle is shut, then fires but its not running long enough to keep pulling the fuel through. 

 

Hence the immediate stopping after it starts. 

 

+ all the other things above

+ just put it in a model and give it a good thrashing with the tank in the right place!

 

 

Edited November 8, 2021 by Chris Walby

[EarlyBird]

Prop is too small or too light.

[Don Fry]

7 minutes ago, EarlyBird said:

Prop is too small or too light.

I wondered that, can’t get an eyeball on it, but it don’t look big.

 

Jon, can you give an explanation why the silencer close to the firewall is not good to go, and an indication as to an acceptable distance.
Winter build, 180, will be tight to the firewall, but I can sort it if I know where it has to go.

Edited November 8, 2021 by Don Fry
Spells

[Jon H]

 

Nice to see everyone enjoying the game ? 

 

Tank pressure and propwash. Again, this would only manifest in flight or after a short period of running. An engine loosing its tune in flight but running well on the ground would be a prime example of this. 

 

On board glow. Well it fired so we can assume glow is good. The plug might be in bad shape and it might not run well, but its firing well enough to get a start so i would rule this out for now. If the engine dies when glow power is removed this could point to a plug issue but not always. 

 

Vertical exhaust. If the exhaust was full i would expect a shower of goo when the engine did fire up. I would also expect lots a banging as it pre ignites/hyro locks. Flooded exhausts are a big problem on 2 strokes for sure. 

 

Tank too low. Again this is unlikely to prevent the engine from starting. It might throttle badly, or not hold full power, but it should at least start. A clear symptom here would fuel always flowing back into the fuel tank. 

 

Prop size. This too would not prevent the engine from starting. It might idle badly, thrash itself to death at full power, but it should not prevent the engine starting. 

 

 

So Martin wins the full smarty pants award with Don and JD8 getting honourable mentions. 

 

One thing that seems fairly clear in the replies and a few txt's i got (unless i am misunderstanding) is much diagnosis seems to be based on what can be seen rather than what can be heard. Listening to the engine is key to understanding what is wrong. 

 

When he starts cranking there is no fire for a long time. Glow engines need fuel, glow and compression to fire so one or more are missing to get no fire. The note changes after a very sort time with more of a chuffing sound coming from the engine. This sound is the throttle being opened to more than about 1/3 throttle. Watching the video carefully you can see the throttle open, and then close again. As it closes, the engine starts to fire. 

 

Why is this? When the throttle is opened the slow running needle is opened too and this allows more fuel into the engine. But, as the throttle is wide open we are still very lean and it wont fire. When he throttles back the amount of air reduces and the unburned fuel that has been drawn into the engine accumulates to a point where it ignites with this reduction in air giving a weak but combustible mixture. The engine runs until the fuel is exhausted, and then stops. 

 

Clues that it is a lean cut. Again, sound is the key. Ignition has stopped but the engine is still turning over due to its momentum and it runs down slowly. A rich cut will generally stop more or less dead and then often kick backwards giving a chuff of fuel out of the carb. Also apparent is the very soft and smooth engine note. Its brief, but the exhaust note is smooth and revs climb to a peak before flame out and run down just as you would expect if you pinched the fuel line on an idling engine. 

 

All of the above points to a lean slow run mixture.

 

This can be proven again by opening to full throttle and heavily priming the engine with a finger over the carb. Throttle back to idle, flip over a few times to clear most of it and then go for a start. If it fires right up and stops you again have your answer. 

 

Causes? Slow run needle too lean, blockage in the carb, main needle closed. 

 

We can probably ignore the main needle as the engine fired so some fuel is getting through. This leaves us only two things to check with the slow run needle being the first one to try. Open half a turn, see where you are. No joy? go another half and just keep going until something happens. Dont worry about going too far. Most glow engines will gladly start when rich so once you get it going tune up the main needle, then the slow run and you will be off to the races. 

 

I hope this gives a bit of an insight into how you can trouble shoot just by listening to the engine, understanding what all the little noises mean, and the clues they give regarding the problem and how to solve it. In my case, i did all the above diagnosis and knew the cause of the problem almost before the video ended and instructed the customer on how to fix it. But given the handy video i thought it might make a useful learning tool and thought i would give this group game a try as i have seen over the years that folk really struggle with engines that will not start at all. All the clues are there as to why and i hope this gives a few pointers people find helpful.

 

Let me know if it was of any use. 

[Martin McIntosh]

I bought a couple of YS motors, virtually unrun and going very cheap because the owners could not start them. They had mistakenly opened the idle needle by about 3 turns instead of the recommended 1 (air bleed carbs) so no chance of them running since there is zero fuel pressure at idle. Thank you very much for brand new half price engines.

[Don Fry]

Jon, why is the silencer close to the firewall bad, and what is the minimum distance. My winter build, 180 powered, is tight, as designed. Can be altered at this stage.