Anthony Scott 2 Posted July 16 Share Posted July 16 I bought my Laser 150 NIB in 2017, from 2019 it has been flown frequently in a 82" Seagull Spacewalker. I have never been able to get more than 7400 rpm, on Laser 5% & a Graupner 16*8 & using an OSF plug. Last weekend I had to abort a take off because of a loss of power on the 1st flight of the day. On running the engine in the pits the rpm audibly fell & the engine began hunting gently. I used a tacho on the next start & saw that the RPM was 7400 but that quickly by 1000 rpm & the engine was hot. Another start, with a richer mix saw the rpm fall from 6000 to 4300 with more hunting. When I took the valve cover off an inordinate quantity of clean oil flowed out. The engine has never suffered a crash, has excellent compression & the valve clearances are as specified. Ideas please. Tony Quote Link to comment Share on other sites More sharing options...
Don Fry Posted July 16 Share Posted July 16 Check the plug? Quote Link to comment Share on other sites More sharing options...
Anthony Scott 2 Posted July 16 Author Share Posted July 16 Same effect with a new plug & fresh fuel, Don but thanks anyway. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 16 Share Posted July 16 Blocked crankcase breather? Quote Link to comment Share on other sites More sharing options...
Andy Stephenson Posted July 16 Share Posted July 16 Valve clearances? Broken valve springs? Wrong timing? Quote Link to comment Share on other sites More sharing options...
RottenRow Posted July 16 Share Posted July 16 Are you able to run the engine on a test stand, in order to eliminate anything to do with the fuel tank and plumbing? Brian. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted July 16 Share Posted July 16 47 minutes ago, Martin Harris - Moderator said: Blocked crankcase breather? I heard from a very reliable source that the crankcase breather could be blocked off. I can see the point as running an inverted engine with the vent near the top is a bit pointless unless your are flying inverted the majority of the time! i suppose it lets the pressure inside the crankcase and outside to equalise, but is it really necessary? Perhaps the previous owner filled it with oil.... 🙂 Assume you are using the normal set up procedure, then IMO must the the plug...or the wrong prop (but you say its 16x8, but is it. IMO 16x8 is quite a big prop for a 150 and the 155 is a more powerful engine. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted July 16 Share Posted July 16 8 minutes ago, Andy Stephenson said: Valve clearances? Broken valve springs? Wrong timing? Didn't say if it was NIB from Laser or someone else, but if it was NIB then its early days for valve clearence or wrong timing...unless someone has picked it to bits and put it back wrong! Good point from RR...tank or plumbing...had a pinhole in a fuel line... only drew air when it was flat out. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted July 16 Share Posted July 16 If it isn't a valve spring, maybe it isn't properly run in, I only get around 8.600 rpm on the same prop on my Saito 150. Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 16 Share Posted July 16 4 hours ago, Anthony Scott 2 said: I bought my Laser 150 NIB in 2017, from 2019 it has been flown frequently in a 82" Seagull Spacewalker. I have never been able to get more than 7400 rpm, on Laser 5% & a Graupner 16*8 & using an OSF plug. Last weekend I had to abort a take off because of a loss of power on the 1st flight of the day. On running the engine in the pits the rpm audibly fell & the engine began hunting gently. I used a tacho on the next start & saw that the RPM was 7400 but that quickly by 1000 rpm & the engine was hot. Another start, with a richer mix saw the rpm fall from 6000 to 4300 with more hunting. When I took the valve cover off an inordinate quantity of clean oil flowed out. The engine has never suffered a crash, has excellent compression & the valve clearances are as specified. Ideas please. Tony A 150 of that era should do 8300-8500 on a 16x8 depending on the brand. Newer apc 16x8' run slow for some reason, around 8000. If its always run slow and always been in that model i recommend making sure the carb is actually opening all the way. Also, how hot is it? Check the throttle linkage, if that is opening fully take a video of the engine running and slap it up on here. fire it up, show the problem, retune it etc. Do it all on video but make sure the camera is out of the prop wash or we wont be able to hear anything useful. Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 16 Share Posted July 16 1 hour ago, Paul De Tourtoulon said: If it isn't a valve spring, maybe it isn't properly run in, I only get around 8.600 rpm on the same prop on my Saito 150. RPM will not change significantly with time or running in. When recently testing the rebuilt inlines they all ran the same +- about 100 revs. Some were new, others loads of hours. 1 Quote Link to comment Share on other sites More sharing options...
