Jon H Posted November 1, 2022 Author Share Posted November 1, 2022 26 minutes ago, J D 8 said: My PAW diesels have air bleed carbs. My 249 does, but my 149 just has a go fast spout. I did have a carb for it but i lost it somewhere. Maybe i should try and make one... Link to comment Share on other sites More sharing options...
Andy J Posted November 9, 2022 Share Posted November 9, 2022 On 01/11/2022 at 19:09, Jon - Laser Engines said: John S - yea ok but how often do you loose a clunk really? I can think of only 1 time its happened to me in 30 years. Unless you take off vertically it wont matter anyway, at least not for a while. Must be having a run of bad luck with clunks as have had two come off this year. Could not work out why the engine kept stopping on the model until I checked the plumbing for air leaks only to find the clunk at the bottom of the tank. Second occasion was only found by chance when I had to remove the tank on a new model which has yet to be flown. May be worth checking all my models as there must be a third one lurking in the depths of the workshop. Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 9, 2022 Share Posted November 9, 2022 Silicone fuel tubing tends to swell and soften after long term immersion- do you make a habit of draining your (glow) fuel tanks? 1 Link to comment Share on other sites More sharing options...
aidan mcatamney Posted November 9, 2022 Share Posted November 9, 2022 I always make it a habit to drain my fuel tank at the end of a day's flying. Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 9, 2022 Share Posted November 9, 2022 I round off the ends so not to split the silicone tubing later on and a roughing up so that they don't slide off, I use a torch to see through the tank to make sure that the tubes are in place and shorten the clunk so that it wont foul the end of the tank, and with a felt tip mark the outlets. Link to comment Share on other sites More sharing options...
Ron Gray Posted November 9, 2022 Share Posted November 9, 2022 I now tend to add a piece of brass / aluminium tube in the clunk line to prevent it folding back on itself as I had that happen to me earlier this year! Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 10, 2022 Share Posted November 10, 2022 11 hours ago, Ron Gray said: I now tend to add a piece of brass / aluminium tube in the clunk line to prevent it folding back on itself as I had that happen to me earlier this year! I do this on really big tanks, but try to avoid 'nose over' landings.🥳 Link to comment Share on other sites More sharing options...
Ron Gray Posted November 10, 2022 Share Posted November 10, 2022 Mine happened as a result of carrying the fuse, nose down, to the pits, I think I must have bumped it along the way! Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted November 10, 2022 Share Posted November 10, 2022 12 minutes ago, Ron Gray said: Mine happened as a result of carrying the fuse, nose down, to the pits, I think I must have bumped it along the way! Maybe next time put your glass of beer down,,,😉 Link to comment Share on other sites More sharing options...
Ron Gray Posted November 10, 2022 Share Posted November 10, 2022 🍻 Link to comment Share on other sites More sharing options...
Don Fry Posted November 10, 2022 Share Posted November 10, 2022 I have an old Flair DVII, powered by an ancient Laser 75. It just had some minor repairs. The old prop, a 14x6 scimitar blade APC was fine for the job, but was tip damaged. None in the spares box, seem rare in France at the moment. I’ve bought a 14x6 Xoar prop, very pretty, to replace. Anyone any idea about how these two props compare? Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted November 10, 2022 Share Posted November 10, 2022 No, but never been unhappy using Xoar props Don. Link to comment Share on other sites More sharing options...
Don Fry Posted November 10, 2022 Share Posted November 10, 2022 Cheers John, I’m being a bit old maidish I suspect, it’s very nice but not as great granny made it mentality. Open the throttle and I find out. PS, it is old, you donated a Flair wheel for it a long time ago, blue now red, when I was one wheel on wagon, and no Flair wheels to be had. 1 Link to comment Share on other sites More sharing options...
Jon H Posted November 10, 2022 Author Share Posted November 10, 2022 with a wood prop i recommend you fit it, fly, and then let the engine cool down before giving it another go with the spanner. You will find its slightly loose and needs a tighten. Repeat this every flight until you find the prop has stabilised and is still tight after the engine has cooled. Normally takes 4 or 5 flights. 1 Link to comment Share on other sites More sharing options...
Engine Doctor Posted November 10, 2022 Share Posted November 10, 2022 Jon . Have you actually physically tried an inlet extention tube on a laser? The one I made some years ago for an OS made the engine run far better especially at low mid range with good torque up to nax piwer. Max rpm was down a tiny bit but nothing to worry about in the real world. It seems we have become fixated by statistics and squeezing every last rev from an engine. Fine on a race track or speed competition but it doesn't always translate to the real world applications. If its just max top end your after then the carb bolted onto the cyl head is fine. You quote motorcycles having very short inlet tracts but look back and you will find many old bikes especially those tuned for hill climb events etc had lengthened inlet tracts to increase torque especially in the mid range. Carb on the head equates to some of the fuel entering the chamber still in a liquid state . A longer inlet tract allows this wet mist to fully vaporise before it enters the cylinder and it burns better. If you haven't tried it don't knock it . I think I have already hold you about a work colleague who rebuilt his Triumph Boneville with extended carb tracts. Carbs were mounted on the frame with slightly flexible inlet tubes. No other Boneville around our scene could catch it . The only downside was that pulling away if the road was wet became a bit tricky as wheelspin was the norm and careful clutch control was needed. Would ib be worth trying a inlet extention and if it's works and helps tank position then sell it as a add on. I'm sure there would be a market. Link to comment Share on other sites More sharing options...
