Laser 150 V TWIN REBUILD

[TartanMac]

Posted by Ron Gray on 30/11/2017 17:33:19:

Jon told me off for running my 160v at too low an idle but I’ve worked on the basis that as long as the ‘plane sits still at tickover then it’s ok, which just happens to be about 1900. Mind you I have got the wheels on a fairly snug fit which also helps on hot landings!

It does sound really cool though at low revs does'nt it. Even at the 1,800-2,000 sounds amazing. Mine does struggle at 1,400 you can feel through the bench every second firing on one of the cylinders it struggles to get over TDC. But it is nice and smooth higher up 1,800-2,000.

I was going to practice hand starting it today but my AA battery went flat. I did manage to hand start it but it ran backwards. Now I have the needles correct I will learn how heavy to choke it so I can throw it on compression and have it fire. When I did that it did not take much to get it to fire in terms of how hard to throw the prop but it took a good bit of fuel in the cylinder to get it to fire up. I would like it if I did not need a starter as I can paint my spinner the same as my aeroplane.

Ron I used to fly at an old coal mine that was shut down before I joined a club.They had a nice big concrete strip like yours. I had a hanger 9 Cap 232 I thought I was going slow then I touched down and man it just kept running down the damn runway till the end. I get what you mean about the wheels being nipped up. I think it is quite difficult on concrete/tarmac on grass your plane slows nice and quick and you don't need to go round in circles before take off. A guy at the club I was at was selling me an aeroplane and he was showing me his 50cc Texan and he told me he used Toe in angle on his wheels to act as a brake. In or out I cannot remember but pushing it on the ground you could feel it had good resistance. He did say it made a difference. Just wondering Ron some people at my old club had a setting on there TX for a high idle when flying and a low idle for landing do you just run 1,900 rpm idle all the time ? that is what I was planing as I only have a DX6I no high idle option.

[Denis Watkins]

Don't get too low on idle TM

You have differing inertia on the motor and tank, in the turn

A roll etc, and continually change in fuel level.

Cold days, warm days?

So the idle is a compromise with proven reliability at the stated rpm

[TartanMac]

Posted by Denis Watkins on 30/11/2017 18:39:29:

Don't get too low on idle TM

You have differing inertia on the motor and tank, in the turn

A roll etc, and continually change in fuel level.

Cold days, warm days?

So the idle is a compromise with proven reliability at the stated rpm

Yeah should have explained I was thinking using 1,800 for landing and cruising around and say 2,200-2,400 when really throwing it around and going to idle at the same time.

[Ron Gray]

@TartanMac - I have a separate switch for my throttle that I can activate to lower idle revs or run higher and I tend to use that on most of my IC planes. This means that I can fly around with no fear of cutting out but bring it into a landing under lower revs. With the 160v I haven’t needed to run it at a higher idle when flying but with my only 2 stroke glow, a Weston UK 52, I do use that switch as I do on a couple of my gassers. Funnily enough my DLE 55s do not need activation of the switch as they tend to be very reliable at all revs!

Toe in or toe out would also work as a brake but I wouldn’t use toe in as that could exasperate turning in / ground loops.

[Jon H]

a small o ring or thin slice of fuel tube squished between the wheel and the u/c leg is an easy way to add some rolling resistance. I will be adding some to my stampe over the winter as its currently got brass bushings running on steel axles which are all nicely oiled. Its not too bad on grass but on hard stuff it will never stop rolling!

Anyway, if you set 1800 as an idle it should be safe for the whole flight. Rons ground idle/flight idle is a good idea if you have the option but if not then don't worry

[TartanMac]

Well I ran my 1.50V again to try out the muffler. The end cap flew off the last time and I found the threads are shot and there is a crack in the piece it screws into so I tried epoxy it lasted 5 seconds. I will try and solder it I got some 450F stuff and used it on a Weston UK headed that had a crack right at the start of the pipe.

