straus19

I have an os 90 fs that only runs with the needle valve turned in tight. Even then it is still runing rich. Do you know what could cause this? I checked it with a needle from a diffrent os 90, still the same. Is there a replacement carb or a diffrent carb that will fit this engine? Thanks

Bax

My Feedback: (11)

It sounds like the needle seat in the carb body has been damaged and made a bit wider than it should be. The only cure is to replace both the carb body and the needle valve. Unfortunately, We'd not have parts for the old FS-90, and neither would O.S. in Japan. The engine has been out of production for 18 years and no longer receives support from O.S.

You can check the needle, and you'll likely see a polished ring around the pointy part. This indicates that it's been hitting the needle seat enough that damage has been done.

leoplanes

I had the same problem , probabilly the needle somehow was screwed too tight and damaged the small hole in wich it seals the fuel flow . I fixed that , taking a small punch , with a rounded end and slowly knocked the hole forcing it to reduce its enlarged diameter . This worked for me . Also is a good idea check your carburator seals , o rings etc . Its a fine engine , I have tree . Hope it works for you . Buying a new carburator is a good idea , but they are no longer available , and is difficult to find second hand replacement parts for that engine