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Laser 150 V TWIN REBUILD

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TartanMac20/09/2017 18:51:56
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I recently started putting together my old Laser 1.50 V Twin and realised I don't have a prop nut. I tried a 60 size 5/16 then a super tigre 90 and a saito 180 one with no luck does anyone know what the thread size is ?

Also the conrods have a step out on one side my guess is that it goes to the front as there is a small chamfer in the bushing but do both rods face the same way being the step and chamfer face the front on the crank ?

Jon - Laser Engines20/09/2017 19:36:56
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The thread should be 5/16x24 unf. I don't think we used the 3/8 thread on those. The conrods go with the two flat sides together though so that's easy

TartanMac21/09/2017 01:49:05
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Thanks for the help Jon. I fitted a 5/16 and it does fit the thread on the crank is a little damaged but once you get it past 1/4" or so it goes on easy. I was looking at both cylinders and found that one is different at the very bottom. One has been made thinner at the very bottom of the liner around 1/8" from the bottom it is turned down thinner I have no idea why that would be like that and am a little lost on which cylinder is on the right side looking from behind and which is the left side does that have any significance ?

My crankshaft has to be put in the front housing very square to slide through but once it is it does not go tight when pushed home is that ok ? Is there something I should do with it ?

One more thing I have fitted new reproduction piston rings how much running should I put through it to seat the rings and do I need to make the engine very rich due to 2 rings per piston.

Thanks for the help had this engine 7 years never run it because it was a mess but finally have it at a stage of just putting the parts together.

David Davis21/09/2017 03:09:15
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I've got one of these. I'm following this thread with interest.

laser 150 v twin in action (1).jpg

Phil 921/09/2017 06:40:38
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David that engine is wasted powering a workbench

Jon - Laser Engines21/09/2017 08:41:50
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The difference in the liners will be due to design changes over the years. Its possible the engine has had a new liner at some point in its life and i would not be concerned by it. The crank has likely got some corrosion or baked on oil on the front section which is making it hard to insert. Its also possible the bearing journal has worn if the rear bearing locked up and the crank spun in the bearing. Its not something that can be fixed and wont harm the engine now it has new bearings so again i wouldnt worry. 

Before you reassemble the engine i recommend you VERY GENTLY take some 400 grit wet/dry paper and give the inside of each liner a little tickle. Use a good blob of oil and rotate the liner as you run the paper up and down. If you do it right you should end up with a light crosshatch pattern and smooth surface inside. If you dont want to risk damaging it, or the liners look in good condition anyway then dont worry about it.

As for running in i wouldnt be too worried. Use plenty of oil when rebuilding it and then fire it up quite rich and run for 3 minutes or so at about 5000 revs. Then open it to full chat, lean it off for max revs then come back about 1/4 turn. Run it at those needle settings up and down the rev range for about 5 minutes then turn it off and let it cool. Another 5 minute run like that with cooling after and you are going to be in pretty good shape so lean it off for max performance and just go fly it. Dont use full power for more than about 15 seconds in a burst until you have an hour or so in the air.

a 16x8 prop will be a good place to start

Did you remove the cams by the way?

 

 

Edited By Jon Harper - Laser Engines on 21/09/2017 08:43:54

TartanMac21/09/2017 09:51:42
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Yes I removed the cams I will need to retime the engine which I will need help with also. From memory the cam teeth I think are in 20 degree increments. I did lay out the cams to replace them in the right holes also the cam followers but I don't know the timing. I lost the bolts for the backplate but I'm sure they are the same size as the front housing and exhaust bolts so should be able to find the size online due to outer size and inner thread diameter. I did that with the head bolts and from memory I think it was BA6 thread. I only have one of the original head bolts with the hole drilled in it to bolt the rocker cover on so will probably run without them I take it I don't need them on for pressure or anything ?

The cams are in great shape the carbs are tight they give a binding grey paste when oiled I was going to Polish the barrels to reduce it as it worries me abit I don't want it pulling that into the engine.

I think your right about the cylinder from memory I recall having to grind the valves on one cylinder a fair bit more than the other to get it to seal using car plan paint rubbing compound I think it might have a slight warp in it as I read about someone having a problem not being able to get the valve to seal on a laser years ago and it was suggested to them. I have this engine without a spec of dirt on it now and able to see how well made it is.

