OS @81 adjustment - Getting there, but not 100%
10-15-2024, 04:24 AM
#1
OS @81 adjustment - Getting there, but not 100%
Hi all,
Will try to do this short... I few years ago, I acquired an used OS @81. It needed a valve adjustment before first test run. Good compression felt after adjustment. Carb was dismantled and cleaned out just to be sure there was no debris in there. 13x8 prop in a .40 GP piper cub for first flight. Fuel --> 15% nitro, 20% oil. New OS F-plug fitted. Engine started nicely, and needle valve set a few clicks on the rich side after reaching max RPM with the tachometer, then started to adjust the low speed needle. Despite a lot of adjustment, I was not able to get the low to high speed transition right. Seemed to go rich at idle all the time, unless how much I turned the low speed needle in until the point where it would stop when opening the throttle. At the end, I suspected that the glow plug was not working properly. With only an OS no.8 plug available, I tried that one. Oh yes! that made a whole difference!! The engine then had a much better transition from idle to full throttle, but not perfect. The engine have had a handful of flights after that and working OK. The engine was this spring placed in a GP super sportster .60 and I fitted new bearings in the same move as the old ones showed some sign of corrosion. Engine behaves the same in this plane but still a few niggles that I am not to happy about:
1. At the initial start for the day, I have to unscrew the needle valve about 2 turn to make it able to start, then let it run for about 30 secs before turning it back in to the optimum high speed setting. Why??
2. It still seems to run a bit rich at idle, and starts stuttering and eventually stops after idling for a period. Turning the low speed needle in further will only make it stop when opening the throttle. I can basically not understand this. I have ordered an OS no.10 glow plug (cold) to try out based on the experience above.
3. What prop is recommended? the 13x8 Master Airscrews seems a bit heavy for this model. Have ordered a 13x6 and 13x7 to try out.
I have flown with different OS and Saito engines for 2 decades and always get them run smooth and nice, but this one is a *******! I have to admit that I am not to fond of the internal crankcase breather. Just wondering if this one plays a role for the set-up? Also makes it hard to inject some after-run oil to the crankcase
So, I hope any of you have some helpful advice
Will try to do this short... I few years ago, I acquired an used OS @81. It needed a valve adjustment before first test run. Good compression felt after adjustment. Carb was dismantled and cleaned out just to be sure there was no debris in there. 13x8 prop in a .40 GP piper cub for first flight. Fuel --> 15% nitro, 20% oil. New OS F-plug fitted. Engine started nicely, and needle valve set a few clicks on the rich side after reaching max RPM with the tachometer, then started to adjust the low speed needle. Despite a lot of adjustment, I was not able to get the low to high speed transition right. Seemed to go rich at idle all the time, unless how much I turned the low speed needle in until the point where it would stop when opening the throttle. At the end, I suspected that the glow plug was not working properly. With only an OS no.8 plug available, I tried that one. Oh yes! that made a whole difference!! The engine then had a much better transition from idle to full throttle, but not perfect. The engine have had a handful of flights after that and working OK. The engine was this spring placed in a GP super sportster .60 and I fitted new bearings in the same move as the old ones showed some sign of corrosion. Engine behaves the same in this plane but still a few niggles that I am not to happy about:
1. At the initial start for the day, I have to unscrew the needle valve about 2 turn to make it able to start, then let it run for about 30 secs before turning it back in to the optimum high speed setting. Why??
2. It still seems to run a bit rich at idle, and starts stuttering and eventually stops after idling for a period. Turning the low speed needle in further will only make it stop when opening the throttle. I can basically not understand this. I have ordered an OS no.10 glow plug (cold) to try out based on the experience above.
3. What prop is recommended? the 13x8 Master Airscrews seems a bit heavy for this model. Have ordered a 13x6 and 13x7 to try out.
I have flown with different OS and Saito engines for 2 decades and always get them run smooth and nice, but this one is a *******! I have to admit that I am not to fond of the internal crankcase breather. Just wondering if this one plays a role for the set-up? Also makes it hard to inject some after-run oil to the crankcase
So, I hope any of you have some helpful advice
10-15-2024, 06:17 AM
#2
Senior Member
No experience here but here is a review. I know a trick that works with Saitos, set the LS needle with the HS needle at full peak, that may do the trick. The needles effect each a certain amount.
https://sceptreflight.com/Model%20En...81%20FS-a.html
https://sceptreflight.com/Model%20En...81%20FS-a.html
