On the infamous Virago starter, there are multiple problems and thus multiple fixes. Here are two I dealt with.
First fix, get the planetery ring gear welded to the part that holds it originally in a press fit. This v-shaped press fit did not hold long term and thus the ring gear would spin. The sun gear spins, the planet gears spin(attached to the "bendix") but the ring gear should not spin.
Second, the starter body is made up of two-ends with a middle cylinder all clamped together with two long bolts. The rear end cap bolts to the engine while the front cap just rides in an o-ring sealed port into the case. The whole starter will twist due to the torque being applied through the starter body all the way from the gear end to the other end where it's bolted to the case. The plate where the brushes are located has tabs that engage the body/end cap and keep them from rotating with respect to one another. These tabs will not necessarily hold against the torque and thus the starter body rotates resulting in binding, reducing the power available to actually spin the engine. Inspect these tabs and make them as prominent as possible by bending and filing good edges into them and the engagement points.
I also was never able to get the starter back on with the spring clamp on the end without taking off the side cover. I tried many times to get it back in through the starter hole but wasn't able to.
Those are some starter issues I remember from my ownership of an '82 XV750 back in the early '90s. I was never able to get the starter to function in top shape for more than a few thousand miles of small city commuting. Other than the starter, that bike was extremely reliable and because a push start makes the starter not entirely necessary, it never left me stranded. Something about the weight distribution/CG made it feel very stable even on soft ground or packed snow. One of these days, I'd like to get another for "good old days" reasons I suppose. Then I will likely realize how bad it really was...