starter

Sounds like the spraq clutch failed. 

Call Rainbow Aviation in Corning they should be able to assist further.

(530) 567-5141

https://rainbowaviation.com

They are not in Corning any more. They still answer that phone number but they are in Missouri . I think you are right though so im looking for some one to do or help me do the spraq clutch. 

The root cause of spraq clutch failure is older ignition modules that do not delay spark until after TDC on starting, causing kickback with starter motor engaged thereby damaging the spraq clutch. 

Before going down the very expensive Sprag clutch route (likely if you've been using a weak starter for years like ours), may be worth checking you have a decent battery (Gel/ AGM type) with lots of CCA (Cold Cranking Amps), and decent thick cable to the starter, and clean earth terminals for the return from engine to chassis. No point in having a good HD starter if you cant feed it enough amps when asked for.

We had literal years of issues, initially replaced sprag clutch (Original to number 2), replaced ignition modules (ouch!), replaced battery, fine tuning carbs, replacing ignition cables, but the best hit was/is the Heavy Duty Starter motor.  Quicker the crank turns the more electrical energy is produced to feed the caps in the starter module (you need to get above a threshold RPM otherwise you wasting your time).  That and we replaced the starter circuit (choke) section of the Bing Carbs.  Now starts in all conditions from stubborn refusal.  Unfortunately we did have to replace the Sprag clutch again (number 2 to number 3) as the the continual use with the previous starter had completely worn it out again.

We also use the 'flywheel' starting technique.  Instead of switching on the mags , then cranking with choke.  We start cranking with choke (only for about 2 to 3 secs) then feed in the mags, in most cases this (for us) leads to a very smooth start with seldom any kick back).

I'd still contact them, they would be a great source to recommend a qualified mechanic.