Maybe clean and drop of oil on that starter bendix gear so it moves up and down freely. I usually check and oil mine about once a year to be sure. No way you have battery hooked up backwards?...that'll make starter turn the wrong way on some motors. Good Luck!
Weak battery, dirty contacts, pitted starter solenoid. Not getting enough current to starter to spin it fast enough to engage....or bendix needs oiling as stated by Mr. Graham.
I hope the OP figured it out. Do not want to Hijack their But a Question: where is the Bendix on the straight shaft starters? Is it in the Flywheel Housing>?
