its not too much ,,,,,,,,,,,about 2 years before i convert a briggs and staton engine into self start and then auto start,,,,,,,,,,,it was recoil kick start ,,,,,,,,i found some junk parts of briggs and staton engine but that engine was of bigger cc,,,,,,,,,,,,,i cant fit its fly wheel on my engine,,,,,,,,,i noticed that the fly wheel gear can be fitted on my fly wheel,,,,,,,,,,,,,and also the starter motor,,,,,,,,,,,,,,,there was no magnets inside my engine fly wheel so i use a 12V transformer runned by generator 220V output to charge the battery ,,,,,,,,,,,,,all thats cost me more than 5K,,,,,,,,,,,