Starter not Engaging

My Mark 3 starter is not engaging every time I try the electric start. Seems like 50% of the time. up 'til last week it was engaging 100% of the time.

The starter motor is OK, it just makes the spinning sound.

I installed a new sprag bearing over the winter. Other than failure of that pretty expensive piece, what other reasons might lie behind the intermitant starter?

Pull primary cover, it has to be something wrong inside if the starter is spinning...right? Everything is meshed gears except for the sprag clutch, me thinks.

Mike

The two bearing surfaces on either side of the sprag, namely the drive sprocket and crank gear, wear along with the sprag. These two pieces have to be checked, and, unfortunately, replaced if out of spec. If the sprocket is spinning, then the sprag rollers have flipped over, and you very likely have at least one of the mating parts out of spec. When I rebuilt my Mk3, I sent the assembly, i.e., the sprag, crank gear, and sprocket to Fred at OB (and the anti-backfire piece as well) for a tolerance check. Fred replaced the sprag and one of the two mating parts, and returned the new and good parts to me within a few days. You're looking at several hundred bucks, but, on the positive side, my starter has worked flawlessly for the past two years with the new parts.