C@sutton

I wonder if someone can help me, i have just bought a Yamaha DT175, its a 1978 engine. The bike had been stripped for offroad/green lane use, so no oil pump. The previous owner told me that he mixed the ratio at 40:1. I run it on Castrol TTS at the moment, does anyone know if this ratio is correct? Someone had spent a lot of time on it and done work to it on both engine and frame, the reason im asking is because im not familiar with two strokes & it may sound stupid but the pistons sound dry when its running. Is this normal? I have not used the bike properly yet, I bought it in the winter and have been working on it myself and obviously concerned about the mixture ratio and how it sounds. The gearbox oil is clean, and everything seems to work ok but have not really tested it anywhere at the moment. Just want to make sure everythings ok. Any help appreciated. Thanks.