Laser Engines - Technical questions

[Frank Skilbeck]

Last year I acquired a 2nd hand Laser 150, the version with the vertical plug and Irvine carb, it runs great but spews oil out of the front bearing. I remember the seller telling me the bearings had been replaced but I think the front bearing must be faulty. Before I strip the engine down is there anything else that could cause this to happen?

Lastly any recommendations on replacement bearings.

Thanks.

[Martin McIntosh]

Blocked crankcase breather maybe?

[Jon H]

The usual suspects are blocked breather, wrong bearing, failed bearing, dead rings, scored cylinder, bent crankshaft.

Usually very oily engines are suffering in the ring/cylinder department and the crankcase pressure increases significantly due to a mix of additional blow by and the hydraulic action of the sheer amount of oil blocking the breather. This added pressure means the air in the crankcase being compressed by the falling piston will escape wherever it can.

if you want to change the bearings the front is a 6001-2rs with the rear seal removed. i would clock the crank to see if its straight (a bent one makes bearings act like a wobble pump) and see if the rings/bore are any good

[bert baker]

I would send it to Jon to service.

He did my 180 a short while ago,

Very pleased with service and price

Bert

[Edgeflyer]

I am working on an elderly and rather neglected Laser 75. I know these are no longer supported but it was cheap and I think worth some work I got the thing mostly apart with a view to changing the bearings and cleaning it up. The front bearing is a little rough but after flushing out some of the old gum it spins quite freely. As the prop driver is refusing to part company I either have to buy a puller or I am wondering whether just to reassemble and see how it runs. Similarly the cam shaft bearing spins nicely now, but there is a little play. How important is this? Should I change it and if so how do you extract the cam shaft with its pinion?

[Martin Harris - Moderator]

Posted by Phil B on 26/10/2019 14:29:13:

Similarly the cam shaft bearing spins nicely now, but there is a little play. How important is this? Should I change it and if so how do you extract the cam shaft with its pinion?

How much is a little? A bearing with no play won't work!

Unless Jon disagrees, I would change it if there are any traces of visible wear on the balls or tracks or hint of roughness. Except if it's a non-standard size, for what one would cost from a bearing specialist, there's little financial reason to hold back.

Edited By Martin Harris on 26/10/2019 16:47:04

[Edgeflyer]

Jon, Can you advise please?

The cost of bearings is negligible but what bothers me is getting them out. Particularly the rear one that supports the cam gear. There is play in it, a slight wobble, but I don't want to damage the gear tapping it out.

Thanks Phil

[Don Fry]

Brutal, does it start? Take the glow plug out, open the main needle a long way past rich, give it a blast on an electric starter, connected to fuel for a 30 second or so. Then plug back in, return to proper settings, and ?

[Frank Skilbeck]

Posted by Frank Skilbeck on 25/10/2019 13:40:15:

Last year I acquired a 2nd hand Laser 150, the version with the vertical plug and Irvine carb, it runs great but spews oil out of the front bearing. I remember the seller telling me the bearings had been replaced but I think the front bearing must be faulty. Before I strip the engine down is there anything else that could cause this to happen?

Lastly any recommendations on replacement bearings.

Thanks.

OK, I've removed the back plate and front housing, breather is clear, bore and piston look good (compression is excellent) and all parts were lightly oiled and oil was clean. Going to pull the prop hub off later today and replace the bearings, which is best for the front bearing, metal or rubber seal?

Also going to do an old 62 I acquired up that was all gummed up with notchy bearings, will then bring my Laser collection to 5

[Jon H]

Sorry chaps i missed a bunch of posts here.

Phil, does the engine run? if not or its got no compression then its a waste of time trying to fix the bearings. Put it back together, run it for a few minutes to see if its dead. If not then change the bearings. Clearly if the bearings are totally ruined then dont do that in case they fail.

To get the bearings out you really need a press to be honest. If you are gentle then a vice will do. When you press the pinion out you might find the bearing comes with it, if so your options are limited as getting it off is a pain.

The crank bearings are easier but you still need a press or a puller to get the prop driver off.

Frank, go for a rubber seal bearing but remove the rear seal otherwise they go rusty once the grease leaks out.

[Edgeflyer]

Jon, Thanks for the advice. Having got the bearings clean they seem free enough, so I will rebuild and do a test run before deciding what to do next.

