Incorrectly Assembled Model Engines

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1. About 1970 while in New Guinea Garth Bartlett approached me about his NEW Mills .75. The engine would run, but very POORLY. On checking I found the cylinder was the wrong way round ( 180 degrees out ) Garth had lost interest in this engine and asked if I would swap it for a NIB O.S. Pet 1.6 cc Glow. I still have the Mills .75
2. Brian Mason the president of the Doncaster Aero Club in Melbourne asked me to look at his son’s Enya 19. This was about 1977.He told me that they had been flying it in a C/L model, and after landing and refueling, the engine would not run correctly. It was taken to a model shop in Melbourne and checked, and was returned to Brian with the instructions that there was nothing wrong with the engine. The engine still would not run correctly. It was given to another model shop for checking. They fitted a new piston and liner, but the engine still would not run correctly. It would START but would not tune with the N/V. Brian asked me to have a look at this engine. I straight away realized that the cylinder liner was inserted the wrong way round. I fitted the original piston and liner back into the engine, and ran it for Brian.The story about flying the engine and then having problems, was obviously not correct as the engine had to be pulled apart to turn the cylinder liner.
3. Again at the DAC a junior member had two Enya 15 s fitted into C/L models. This was probably about 1985. He asked me to have a look at one of these engines, as it would START but would not put out any power, and would not tune up with the N/V. It was fitted into a Geoff Pentland 44” W/S Kawasaki Hein ( Tony ) On checking this engine after removing the muffler, it was obvious that the PISTON was in the wrong way round. The BAFFLE on the piston should be on the transfer side of the cylinder and it was on the EXHAUST side. The Cylinder Head had also been turned to fit the baffle.
4. Another junior ( Rohan Cleary ) at the DAC also had two Enya 15 s in models. One engine was difficult to START and would not tune. It had been used many times over the previous months I asked if the engine had been pulled apart, and I was assured that it had NOT been. On checking inside the exhaust port after removing the muffler, the piston baffle was obviously on the wrong side. The engine ran correctly after the piston and the cylinder head were fitted the correct way round.
5. A senior member of the DAC asked me to have a look at his O.S. Max 40 R/C which he had purchased S/H from another member. He told me that the engine would START but would not tune up, and was spitting a lot of fuel out of the carburetor. I suggested that he check the cylinder liner as it showed the typical symptoms of a cylinder liner the wrong way round. The following week he confirmed that the cylinder liner had been fitted the wrong way round by the previous owner.
6. About 2001 I was offered an O.S. Max S 35, very cheaply, by a hobby shop as I was told that it was probably only good for spare parts. I purchased the engine, as it was a C/L engine and had a muffler ( Very difficult to buy ) and a good N/V assembly. I had looked inside the exhaust before buying and noticed that the piston baffle was on the wrong side. I guessed that the engine had been pulled apart and re-assembled the wrong way round and probably had none or very little running.
7. Another friend John asked me to look at an O.S. Max 15 that he had purchased at a Sunday market. The engine looked NEW. The engine would START but would not tune up with the N/V. Another friend ( An engine collector ) looked at the engine and could not find anything wrong with it. As soon as I looked into the exhaust port I suggested that the cylinder liner was in the wrong way round. Normally when the piston is at the bottom of the stroke ( BDC ) the top of the piston is level with the bottom of the exhaust port. If you can see about 1.5 mm of the wall of the piston at BDC, you are obviously looking in through the TRANSFER port, which is slightly lower on the wall of the cylinder liner. After turning the cylinder liner round 180 degrees, the engine ran correctly.
8. Another friend loves his Merco engines. His Merco 35 broke a crankshaft in a C/L model. I had a new crankshaft made by a friend in Melbourne. The Merco was sent back to my friend overseas and fitted back into his C/L model. I visited my son in Dubai in the U.A.E. in 2003 and while there I was offered a fly of the C/L model with the Merco 35 and the new crankshaft. The engine had not been run since fitting the new shaft. The engine was difficult to START, and would not tune up with the N/V and ran very POORLY in the air. I suggested that the engine had been re-assembled with the cylinder the wrong way round, and I was found to be correct when the cylinder head was removed and the height of the exhaust and transfer ports checked. The engine ran well on the newly made crankshaft when the cylinder liner was fitted the correct way round.
9. About two years ago my friend Colin who I fly with at the Nambour Model Club in Queensland, was given an O.S. Max 15. It was very dirty. It probably had not been run, but was dirty after the owner tried to start it and left it on the shelf covered in oil. Colin pulled it apart and cleaned it and re-assembled it and loaned it to another member at Nambour, and it was put into a C/L combat model. The engine was very difficult to start, but this was put down to being a new engine. Eventually the engine started but would not tune with the N/V. The model was launched with a POORLY running engine and cut out on T/O. The engine was then re-started and still would not tune with the N/V, but this was put down to the engine being new and tight. The model was again launched but cut on T/O. I asked them to remove the muffler and let me look at the engine. The piston was about 1.5 mm above the bottom of the exhaust port when the piston was at BDC. I suggested that the cylinder liner was in the wrong way round. Colin immediately realized that he had not check the two ports ( Exhaust and Transfer ) when he had re-assembled the engine. When the cylinder head was removed and the two ports checked and it was confirmed that the cylinder was in the wrong way round, the cylinder was rotated to the correct position, the engine re-assembled, started very quickly and easily and peaked out when tuned with the N/V.
