You’re spot on it’s a low time engine. Cast iron pistons have a way of telling you they’re not happy when breaking in. They typically sag and fall off the power when overheating. Kind of like what you had there David. They also need a longer warm up time compared to ABCs and the cold weather there would have increased the warm up even more. A but more richening of the low speed along with some 4-stroking of the high speed for a couple more tanks will do it wonders. 12400 rpms is very healthy for a 9x6 prop on FAI fuel! Imagine it running on 15%! Fantastic run David of a classic 25 FSR iron piston.
thats a great runner. it will idle low for a 2 stroke, and it will really rev, like its little brother, the 21 fsr. the 21 fsr was designed to rev as high as 31,000 rpm.
Very good running engine! I have faced some problems in starting my engines at low temperatures in the past (so I warmed the housing up to 30 degrees Celsius and in most cases the engines started after that). The lighter fuel really works pretty well. I don't own a 25 FSR but a 21 FSR-C used in RC cars and I got both an extreme and small cooling head for this engine so it could be used for an RC plane as well. I really like the OS engines a lot, big or small. Thanks for sharing.
Looks like you found a very nice engine. If you can find a sig Kadet LT 25 it is an easy build and a very relaxing airplane to fly. This engine would fit an airplane like that very nicely and give more smiles per hour than miles per hour.
Thank you Dave for the video. Strangly enought, but i bought two 25FSR this week, i will run them similar what you do. But the running condition in Sweden is not so good for the moment. So i might just look at the video and wait for the spring. Greetings from Sweden
You’re spot on it’s a low time engine. Cast iron pistons have a way of telling you they’re not happy when breaking in. They typically sag and fall off the power when overheating. Kind of like what you had there David. They also need a longer warm up time compared to ABCs and the cold weather there would have increased the warm up even more.
A but more richening of the low speed along with some 4-stroking of the high speed for a couple more tanks will do it wonders.
12400 rpms is very healthy for a 9x6 prop on FAI fuel! Imagine it running on 15%!
Fantastic run David of a classic 25 FSR iron piston.
thats a great runner. it will idle low for a 2 stroke, and it will really rev, like its little brother, the 21 fsr. the 21 fsr was designed to rev as high as 31,000 rpm.
Very good running engine! I have faced some problems in starting my engines at low temperatures in the past (so I warmed the housing up to 30 degrees Celsius and in most cases the engines started after that). The lighter fuel really works pretty well. I don't own a 25 FSR but a 21 FSR-C used in RC cars and I got both an extreme and small cooling head for this engine so it could be used for an RC plane as well. I really like the OS engines a lot, big or small. Thanks for sharing.
David, thanks for the video.
Looks like you found a very nice engine. If you can find a sig Kadet LT 25 it is an easy build and a very relaxing airplane to fly. This engine would fit an airplane like that very nicely and give more smiles per hour than miles per hour.
Ran the 25 fsr in the late 80s early nineties great engine.
Certainly a very, very impressive little engine, great run!
Thank you Dave for the video. Strangly enought, but i bought two 25FSR this week, i will run them similar what you do. But the running condition in Sweden is not so good for the moment. So i might just look at the video and wait for the spring. Greetings from Sweden
I m always impressed with the performance of the OS 25 but I hate that 'mosquito syndrome'.... high pitch sound of little engines.
I have a few of these and have one on a Sig Kobra with the one piece header pipe on it. plane was built around 82 and still flying