Naw - the engine's seals are already waterproof, if they weren't they'd not be able to keep the fire & fuel in
ofc - that may not be tru w/alla these kits lol, but silicone isn't the way to fix that, partic not
smearin' it on the outside.
The only things that are water sensitive are the wiring & the carb's air intake/filter. The wiring is easy 'nuff, get some o'that shrink-wrap tubing for alla connections FTW and the air intake? Just make sure that it's faced so that if ya go thru a puddle it's not launching spray into it.
*shrug* that's it. You could
pull the magneto & clutch covers off and put a thin
layer of that goo on just the seal... but I've not bothered and my ride's been fine in all sortsa holocaust-style Maine weather