10. I purchased a Gordon Burford Taipan Tyro 1.9 cc Diesel at a Sunday market very cheaply. It looked new and I guessed that it had not been run. The cylinder had been fitted 90 degrees out so the internal transfer ports will not align and the engine will not run.
11. I purchased two engine on eBay about July 2005, a Taipan Tyro 1.9 cc Diesel and an Enya 15 111 Glow engine. The Taipan has the cylinder on 90 degrees out, and has every chance of running if fitted correctly.
12. The Enya 15 111 mentioned in No 11 above arrived with the piston fitted the wrong way round.
13. I purchased an Enya 19 V ( BB ) engine on eBay in England about July 2005. When it arrived I realized that the Cylinder had been put in the wrong way round. The engine looks very new and may not have been run, as someone had pulled the engine apart and re-assembled it the wrong way. I carry these three engines mentioned in No 11, No 12 and No 13 around in my model box and show them to my modeling friends, to help them to recognize this sort of problem.
14. The latest engine problem ( November 2005 ) came from a modeller in Sydney who had contacted me about a model plan for which he was searching . He mentioned by email that he had been given a C/L model and had acquired an O.S. Max 20 R/C engine, which fitted the model. The engine was running very POORLY and would not tune up with the N/V. I suggested that he check the piston baffle and the piston at BDC in relation to the exhaust port. He removed the cylinder head and confirmed that the piston was in the correct way BUT the cylinder was in the wrong way round as I had suggested. With the cylinder inserted correctly the engine ran at peak RPM We have sent him an O.S. 20 C/L Venturi and N/V and S/B ( OS Part No 2151 1000 ) which he should receive today as I am writing this. ( 23/11/2005 ).
15. The same modeler mentioned in No 14 above sent me an email on Friday 25 November 2005 with a photo of an Enya 15 that he was given at the same time as the O.S. Max 20. After reading about all the problem engines that I had found he decided to look at his Enya 15. Sure enough the piston was in the wrong way round. The baffle was on the exhaust side, and the baffle on the piston should be on the transfer side.
16. An Enya 15 111 was purchased from Canberra on eBay in January 2007. The engine appeared to be in excellent condition with glow plug and good N/V & S/B, but no muffler, and a little oil dried on the outside of the crankcase. The compression was possibly the best I have ever found on an Enya 15. The piston was in the wrong way round, the baffle on the piston was quite clearly on the exhaust side, where it should be on the transfer side inside the cylinder. The cylinder head is obviously also turned 180 degrees as there is a slot in the cylinder head to accommodate the baffle on the top of the piston. Engines that have been incorrectly assembled as is this Enya 15 111, will start, with difficulty, but will not tune up with the N/V and will not reach peak RPM.
17. I spent about twenty years helping out at the Carey Grammar School Model Club. One of the members offered to sell the teacher, who supervised the Club, two OS Max 111 15 s, for use by the club to teach the other members to fly C/L while they were constructing their own models. The teacher mounted one of the engines into a Dick Steele Stick Trainer. He then had difficulty starting the engine, and when it did start, it would not tune up correctly. I removed the muffler and after looking into the exhaust port, told the teacher that the engine had been incorrectly re-assembled and that the cylinder was in the wrong way round. He turned the cylinder round 180 degrees, and the engine ran correctly.
18. The second of the two OS Max 111 15 s was then mounted in the same model, and again the engine was hard to start, and when it did start, would not tune up to a full two stroke tune. Again we checked the cylinder, and this second engine had also been re-assembled, with the cylinder porting 180 degrees out. We then realized why the Club member ( a Junior !!! ) wanted to get rid of these two engines
    

I have fixed these problem engines over the last 35 years. An article appeared in the American magazine Model Aviation in I think March 1989 by Tom Francher, and he explains that he helped a friend who had purchased a second hand Super Tigre G 21/46 C/L engine, and the engine was hard to start, and would not tune up correctly and was running with a very hot crankcase. There was a drawing with the article showing the different heights of the exhaust port and the transfer port on a cylinder liner. The EXHAUST PORT is the HIGH one Tom also explained the hot crankcase, as the exhaust gasses are going down into the crankcase as the exhaust port is opening first when the cylinder is in the wrong way round, and this is allowing the exhaust gasses to go into the crankcase and stops the correct flow of new fuel into the cylinder. I have written this up as over many years I have explained this problem to many friends and felt it was about time that I listed all the various engines that I had found with incorrectly assembled parts .

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