Paul james 8 Posted June 16, 2020 Share Posted June 16, 2020 Posted by Jon - Laser Engines on 16/06/2020 16:47:46: Posted by Paul james 8 on 16/06/2020 16:05:40: Spares for an old Laser..... I recently acquired another couple of older Laser engines, the smaller of the two is now stripped down fully for new bearings and a good clean (not in that order). I've clumsily broken one of the two piston rings so wonder if replacements are available. On the side of the engine lugs is the number 62 and three initials, the bore is 26.4mm and stroke 18 so by my reckoning 9.8533 cc or around .601 cu inch. If available I'd replace both while it is stripped down. Any clues where these might be found?? Sorry Paul. If its a 62 they were discontinued in 1992 and we no longer support them for spares or service. Your only hope is to either make a new one or there is a guy on ebay who offers replacements. A final option would be to forget it and run it with one. As long as its in the top slot it will run fine. Thanks Jon, it seems a bit of an oddball with a forward tilted plug but what I thought were the later purple Irvine type carb, I thought it would have a super tigre carb back that old?? It has the grub screws holding the carb and exhaust. Might well just stick the one ring in if I can't find one from the eBay guy. One question....why was it called a "62" when it actually measures up quite a bit below that? Link to comment Share on other sites More sharing options...
David Davis Posted June 16, 2020 Share Posted June 16, 2020 Gacvin Carter is your man for old Laser piston rings. This is for the 61, but he sells them for the 62. **LINK** Link to comment Share on other sites More sharing options...
Jon H Posted June 16, 2020 Author Share Posted June 16, 2020 Paul, it might have got a carb upgrade in the mid 90's when it was still supported. The stroke is 18.8mm so that is where the extra cc went Link to comment Share on other sites More sharing options...
Former Member Posted June 16, 2020 Share Posted June 16, 2020 [This posting has been removed] Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 16, 2020 Share Posted June 16, 2020 Yes, a Goldie with RRT2 box topped out in 1st somewhere north of 70 but I don't see too many singles topping the timesheets in racing these days. Torque is wonderful on a roadbike, but won't get you very far on track without revs and lots of them. I always found my Sprint ST gave a good compromise. Anyway - back to Jon's Lasers! Edited By Bob Cotsford on 16/06/2020 19:03:32 Link to comment Share on other sites More sharing options...
Former Member Posted June 16, 2020 Share Posted June 16, 2020 [This posting has been removed] Link to comment Share on other sites More sharing options...
Paul james 8 Posted June 16, 2020 Share Posted June 16, 2020 Posted by David Davis on 16/06/2020 17:55:12: Gacvin Carter is your man for old Laser piston rings. This is for the 61, but he sells them for the 62. **LINK** Thanks for that, have sent him a message 👍👍 Link to comment Share on other sites More sharing options...
bert baker Posted June 16, 2020 Share Posted June 16, 2020 My latest Kettle can boil in under 3 mins if you don't watch it Link to comment Share on other sites More sharing options...
Paul james 8 Posted June 16, 2020 Share Posted June 16, 2020 Posted by Jon - Laser Engines on 16/06/2020 18:05:14: Paul, it might have got a carb upgrade in the mid 90's when it was still supported. The stroke is 18.8mm so that is where the extra cc went Seems an oddball as I can't imagine measuring it out by 0.4mm on throw? Still the bore is going to be the important thing for a new ring. I've put it back together with the top one in for now, was going to fit a prop on it and noticed that the aluminium part of the prop driver was split right through! How anyone can have tightened it enough to split that I've no idea. I had a look in my box of old engines and hey presto found one that fitted straight on! It was from an old MDS 40 so I guess the engine is now a hybrid laser/MDS?? This is how the cams were when I took it apart, reckon they were right but can you have a quick look to confirm please 👍 Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 17, 2020 Share Posted June 17, 2020 Having pondered the correct assembly a few years ago when I rebuilt my 62, that picture reminds me that I've often wondered about the cam profiles on these engines and meant to ask Jon about them. In my experience, inlet cams are usually of higher lift, acceleration and duration than exhaust cams but unless both my memory and the assembly in this photo are both wrong, the inlet cam is the noticeably shorter duration one at the bottom of the picture. Do you have any idea why these profiles were chosen? Link to comment Share on other sites More sharing options...
