I don't think Yamaha has an alternative starter motor. I think it works all right if you keep it clean inside (the dust most be removed from the inside near the brushes; http://www.buf-online.kristianstad.se/~lars.sandstrom/starter.htm ) and the electrical fittings free from corrosion. A good battery is also nessesary of course.
If you want to change motor I think this can help you;
Posted.by David Wells on 18 February 2004 at 01:06:18:
In Reply.to: Re: starting problems XV 920 versus TR1 posted.by Speedy on 17 February 2004 at 13:44:16:
"I have Fitted a Suzuki GSXR1100 starter motor in place of the original, chosen because of its drive gear being identical,only longer. The later unit is fitted with four brushs and a roller bearing on the drive end. Finding GSXR1100 (L) starter motors should be very easy and cost effective (mine was $80.00 Australian second hand).A Ring will need to be manufactured to fit between starter housing and sungear/block housing, (I have exact dimensions if required).The end result is a powerfull,reliable starter that can be replaced easily if need be. "
You can also look here for more info; http://www3.sympatico.ca/g.boudreau/LarrysViragos.htm

It's in the 2003 discussion board. A reply to the last subject(29 dec 2003) ; "starting problems XV 920 versus TR1"

The XV920 has the short shaft starter engine(4X7-81800-60-00);
http://www.partsnmoreonline.com/PNMSite/XV%20Virago%2024-2009%20starter%20motor.htm
The TR1. has the long shaft starter engine(5A8-81800-10-00);
https://www.partsnmoreonline.com/PNMSite/XV%20Virago%2024-2008%20long%20shaft%20starter%20motor.htm
(The electrical engine is probably the same but the shaft that emerges from the planet gears are different.)
You can compare them at; http://www3.sympatico.ca/g.boudreau/LarrysViragos.htm
The upper right part of the picture is a TR1 (and Virago) starter and the lower left is XV920 and some other models.
So as far as I understand the Suzuki engine don't fit the TR1...

Hi,
i think it possibly can fit, with an adapter ring that David already mentioned. The upper right part of the drawing on Larrys Site shows the
TR1-Starter _with_ the planetary gear, and the shaft is the long one, because that silly freewheel must fit on it... But David writes: "A Ring will need to be manufactured to fit between starter housing and sungear/block housing", so i think the gsxr-starter comes without planetary gear, but its shaft will fit _into_ the planetary gear of the TR1. Here you can see how a gsxr starter looks like: http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&item=2469984162
Bye,
Georg