Hello,
Parts for F engined Lawn-Boys are getting harder (and more expensive) to come by.
I'd check the compression (minimum 90 PSI) to see if it's worth the effort to invest more time and money in.
2 cycle engines are extremely simple in design, and if it's got decent compression, it should run good. If it doesn't it's usually a carb issue, assuming it's got good spark.
Regards
Jeff