Paul james 8 Posted June 17, 2020 Share Posted June 17, 2020 The 62 is now back together with new bearings and a single ring, I've heard from the ring manufacturer that there is no stock of the part I need at the moment but he will advise when more have been made. On to the next one which is much tidier inside, didn't need to change bearings or do a full strip down. It is marked 7S3 on the bearer, has the square fins, top mounted plug and a black irvine type carburettor. I'm guessing it is a 75 so will choose the prop accordingly. It was running a 14x7 when I bought the model. Link to comment Share on other sites More sharing options...
Jon H Posted June 17, 2020 Author Share Posted June 17, 2020 I think the cams are ok. Its hard to be exactly sure as its a bit dark in there but the positions look right. Martin, only the 70 has the pointy inlet cam and we did it because it went better in the days when it was a 45. I have assembled 70's with normal cams both sides and it makes very little difference these days. Link to comment Share on other sites More sharing options...
Robert Putley 1 Posted June 19, 2020 Share Posted June 19, 2020 Hello Jon, Reference my question re my Laser 80 quitting mid air, I see that your response to my question and my reply have mysteriously dissapeared from the post. So here is my answer again:- Prop. A Super 14x7 plastic, it is heavy. Plug, OS F. Quitting, intantaneous, running at around three quarters thottle. I have never put a tach to the motor. The last plug lasted about seven or eight flights, the previous one, a similar amount.. The motor has not had that may flights, possibly around fifty or sixty flights. The tank is pressurised, and the centre point of the tank sits around 8 mm below the carb. Thank you Link to comment Share on other sites More sharing options...
Ron Gray Posted June 19, 2020 Share Posted June 19, 2020 Robert, as a matter of interest, have you got a photo of the engine’s installation? Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted June 19, 2020 Share Posted June 19, 2020 Robert, you say the tank is pressurised, is that with exhaust pressure? Link to comment Share on other sites More sharing options...
Jon H Posted June 19, 2020 Author Share Posted June 19, 2020 Posted by Robert Putley 1 on 19/06/2020 02:58:53: Hello Jon, Reference my question re my Laser 80 quitting mid air, I see that your response to my question and my reply have mysteriously dissapeared from the post. So here is my answer again:- Prop. A Super 14x7 plastic, it is heavy. Plug, OS F. Quitting, intantaneous, running at around three quarters thottle. I have never put a tach to the motor. The last plug lasted about seven or eight flights, the previous one, a similar amount.. The motor has not had that may flights, possibly around fifty or sixty flights. The tank is pressurised, and the centre point of the tank sits around 8 mm below the carb. Thank you Why is the engine pressurised? It sounds like the tank position is ok so there is no need for it and we dont recommend it. Your dead plugs, when they come out of the engine is the coil all smashed up? If so its possible the first plug to die left its coil behind and its bouncing around on top of the piston. It sounds crazy but it can happen and if it whacks the new plug the coil gets mooshed. Beyond that, will it restart after stopping without refuelling and does it always go after the same amount of time in the air? Edited By Jon - Laser Engines on 19/06/2020 08:10:26 Link to comment Share on other sites More sharing options...
Gary Spicer 1 Posted June 24, 2020 Share Posted June 24, 2020 Just got through my first 4 pints of the new Low oil Laser fuel from Model Technics, very pleased with it used on Laser 70s and 180 much cleaner, less smokey slighly higher peak RPM (I think!). Thanks to Phil at Model Techinics ...an email then phone call and 4 gallons arrived next day at good price Link to comment Share on other sites More sharing options...
