Can anyone help with a starter problem that is driving me crazy? I have a 1984 982cc TR1. When I press the starter button the starter motor spins but the engine only turns over slowly and then stops. The starter motor continues to turn I can hear it. It is as if something is slipping between the starter motor and the engine. If I remove the spark plugs the engine turns over OK. I have removed the starter motor and drive gears. All the splines and gear teeth are good. The starter motor clutch seems good. The clutch rotates easily in one direction on the starter motor shaft and locks solid in the other direction. I have cleaned out the carbon dust from the end of the motor. I had the starter motor field windings and bushes replaced 200 miles ago. Does anyone know what the problem could be? Please !!!

Hello Lars. You are a genius.
You were right first time. I drilled a hole through the starter motor body into the planetary ring and installed a self tapping screw. It was a five minute job. The starter motor now works better than it has ever done before, I have obviously had this problem developing for some time.
I had aleady looked at the planetary ring but had assumed it was meant to rotate. There is no locating pin to secure the ring in place. Is the ring normally a 'push fit' when new?
Once again, thank you. Kevin.

I had this problem too, and before I found solutions from these web postings I engineered a slightly other way.  I first tried to use the additional shim idea but was not able to ever find one, but if found or made I think the shim is the safest and best solution.
The planetary ring gear is a problem because it acts as a clutch when excessive back pressure is on the engine making the starter slip to prevent possible damage to the engine.  However, it slips to easy causing much frustration in starting the engine.
Since the planetary gear is a fairly soft metal, I drilled a hole 1.5mm diameter in the casing and halfway into the planetary gear.  Then put a shear pin (about 10mm long and 1.5mm diameter) then put a securing band clamp around the outside of the starter to hold the pin in place.  This pin should break with excessive resistance on the engine, not a guarantee to slip when needed but more likely to prevent engine damage then locking it with a screw.  The Specific damage I’m referring to is if an engine cylinder hydraulics from fuel leaking thru the carburetor into a cylinder when not in use, then starting. With the solid liquid in the cylinder could cause head gasket to blow, damage rings or piston, etc. Virago known problems causing fuel to leak is the O ring that can leak in the carburetor at the inlet set.  Also the petcock diaphragm leaking, sucking fuel thru the vacuum line.  I’m not responsible for any damage to your bike. Follow these repairs at your own risk!!!
Good luck