Anthony Scott 2 Posted July 16 Author Share Posted July 16 I think you are correct, Martin but I will investigate other suggestions. I am sure the throttle is opening fully. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted July 16 Share Posted July 16 16 minutes ago, Anthony Scott 2 said: I think you are correct, Martin but I will investigate other suggestions. I am sure the throttle is opening fully. What orientation is the engine? Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted July 17 Share Posted July 17 9 hours ago, Chris Walby said: What orientation is the engine? Now let's keep sex out of it ! 1 Quote Link to comment Share on other sites More sharing options...
Anthony Scott 2 Posted July 17 Author Share Posted July 17 Inverted. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted July 17 Share Posted July 17 (edited) Fuel tank has to be on the floor of the fuselage Ant Have carved up 3 models now to get the tank Low for inverted motor fuel feed. Edited July 17 by Denis Watkins Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted July 17 Share Posted July 17 1 hour ago, Denis Watkins said: Fuel tank has to be on the floor of the fuselage Ant Have carved up 3 models now to get the tank Low for inverted motor fuel feed. DW tank position accepted and engine mounted inverted I would expect the engine could still be set up to max RPM on the ground (although in flight it would be suboptimal) and then problems in flight would materialise. If the engine won't rev out its either Glow plug Throttle not wide open Tank vent restriction Fuel line restriction or hole allowing air in Exhaust restricted Someone has picked it to bits and screwed up the valve timing Valve spring, but IMO it would run My money is on its not engine, but one of the first 5 options. 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 17 Share Posted July 17 You could add camshaft or follower wear (particularly if case hardened) restricting valve opening/duration to the list. Cam wear wouldn’t show up on a valve clearance check as the base circle is unlikely to be affected. From the description in the OP, this seems to be a sudden onset in service problem so unlikely to be due to installation or interference. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted July 23 Share Posted July 23 On 17/07/2024 at 16:15, Martin Harris - Moderator said: You could add camshaft or follower wear (particularly if case hardened) restricting valve opening/duration to the list. Cam wear wouldn’t show up on a valve clearance check as the base circle is unlikely to be affected. From the description in the OP, this seems to be a sudden onset in service problem so unlikely to be due to installation or interference. ? But the original post said: I bought my Laser 150 NIB in 2017, from 2019 it has been flown frequently in a 82" Seagull Spacewalker. I have never been able to get more than 7400 rpm, on Laser 5% & a Graupner 16*8 & using an OSF plug. Last weekend I had to abort a take off because of a loss of power on the 1st flight of the day. On running the engine in the pits the rpm audibly fell & the engine began hunting gently. I used a tacho on the next start & saw that the RPM was 7400 but that quickly by 1000 rpm & the engine was hot. Another start, with a richer mix saw the rpm fall from 6000 to 4300 with more hunting. Martin, I can't see how you can make this statement "From the description in the OP, this seems to be a sudden onset in service problem so unlikely to be due to installation or interference." Ok the problem has got worse, but it gas never been right...install issue or someone else and messed around with the engine!. As for the engine being full of oil (as its being run inverted) just shows that the valve guides are in condition and there is lots of oil around the cams/valve gear. Once it over fills the timing chest it will go past the rings and be burnt....or somehow squeeze out of the vent line. I would gain confidence that there is plenty of oil in the engine rather than it being bone dry and if it needs emptying more frequently then just fly inverted for a bit. 🙂 I do like the little puff of smoke from the engine when doing a gentle roll Again "You could add camshaft or follower wear (particularly if case hardened) restricting valve opening/duration to the list. Cam wear wouldn’t show up on a valve clearance check as the base circle is unlikely to be affected." but Anthony's comment "When I took the valve cover off an inordinate quantity of clean oil flowed out" If the cam surface were would you not see metallic particles in the oil from the rocker area? IMO if you can only get 4300 rpm out of an engine because the cam/followers are breaking up it should sound like a bag of nails...and lots of metal in the oil!. My money is still on...nothing wrong with the engine, problem with : Glow plug Throttle not wide open Tank vent restriction Fuel line restriction or hole allowing air in Exhaust restricted Failing all else, engine out and onto the test stand and see what that yealds. If revs out then its the install, if not it can't be the install and must be the engine...simples. