this may help with finding out what a part should be and the diffrences.
the model number is the starting model and may fit later models but does not note this.

info posted by amakarovnik in another post:

It is helpful to understand Yamaha's parts numbering system when you're looking for parts. Yamaha part numbers can be found on many sites, among them http://www.yamaha-motor.com/sport/parts/home.aspx.

In the case of XV920 rings, the part number is 5H1-11610-00-00.

5H1 designates the first Yamaha model using this part.

11610 designates piston rings

The first "00" means the original part for this model. If the part was subsequently revised, these 2 digits would be "10"; next revision "20", etc. In the case of piston rings, "00" means standard size, "10" means 1st oversize, "20" means second oversize.

The second "00" refers to a color code. In the case of piston rings, color doesn't matter. In the case of fenders or sidecovers, the part numbers for different years of the same model may differ only by the color code - the last 2 digits.

With a little research, you too can determine that the same connecting rod (5A8-11650-00-00), wrist pin (5A8-11633-00-00), intake valve (2J2-12111-01-00), and exhaust valve (5A8-12121-00-0) are used in XV920s through XV1100s, but not XVS1100s. The same crank bearings (5G5-11656-00-00) are used in the XV700s through the XVS1100s. The same piston rings are used in XV1100s and XVS1100s (1TA-11610-00-00), but different rings in the XV1000 (5A8-11610-00-00).

And now, a real secret: the system for hardware.

The first set of digits identifies what kind of hardware:
98501 = panhead screw
91311 = allen head screw
92990 = lockwasher
etc.

The next set of digits give the dimensions - 05010 is 5mm diameter, 10mm in length.

For example, want to replace the crankcase cover screws with stainless steel screws? You need 3 6x20mm (91311-06020), 9 6x25 (91311-06025), 8 6x30 (91311-06030) and 4 6x40mm (91311-06040). And don't forget to use antiseize.

With these codes, you can replace fasteners not covered in the usual kits of chrome/stainless fasteners.

Don't forget that some fasteners are high tensile strength, so you shouldn't substitute a weaker fastener that's the same dimensionally.

So, correct me if I'm wrong. The first 3 numbers/letters (model code) make no diffrence, when looking for interchangable parts. As long as the following numbers match?

not necessarily. part may have same basic code, but have differences between models. some '81-'83 model parts don't interchange with '84-on or other models. (XJ,XS,etc)

If all the "numbers" match, it will work. for instance (1100)-1TE use some (700)-4X7 parts.

as geo suggests, do a part search at http://www.starmotorcycles.com/star/myyamaha/prompt/L3N0YXIvcGFydHMvaG9tZS5hc3B4/Parts%20Catalog/starthere.aspx

I'm looking to find out what rotors(flywheel) will work on my 85 xv1000. I have used the parts fiche and determined that 84-85 xv1000 are pt.#42h-81450-20-00. These are the only two that are exact match. When looking at all models from 84 xv700 thru 90 xv1100 all numbers accept the first three are the same.( Example 85 xv700 is 20x-81450-20-00 and 87 xv700 is 1rm-81450-20-00) I've been told most of these will work on my bike. How do I know witch ones for sure?

I would be real surprised if any '85 - on didn't fit, but that is just my guess.
Sorry I'm not more help.