But I ran the engine anyway to practice tuning it, and have it down I think the main needles are a little vague and don't change top end much but I found that once I get them set the low end is fairly easy to set up both cylinders seem to like 3 clicks rich from when it just starts to surge and quit on quick throttle response. When I click them in leaner the engine will run at 1,900 rpm with the throttle pulled right back. And slowly wants to die. And also will not give good response time this engine sound way bigger than 25cc with the exhaust plate removed only one of them came off and I could not hear the other cylinder by listening to it I should have stood 4-5ft away so you could hear it a bit better it sounds very grizzly.

 

Edited By TartanMac on 01/02/2018 20:50:08

[TartanMac]

I figured it out easier than I thought.

Edited By TartanMac on 01/02/2018 20:49:42

[Jon H]

nice! time to get it in the air

[TartanMac]

Well I took the front housing back off the engine to take the size of the front bearing to order a rubber sealed one and get some new silicone high temp sealer and found that my sealant was no longer there and had come off. No big deal I thought at least I know where some of the oil came from.

But then I took the crank out and noticed the crank pin has been very badly scratched by the rods big ends and found that the bushings are not smooth either. I was wondering if there is a fix for this. I remember polishing up the crank pin with 2000 grit but did not touch the rod bushing. Will I need to replace the bronze bushings ? I have a Q40 Irvine that needs the rod bushing replaced and a few other things on a list for when I can get to a family members work shop. But he can only get time off once a fortnight and not every fortnight is he gonna want to be there. But I can put it on the list as I have not got the aeroplane started for this engine yet. I will put photos up soon. I took the heads and cylinder off and they look fine the pistons move nicely in the cylinder now and the heads look great with a light yellow golden colour but no carbon.

Can I just run some 1200 grit round the inside of the rods bushing and clean up the pin ? I have only run 4 tanks I think and it has scratched up already.

[Jon H]

if there are scratches then its likely some foreign matter got into the engine. Could any of the shot blasting media you used have found its way inside? that or the conrods were put in backwards but i think we discussed that at the time?

Changing the bushes is not really an option so your plan for some gentle wet/dry treatment is really the only option at this point.

[TartanMac]

I don't think there could have been any media in there as I washed it in old glow fuel then put it in the ultra sonic cleaner and refreshed the water till nothing was coming off it. I can remember that the pin had some scores on it when I stripped it but not that bad really. There is some grey gunge in one of the followers where the push rod fits in so maybe there was some residue but the little ends are fine. I will strip it right down again clean it and just do the wet /dry on the pin and bushes like you say then replace the bearing and seal the front housing and cylinder bases. I suppose when the pin and rods wear out I will hear it knocking like my irvine.

I ran it on 10% for 1/2 a tank and found I could hand start it from cold very easy and got 200 rpm more 8,700 on a mejzlik 16x8 but the low end needles were a little tricky to setup and it did not want to quit straight away kept idling at 1,100-1,200. Also at a prolonged idle (1,800 rpm) the left cylinder dropped off. I think maybe the Irvine fuel runs the cylinder cooler with 10%. With 5% Laser it was difficult to hand start from dead cold but tuned better and was more reliable at low revs started easy by hand with just slight temp in it. I think with fresh 5% fuel I will be able to hand start it to an idle of 2,000 rpm easy

I fixed the exhaust also there was a metal piece in the muffler rafting around with the threads on it the screw caught the threads and it torque up nicely.

After running this engine through a few tanks now I got used to it and it is a super engine I am very happy and hopefully the crank pin and rod issue get sorted easy. This is my favourite engine now and I prefer 2 strokes mainly but this is pretty special.

[TartanMac]

For some reason these photos did not turn out well but you can see the very end of the crank pin is polished shiny and the rest is scuffed up the rod is the same.

I put a pic of 2 cranks together to show how compact the V Twin crank is. The black and polished crank next to it is a Moki 61LS 2 stroke crank amazing really that it is that small you would not think it is a 25cc crank. I suppose this is another reason there is so little vibration for its capacity such a small throw and small counter weight. I realised there is not many pics of the Laser engines in pieces especially the V twins. So I thought I would put it up as it is pretty interesting.

