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Laser Engines - Technical questions

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Rocker29/05/2020 09:17:32
359 forum posts

Hi I have a Laser 80 and it is not running right. It OK at full throttle but erratic at mid range .I retune the slow running needle valve like Jon show in he's video ,it is a bit better but just can not get it to run right in the mid range .I then look at the valve clearances and the inlet valve was fine but the exhaust valve had no clearance what's so ever .I have now adjusted the valve clearance on both valve to so the 0.004 feeler gauge goes through and the 0.10 does not .Due to our club field still being closed ( tell me about it ) I can not check it in flight .It seems to run fine on the ground .Would the exhaust valve having no clearance make much difference to the mid range running of the engine or am I just hoping it did ?

ken anderson.29/05/2020 09:26:09
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8858 forum posts
820 photos

hello rocker,Jon is the man...but I think you may have found and solved the problem your self.....if the exhaust valve had no clearance imagine when it was hot it wouldn't be able to function correct(close/seal)….see what the main man says.

ken anderson...ne..1...…. E/V dept.

Jon - Laser Engines29/05/2020 09:55:52
5750 forum posts
275 photos

Hi Rocker

The basics:

What fuel, prop, plug and top end RPM?

Valve clearance can have an impact but usually its small unless they are massively wide. My quick and dirty method of setting valves is to tighten until no clearance and they slacken the screw about 1/8 turn. Its not perfect but works well enough if you are in the field or dont have all the tools to hand. frankly, its accurate enough for our purposes anyway so dont loose too much sleep over a thou or 2 of valve clearance.

bert baker29/05/2020 10:41:17
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1649 forum posts
337 photos

Get a new carb,,

might be unmetered air getting in

Rocker29/05/2020 10:52:13
359 forum posts

Hi Jon,

I have the Laser 80 in a Seagull Fokker C1 ,which is basically a Bowers Flybaby in disguise. The exhaust valve had no clearance what so ever but the inlet was fine .I have now adjusted the valves to 0.004 .I am using Model Tec Laser fuel and I have a 14x7 prop on it . Has I said I have adjusted the slow running needle valve like you showed in the video and it was a lot better but still ran a bit erratic at mid range .Then I discover the exhaust valve had no clearance it was tight up against the rocker so I adjusted it to 0.004 .It seems better but I have not try it in flight yet .Would the tight exhaust valve be the cause of it running a bi erratic at mid range ?

Rocker29/05/2020 10:52:17
359 forum posts

Hi Jon,

I have the Laser 80 in a Seagull Fokker C1 ,which is basically a Bowers Flybaby in disguise. The exhaust valve had no clearance what so ever but the inlet was fine .I have now adjusted the valves to 0.004 .I am using Model Tec Laser fuel and I have a 14x7 prop on it . Has I said I have adjusted the slow running needle valve like you showed in the video and it was a lot better but still ran a bit erratic at mid range .Then I discover the exhaust valve had no clearance it was tight up against the rocker so I adjusted it to 0.004 .It seems better but I have not try it in flight yet .Would the tight exhaust valve be the cause of it running a bit erratic at mid range ?

Edited By Rocker on 29/05/2020 10:53:14

Jon - Laser Engines29/05/2020 11:47:39
5750 forum posts
275 photos
Posted by bert baker on 29/05/2020 10:41:17:

Get a new carb,,

might be unmetered air getting in

Nothing personal but i always see this advice and totally disagree with it. In 25 years i have only ever had to replace 2 carbs. 1 due to crash damage and 1 that was worn out so just replacing the carb as a first port of call is a little premature. Its also not very cost effective as 90% of erratic running problems come down to either poor fuel, poor plug, or bad tuning. While its true air leaks can cause problems its rare that an entire carb need to be replaced in order to fix it.

Rocker, the valve clearance is not critical so i doubt it is the cause of the problem. My suspicions are still plug/tuning.

When you say you set the engine up according to my video, how far did you go leaning off the slow run? In my experience most chicken out early so its possible you have a little more leaning to do.

If in doubt, shoot a video (without the camera in the prop wash!) and upload it you youtube as an unlisted video. You can then post the link here and we can have a listen

cymaz29/05/2020 11:57:38
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9597 forum posts
1267 photos

If I have any run issues with a glow the first thing is to toss the old plug and put on a new one.