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted July 23 Share Posted July 23 The engine internals should be oiled but not "full" of oil as stated in OP . If too much oil is in the case this will be the cause of low rpm as engine just boggs down , Make sure that all the oilways that allow excess oil to be expelled through the breather nipple are clear . Being run inverted should not make any difference , Drain all excess oil and try again , This includes the rocker gear , this should be oiled but not have puddles of oil in the cover . Id also check valve timing as just one tooth out will cause a loss of performance . Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted July 23 Share Posted July 23 4 minutes ago, Engine Doctor said: The engine internals should be oiled but not "full" of oil as stated in OP . If too much oil is in the case this will be the cause of low rpm as engine just boggs down , Make sure that all the oilways that allow excess oil to be expelled through the breather nipple are clear . Being run inverted should not make any difference , Drain all excess oil and try again , This includes the rocker gear , this should be oiled but not have puddles of oil in the cover . Id also check valve timing as just one tooth out will cause a loss of performance . But the breather is in line with the crank and near the highest point with the engine inverted of course oil is going to accumulate in the rocker cover. More inverted fling I say and give it a chance for the oil to be expelled. Why pick it to bits...put it in the test stand with the cylinder head uppermost, start it tune it and give it a good rev against the prop until too hot to touch. I wasn't going to say this, but how did all the oil get in there? Slobbering too rich as the oil has to get past the rings to get in the crankcase? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 23 Share Posted July 23 I’m not trying to start an argument but simply suggesting additional possible causes. While the owner may have reported lower rpm than expected throughout the engine’s life, it has only just started this excessive power loss problem. He has stated that he bought the engine new in 2017 and it’s been run regularly. There may be a variety of explanations for its low “normal” rpm but this was not the subject of the original post. On other engines, the breather provides a drain outlet and a means for volume/crankcase pressure changes to encourage air/oil mist to flow over the cam and valve gear. This was the reason that Saito went to the considerable effort of providing an air pump on their earlier flat twins as there was no change in crankcase volume due to the common crank pin design. I still feel that based on the problem description, the first check should be that the breather is free. Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 23 Share Posted July 23 Just to cover off a few points. In the entire history of laser to date only one cam lobe ever wore out, so it is highly unlikely its a camshaft problem Cam timing is also going to be fine as a 2017 model would have been test run by me, and if it didnt achieve the rpm i expect on my test prop (8500 +- 200 on RAM 16x8) it would have been rejected and inspected. This obviously isnt true if someone has had it apart. All bets are off in that case. The rocker cover being full of oil is not a problem and is by design. The exhaust cam follower bush is modified to turn the cam follower into an oil pump and force oil into the rocker cover when the engine is upright. On its side and inverted it is very common for the whole thing to fill up. This is perfectly normal. Without a video of the engine running is virtually impossible to diagnose. The various noises it makes will be very telling. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 23 Share Posted July 23 20 minutes ago, Jon H said: The exhaust cam follower bush is modified to turn the cam follower into an oil pump and force oil into the rocker cover when the engine is upright. That is truly interesting information - was this in the original design or one of your developments? Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted July 23 Share Posted July 23 Yes that is a nice innovation, I would love to see a drawing and a few words to explain how it works, or is it just a hole in the cam follower ?. Quote Link to comment Share on other sites More sharing options...
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