[Jon H]

not sure if its the focus but im struggling to see anything wrong. is the dark line on the pin a scratch?

[TartanMac]

The focus is bad it is hard to get a good shot of it I will try again with better light. The dark line actually does not feel like a scratch and that line sits right in the centre of the left cylinders rod if you were looking from the rear of the engine. Everything left of that line is scuffed up and just a small amount right of it is scuffed the very end of it is still polished. The inside of the rod bushing if I take a small Allen key and run it across it I can feel the ridges.

[TartanMac]

I don't think I can get the rod pic any better but I think you can see the pin

[Jon H]

ok i see.

Other than polishing the parts again there is not much you can do. To be honest i wouldnt worry too much as there is no pickup and that is the only real show stopper.

Just make sure the rods go in with their flat faces together and it will be fine

[onetenor]

Polish the pin and re bush close to finished size then ream and hand lap to fit If there is an.oil hole in the bush make sure it lines up with the hole in the rod. Presuming of course you have access to workshop facilities/ A lathe at least. And wash out the engine thoroughly again removing any sludge which will contain metal. Hence the grey colour.Also make sure that the pin is parallel .

Edited By onetenor on 05/02/2018 15:46:48

[Jon H]

Dont go mad. In those days the cranks were EN24 but were not hardened so were not as hard wearing as they are now so they will mark up more than is accepted today. Since 92 we hardened all the cranks and made them from EN36 which is even tougher.

[TartanMac]

Thanks for the info guys I think the gunge is from the cylinders as I did not hone them and they were not clean when I went round them very very lightly the paper was black and brown coloured from the liners. But they are very nice looking now apart from some orange from light corrosion which I felt turning it over after running that 10% Irvine fuel. I thought it might well be the media from blasting it but there is no sign of it in the crank case but the mess in the cam box I cannot actually feel it on my fingers so I'm guessing it is from the cylinders the cams have a polished finnish now and don't have a dip in them I think the rest of the engine is fine. But it does look pretty dirty.

I had a Picco 28 P3 engine in a Hobao Hyper ST Pro 1/8 scale race truck Brand new just run in and I took it to an old coal mine. I put a new air filter on it but pinched the bottom with the tie wrap so there was a gap coal dust went in one tank and the engine was ruined. When you mentioned the blasting media Jon I got flash backs.

[TartanMac]

Just wondering if anyone has a recommendation for a sealer as that stuff I used last time did not seem to stick well in the crankcase environment with oil and fuel it came of very easy. I used it on an inlet manifold on my Enya and it stuck and sealed way better but it is on the outside of the carb not inside a crankcase.

I was going to buy the black Visbella silicone stuff but there is quite a few options.

[TartanMac]

I was thinking about using epoxy as I used it on an exhaust before and it sealed well.

[ken anderson.]

give clear silicone(fish tank quality) a go, you'll find it does the job well...no problems getting it off should you need to. I've used it for exhaust gaskets on 2 stokes...last I bought was £5.00 for a small tube

ken Anderson...ne...1..... gasket dept.

[Jon H]

i used loctite 595 here at the factory. it stinks though

[TartanMac]

Well after a good wait I got what I needed. I looked around loctites site maybe I was on the wrong part of it or wrong site but they had very poor descriptions for the wide variety of choice between there products. I ended up going to buy 620 but after being on ebay found 641. I was looking at 574 sealant but the price and the fact the 595 says it is flexible and also your recommendation Jon I went for the 595.

I was wondering about the sealer and thought is it better to put it on and just torque it up straight away or should I partially torque it till it just starts to set then torque it right up ? I was going to take the inner seal off the bearing but was wondering what your recommendation for that would be Jon as I have removed factory fitted bearings off a few engines that had both seals fitted.

[Jon H]

yup, rear seal off the bearing and give it the full beans with the torque