Get yourself a 3/8" male to 1/4" hose barbed fitting like you use for air hose and slip a short piece of hose with a hose clamp on the fitting end and on the other end of the hose slip a Trojan (or balloon) over it and cinch it tight.
Plug it into the #1 spark plug hole (surprise it screws right in!)
Turn motor over by hand and wait for it to grow big.... when it starts to get smaller you went to far.
Or you can use a piece of wire and 'feel' for it...