Jon H Posted June 24, 2020 Author Share Posted June 24, 2020 Good news Gary We are looking at it as the way forward for our glow range and will continue to review the oil content. I suspect we will end up at 5% eventually and perhaps lower still. We will see. Link to comment Share on other sites More sharing options...
Gary Spicer 1 Posted June 24, 2020 Share Posted June 24, 2020 (Dont Know how I doube posted..sorry) Yes and thanks to Phil for getting it out so quick! Jon, do you think it will be Ok to use on my 2002 180 the one you serviced last year with purple carb? Dont want to go back to the old mix, as it it so much cleaner. Link to comment Share on other sites More sharing options...
Bruce Collinson Posted June 24, 2020 Share Posted June 24, 2020 Jon, To save me going back miles whilst at work, is there a determinant point/date/age for Lasers to use the low oil fuel? Most of mine are under 3 yrs old but 2 100s and my 120 are nearer 10 yrs old. BTC Link to comment Share on other sites More sharing options...
Ron Gray Posted June 24, 2020 Share Posted June 24, 2020 Thanks for the heads up Gary, going to have to order some too I reckon! Edited By Ron Gray on 24/06/2020 13:16:09 Link to comment Share on other sites More sharing options...
Gary Spicer 1 Posted June 24, 2020 Share Posted June 24, 2020 I not sure what the minimum order is direct from Phil, 4 gallons was very good price inc shipping.. **LINK** Link to comment Share on other sites More sharing options...
Jon H Posted June 24, 2020 Author Share Posted June 24, 2020 Posted by Bruce Collinson on 24/06/2020 13:09:13: Jon, To save me going back miles whilst at work, is there a determinant point/date/age for Lasers to use the low oil fuel? Most of mine are under 3 yrs old but 2 100s and my 120 are nearer 10 yrs old. BTC In theory any engine after 1992 will be ok. The reason for this is that all engines made after 1992 have the same construction, materials, heat treatment etc. Engines made before 1992 are not constructed the same and will probably not tolerate the low oil fuel. There are some caveats though. If your engine has been run on castor for a long period and there is an accumulation on the big end of the rod its possible this will impede the flow of oil to the crank pin and cause a failure. This is true of any fuel, but the lower oil fuel is likely to be more vulnerable. Equally, if your engine has a crank pin that is a bit dodgy due to corrosion or scoring, this too is likely to be more vulnerable. Will these more vulnerable engines fail? No idea. There are too many variables to be sure. I suspect they will all be fine, but there will always be that one engine where it all comes together and it breaks. The risk of a problem is very low, and any engine in good condition should not suffer any ill effects. I test run all of the engines i repair on the low oil fuel and they all go like stink Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 24, 2020 Share Posted June 24, 2020 Re. that last word...does anyone else find the smell of the oil that is used by Model Technics rather objectionable? At the risk of stirring up some of the usual comments by some of the electrovangelists, it's often remarked upon when someone uses it at the field while our commonly used ML70 (I think) based Southern Modelcraft fuel gives a far more pleasant aroma. Is the use of this oil key to the lower content requirement or could I usefully add a gallon of methanol to a gallon of 10% nitro SM fuel which is 15% synthetic and ( whisper it quietly) 2% castor? Edited By Martin Harris on 24/06/2020 14:45:23 Link to comment Share on other sites More sharing options...
Chris Walby Posted June 24, 2020 Share Posted June 24, 2020 Martin, while the smell of the Laser 5 is not that unpleasant, its only for the duration of the warm up and I haven't noticed any in flight smell, the benefits of not using caster are clearly recommended by the manufacturer (Jon) and noticeable in use with low oil content fuel. What's the rational for using 1% castor (why not less or more?) or why bother? PS - I have 2 or 3 gallons of castor from the racings days if you fancy disposing of them (no warranty given). Link to comment Share on other sites More sharing options...
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