Edited By cymaz on 29/05/2020 11:57:58

tigerman29/05/2020 13:06:16
267 forum posts
1 photos

Hi Jon ,

Tried to down load the video but failed .It would not download into my album so I could not post it .It was only a few seconds long .Do not know what went wrong

cymaz29/05/2020 13:11:30
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9597 forum posts
1267 photos

Load it onto youtube then use the YouTube icon above in the icon / menu bar.

P.S. you will need a yt account if you haven’t got one already..

Edited By cymaz on 29/05/2020 13:12:29

bert baker29/05/2020 21:17:21
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1649 forum posts
337 photos

Be quicker to pop the engine in the post

Jon had his fingers on my 180 last year

was quick turn around and very pleased 😀

tigerman02/06/2020 15:25:25
267 forum posts
1 photos

Hi Jon I did what you surgested about leaning the slow running needle more and BINGO .the Laser 80 runs has sweet has a nut again At low rev middle range and at full chat .Thanks

Rocker02/06/2020 18:54:44
359 forum posts

Just a quick qustion .Will the Laser 180 fly the Seagull Hurricane 2083 mm ?

Tim Flyer02/06/2020 20:22:43
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1411 forum posts
255 photos

Hi Rocker yes it will with plenty of power although there are a number of issues with the plane. I have one powered by the Laser 180 and there is a quite detailed thread on it . Which I will link

https://www.modelflying.co.uk/forums/postings.asp?th=140639&p=1

 

a lot of my assembly notes are on this thread

https://www.modelflying.co.uk/forums/postings.asp?th=124909&p=2

Edited By Tim Flyer on 02/06/2020 20:27:18

Edited By Tim Flyer on 02/06/2020 20:29:15

Jon - Laser Engines02/06/2020 21:51:10
5750 forum posts
275 photos
Posted by Rocker on 02/06/2020 18:54:44:

Just a quick qustion .Will the Laser 180 fly the Seagull Hurricane 2083 mm ?

It sure will but as Tim says there are other issues to consider.

Again the threads he linked show the full story but the short version is we have two of these powered by laser 180's and while both fly fine they are a right faff to land. I flew Tim's about 3 or 4 times i think but must have in excess of 20 landings on Chris's model as i just kept shooting approaches with it. If we assume 25 landings total over the 2 models i think only 4 were of a standard i would consider acceptable.

What i cant work out is why its so hard to get them right. Approaches feel lovely and stable yet the flare/touchdown is a nightmare. At some stage we are going to try and get all 3 of us together and work out exactly what is going on.

Unless we can work out a very specific recipe of balance/control throws etc then it might be a bit of a struggle.

David Davis08/06/2020 09:53:57
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3860 forum posts
741 photos

I flew the Big Guff for the first time yesterday. The model weighs 8lbs 9ozs but there is ten square feet of wing area so I was flying it around on a slow tick over most of the time. The model is fitted with a Laser 70, I am using 5% nitro, 15% oil fuel and a 13x6 prop. I have a 13x4 prop. Would that suit the model better?

one mightily relieved pilot.jpg

Jon - Laser Engines08/06/2020 11:08:18
5750 forum posts
275 photos

It will rev like mad on 13x4. Try 14x5 or 15x5 if you can find one. 15x4 would also work, i think even 16x4 if it exists.

Given the nature of the model you can really load the engine up with whatever you like. As its going to float around at low power the engine will not be stressed that much.

I use a 15x5 turnigy wooden prop on my saito 45 and the poor little thing can only manage about 6000rpm. As i only need about 4500 to fly it works out well. The turnigy prop im using does fun fast though so its probably equivalent to 14x5 from another brand.

David Davis08/06/2020 11:17:13
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3860 forum posts
741 photos

Amongst my collection Jon i have a 14x6, a 15x6 wood and a 16x4 wide APC. I'll try the 16x4 on Wernesday.

 

Edited By David Davis on 08/06/2020 11:17:35

Jon - Laser Engines08/06/2020 11:39:12
5750 forum posts
275 photos

yea i would give give the 16x4w a go. I doubt it will rev much but that is hardly going to matter. It might allow you to use slightly higher rpm in flight, which is good for the engine, without gaining excessive speed.

Frank Skilbeck08/06/2020 11:44:39
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4929 forum posts
114 photos

As I noted earlier I have a Ben Buckle Majestic Major with a Laser 62 and 15 x 4 prop, pretty much perfect.

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