I took a Saito 180 apart to replace bearings and clean and honestly don't look at Saitos the same after it. They are well made but my old 150 V with the heads and case cleaned up are more impressive. For a start they have valve seats and big end bushes lol but they are cut and seated incredibly accurately in comparison to my enya 1.20.

I will get shot down for mentioning this but the heads and case were very badly corroded to the point there is pitting on the head and case. So I cleaned them and then dipped them in a solution of water and a bit of caustic soda. I did this to a Weston UK head to take the anodized Finnish off which it did only around 5 microns. 20-30 seconds and it cleaned the entire head but can still see the tooling marks of manufacturing then I sand blasted it with my mini compressor with grit that also does not affect tolerences. Looks amazingly clean I will post pics later

When I pulled the heads out the solution I put them straight in the ultrasonic cleaner with boiling water in it it took the black and yellow colour off and when I pulled it out it was evenly covered in corrosion pure chalk white wish I got a photo.

TartanMac21/09/2017 10:04:53
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Hopefully mine is on the bench soon also David great pic. Its amazing that all modellers have different engines but they all get tested on the black and decker work bench lol.

Jon - Laser Engines21/09/2017 13:42:54
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The bolts are all 4ba and i can send you some backplate bolts if you need them. I dont have any head bolts left though im afraid.

Dont worry about the sand blasting. When new the engine would have had a shot blasted finish anyway and we still blast all of the engines to this day.

The troublesome valve could have been partly caused by wear on the face as the valves as they were not hardened in those days and the bronze seat eats them. We now harden the valve and have done away with the bronze seat as the new grade of ali we use for the heads works just fine.

David Davis21/09/2017 14:37:27
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Can we fit modern valves to the old V150 Jon?

Jon - Laser Engines21/09/2017 15:08:44
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Posted by David Davis on 21/09/2017 14:37:27:

Can we fit modern valves to the old V150 Jon?

Nope, as they are hard now they will eat the rockers, collets and collet retainers. They were also a slightly different design.

Current engines have fully hardened valve gear as it was found the early design would wear out after 20 or 30 years and we decided that wasn't good enough

TartanMac21/09/2017 23:42:56
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Just wondering is it stainless the valves are made of ?

Jon - Laser Engines22/09/2017 13:31:30
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They are now, not sure about the originals

TartanMac28/09/2017 18:53:28
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This is my cards one is in original state the other I cleaned up I used wet and dry on the polished alloy and my mini sand blaster on the casting and a bit of brass Polish missed the low speed needle.
TartanMac28/09/2017 19:07:23
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228 forum posts
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Laser carbs

TartanMac28/09/2017 22:17:27
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228 forum posts
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V Twin rodsLaser 150V caseLaser 150 V Twin case

This is the case I got some oil on it as one of the pins was not free took it apart after I oiled it and found a little castor I blasted this with my mini sand blaster all the blasting was done with 220 grit aluminium oxide it is the only media fine enough to get through the gun. I don't recommend buying a mini compressor for this work the cup is too small and not enough volume in the compressor tank it gets a little patchy too but better than it was by a mile.

Jon - Laser Engines28/09/2017 22:49:33
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Looks fine to me thumbs up

TartanMac29/09/2017 01:01:07
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If you click the photo to zoom it up you can see the corrosion had eaten some of the finning but apart from that the heads came out very well. I just have to shine up a few more things and will be ready to bolt on the rest. I think I might try and hone the cylinders. A family member told me he has a small honer for his old bridgeport mill today. Is there anything I should know about using one of those Jon you mentioned 400 grit I take it they have stones on the hone tools ?

Corrosion on head

Top of head laser

Laser combustion chamber

Jon - Laser Engines29/09/2017 08:20:55
3920 forum posts
151 photos

the 400 grit and oil is the poor mans hone i guess you could say. It is also likely to be a little less savage which is good as you are only looking for a polish in this instance. I would be very wary of the hone as any mistakes will destroy the liner and i cant replace it. If you have a softer brush hone of the right size that would work well

TartanMac03/10/2017 01:00:56
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228 forum posts
142 photos

V Twin cooling fins

Polished up the cooling fins it actually took quite a long time doing it by hand but well worth it. Jon I went round the cylinders with 400 grit but I could see the original honing marks and was not sure what it should look like once done so I done 2 rotations of both cylinders 45 degree cross hatch then decided to leave it I don't want to ruin it.

I freed up the carbs also that was tricky too, still get a little grey colour on the barrel with oil but it is very very little now.

Something about a V shape engine Just looks impressive. It is coming along nicely.

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