[tigerman]

Need some hand help setting up my Laser 80 .I have a First World War model with a Laser 80 fitted and I like to fly it on half throttle ,here is my problem .I have tuned the needle valve to run at full throttle and it runs OK ,when I point the model up it is fine but when I fly it on half throttle in the air it splutters .So I tuned the Laser to run at half throttle and it fly OK untill you try to loop ,it will cut out when traveling upwards .When I landed the Laser was it was fine on half throttle but has soon has I point the nose up it cuts !!! It seems I can either run it on half throttle and not try to loop it or tune it to run on full throttle and at half throttle it will run rough If I tune the main needle to run at full throttle it will not run great at half throttle and if I tune it to run on half throttle it will not run with the nose point upwards HELP a first world war flying at full throttle looks terrible .I am running a 15/8 prop

[Alan Gorham_]

I would find it astonishing if your engine did not come with tuning instructions.

In those instructions I would hope there would be a section on tuning the low speed needle as this is your issue. The high speed needle is set (typically) at fully open throttle as it controls the fuel/air mixture until the throttle barrel is closed enough for the low speed needle to have the dominant effect.

You haven't mentioned what you have done with the low speed needle to set the mixture at low throttle settings...

[tigerman]

Simple answer to that is I have not touch the low speed needle .Looks like that is where the problem is .So if it runs OK at full throttle and seems to me to run a bit rich at half throttle does that mean I need to turn the slow running needle clockwise to get it to run at half throttle ?

[Alan Gorham_]

You tune the low speed needle at your intended idle speed, not half throttle. Otherwise your engine won't run well when you throttle back to land.

The sure-fire way to check your tuning at low throttle is to let the engine idle for 30s or so and then bang the throttle open. If the engine dies straight away then the low speed needle is too lean and needs screwing out a bit.

If the engine splutters and stumbles its way up to full throttle then the low speed needle is rich and needs screwing in.

You usually have to adjust the low speed needle in small increments.

Again, I'd bet this is in the engine instructions.

[J D 8]

And once you have the idle right you may have to readjust high end again, more so if low was well out to start.

[Edgeflyer]

Hi Jon,

I need some advice on reassembling my Laser 75 please.

I got a new replacement front end with crank and bearings which spin nicely. (thanks to Graham who found one in his spares box).

I need to know the timing settings. Do the cam timing dots point to each other at tdc, or point at the cam followers at tdc, or what?

Secondly the o rings on the ends of the push rod tubes are hard, so probably need replacing. Are they 7mm diameter or what?

Thirdly, the spray bar in the Carb. Does the fuel venturi slot point downwards, upwards, front or back?

I know I should have seen these points during dismantling, but hopefully you can put me right please.

Thanks Phil

[Chris Walby]

Tigerman,

My understanding from the manual, Jon and his Youtube video is:

1. Make sure everything else is correct (tank height, plumbing, throttle linkage etc)
2. Set engine low and top end needles to start off position (in manual), see PS at end of post
3. Start engine and warm up
4. Hold at full throttle and adjust for max top end revs
5. At tick over keep snapping the throttle open and adjust so pick up does not hesitate (lean side then back a bit)
6. Hold at full throttle and adjust for max top end revs
7. Go fly

You can repeat steps 4 to 6 as many times as you want, but I have been told I am wasting my time, fuel and wearing the engine out...

Next time you fly you might need to adjust the main needle (between summer/winter) but that is all. if it goes off song by a fair way, then something else is wrong!

Hope this helps

Base setting for an 80, main 2.5 turn out, slow needle 7 turns out as a starting point

Edited By Chris Walby on 06/11/2019 17:53:01

[Nigel Dell]

Posted by Phil B on 06/11/2019 17:09:36:

Hi Jon,

I need some advice on reassembling my Laser 75 please.

I got a new replacement front end with crank and bearings which spin nicely. (thanks to Graham who found one in his spares box).

I need to know the timing settings. Do the cam timing dots point to each other at tdc, or point at the cam followers at tdc, or what?

Secondly the o rings on the ends of the push rod tubes are hard, so probably need replacing. Are they 7mm diameter or what?

Thirdly, the spray bar in the Carb. Does the fuel venturi slot point downwards, upwards, front or back?

