The victa series 70 was a very good running engine, shame the imperial was rubbish. Even though official power fidguers were never published I would estimate from experience the 125cc in stock form was 4.5hp or thereabout, a lot more than required on a 14" and 16" reel mower.
The engines in the imperials are great, the only people who have gripes with them either lack maintinance or have a problem with the company in general, unfortunately the lack of a slippable clutch and very fast drive ratio made it a horrible machine to use. I have 2 of them, they have been in disuse since I aquired four scott bonnar 45's