Andy J Posted November 10, 2022 Share Posted November 10, 2022 Looking at the picture of your tank Paul looks the same as the type of clunk I had come off this week. Think the issue is that there is simply not enough extension pipe on the clunk to engage securely with the fuel pipe inside the tank. Replaced mine with a sintered filter type which had a far longer interface pipe. Link to comment Share on other sites More sharing options...
Ron Gray Posted November 10, 2022 Share Posted November 10, 2022 Stainless steel tying wire? 1 Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted November 10, 2022 Share Posted November 10, 2022 Can't say I've ever suffered clunk problems, I buy the thick walled bluish fuel tube, dunno the make but it grips no problem, comes in various OD diameter to cater for small clunk use (bit floppier), maybe your choice of tubing at fault ? Link to comment Share on other sites More sharing options...
Jon H Posted November 10, 2022 Author Share Posted November 10, 2022 6 hours ago, Engine Doctor said: Jon . Have you actually physically tried an inlet extention tube on a laser? The one I made some years ago for an OS made the engine run far better especially at low mid range with good torque up to nax piwer. Max rpm was down a tiny bit but nothing to worry about in the real world. It seems we have become fixated by statistics and squeezing every last rev from an engine. Fine on a race track or speed competition but it doesn't always translate to the real world applications. If its just max top end your after then the carb bolted onto the cyl head is fine. You quote motorcycles having very short inlet tracts but look back and you will find many old bikes especially those tuned for hill climb events etc had lengthened inlet tracts to increase torque especially in the mid range. Carb on the head equates to some of the fuel entering the chamber still in a liquid state . A longer inlet tract allows this wet mist to fully vaporise before it enters the cylinder and it burns better. If you haven't tried it don't knock it . I think I have already hold you about a work colleague who rebuilt his Triumph Boneville with extended carb tracts. Carbs were mounted on the frame with slightly flexible inlet tubes. No other Boneville around our scene could catch it . The only downside was that pulling away if the road was wet became a bit tricky as wheelspin was the norm and careful clutch control was needed. Would ib be worth trying a inlet extention and if it's works and helps tank position then sell it as a add on. I'm sure there would be a market. I am not going into it all again ED. Its been done to death at this point Link to comment Share on other sites More sharing options...
Mike Mc Posted November 10, 2022 Share Posted November 10, 2022 (edited) Do the Laser 70 and 80 have the same mounting bolt pattern? Edited November 10, 2022 by Mike Mc Link to comment Share on other sites More sharing options...
Jon H Posted November 10, 2022 Author Share Posted November 10, 2022 (edited) 11 minutes ago, Mike Mc said: Do the Laser 70 and 80 have the same mounting bolt pattern? Nope. Wider crankcase on the 80. Dimension drawings for both are on the website though so you can check the fit in your model. Edited November 10, 2022 by Jon - Laser Engines Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted November 28, 2022 Share Posted November 28, 2022 OK very old Laser 75, but modified to use the black carb instead of the super tigre one, hadn't been used since I changed the main bearings. First flight it ran great and landed after 10mins and taxied back and I had to stop the engine with the throttle cut, so all good. 2nd flight it cut out in flight, back on the bench it seemed to be running OK, but on the third flight it cut when I dropped the throttle from full to 75%. Back on the bench and I noticed that the main needle was open about 4 turns and was quite insensitive. Checked the tank but that made no difference, BTW top of tank is level with the carb (upright installation) So I've had the carb off disassembled it and cleaned it, thinking there was an internal blockage, but there was nothing obvious I could see, as I've had to remove the engine to remove the carb is there anything else to check/change before I reassemble. Note it can't be the fuel as it's the same fuel as the first flight and used in my Laser 62 which just purrs through 20 min flights. Link to comment Share on other sites More sharing options...
Jon H Posted November 28, 2022 Author Share Posted November 28, 2022 Nope, sounds like classic carb blockage to me so i would do as you have done and give it another shot. Double check the valve springs to make sure one didnt break and that clearances are good. Beyond that i suspect dirt in the carb is the issue. Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted November 28, 2022 Share Posted November 28, 2022 Thanks, valve springs and clearances are all good, so I'll put it back in the model and give it another whirl. It's running on a MK 13 x 6 prop. 1 Link to comment Share on other sites More sharing options...
Mike Mc Posted November 28, 2022 Share Posted November 28, 2022 Jon, what's your thoughts on fuel tilters? I have them on all my airplanes to prevent problems like that. Link to comment Share on other sites More sharing options...
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