I know I should have seen these points during dismantling, but hopefully you can put me right please.

Thanks Phil

I am sure Jon will be along shortly to give you the answers but when I stripped my 90 years ago I asked Neil the same question about the cam timing and he told me the marks did not correspond with anything the timing had to be achieved with a protractor and inlet and exhaust opening in degrees before TDC as with most engines, easy to do if you have the figures, they escape me at the moment but are written down somewhere here!

[tigerman]

I believe Jon has done a video on how to set up the tick over on a Laser Engine, anyone know where I can find it ???

Edited By tigerman on 06/11/2019 20:51:44

[Gary Spicer 1]

I think this maybe it, a few post down on this page:

https://www.modelflying.co.uk/forums/postings.asp?th=122575

Edited By Gary Spicer 1 on 06/11/2019 21:19:31

[Don Fry]

Tigerman, Chris, a couple of posts up is spot on. I would say, at point 5, leave the engine to settle down to its diet of fuel before snapping the throttle open. So a rich condition, or a lean condition can develop. Perhaps 30 seconds to be sure. Tune as Chris suggests, and also Jon's set up, a few pages back, in response to your earlier problems

But you do not tune engines for mid range running. When you say it runs rough at half throttle, engines do sound different to flat out here. There are more missed beats. Is it threatening to cut? Does it answer the throttle correctly?

[tigerman]

Yes thanks everyone .I think between you I have found the problem .My main needle valve was over 3 turns out and my low running needle valve was only 5 1/2 turns out . I will make sure the carb is all clean out and reset it to what you have all said ie main needle valve 21/2 turns out and the slow running needle valve 7 turns out and once this rain has stop I go out and tweak it out like you have explained

[Jon H]

You guys have been busy...

Tigerman, 15x8 is very big for the 80 and on a WWI model i would use a finer pitch. 15x6 is safe all day long, 16x6 will be a similar load to the 15x8 but might work better than the 15x8.

Now, because you are running the engine in an essentially overloaded condition this means that the temperature inside the cylinder will skyrocket if you run it at full power for too long. This will make it sag/loose rpm but it does not mean its lean. Most likely you are taking too long with your tuning adjustments and the engine is heating up causing a loss of performance and forcing you to run rich.

I have a similar situation with my saito 45. Its running a huge 15x5 prop and only does 6000rpm flat out. I can use full throttle for no more than 10-15 seconds on the ground before it overheats so tuning must be done quite quickly. Again, this is internal cylinder temperature and not overall engine temperature. You cant use a thermometer, you just have to do it by ear.

Once the top end is out of the way you can deal with the slow run. As you have the engine running 'overloaded' you will need a rich slow run mixture to allow the engine to accelerate. This will result in poor mid range running. The solution is to lean the slow run, and then be much more gentle with the throttle. Set a 2 second throttle servo slow on the tx if you dont trust yourself to not firewall the engine in case of emergency.

This is also true with normal props. Its all about load, more load means more fuel is needed, less load means less fuel. Accelerating a heavy load prop takes more fuel than accelerating a light load prop. Equally, accelerating a heavy load slowly can use the same fuel/tuning as accelerating a light load quickly. f=ma and all that. So, snapping the throttle open is a good way to check the tune but, as with everything, its not a one size fits all solution and ultimately you just have to listen to your engine and understand what its trying to tell you.

Dont be frightened of your slow run needle. So many people never touch it and its a big mistake to ignore it as it meters all fuel flow below half throttle. Perhaps calling it an idle needle is the root of all this confusion? In any case 7 turns will do nothing more than get the engine started, and as its already running setting it to 7 turns wont help you. You have to tune it, listen, adjust, listen some more. Its not possible to set it up by numbers. 

 

Phil, stand in the naughty corner. Honestly, not marking the positions of all the parts before taking it to bits? Hang your head in shame

O rings are easy, BS008. I can send you some if you need them
Spray bar is easy, the opening should point down its throat towards the valve but sometimes it works better at a slight angle. You will need to play with it once the engine is running again.

Cams. There are no timing marks, i will see if i can get a picture uploaded. Until then, stay in the naughty corner

Edited By Jon - Laser Engines on 07/11/2019 10:14:13

[Jon H]

Set with the piston at TDC. Count teeth to ensure accuracy