A little more clarification on Yamaha Part numbers. The first three digits, in this case you have 4NK and 4XY are model codes. This indicates the first Yamaha model that part was used on. These three digits are also in the Primary ID and VIN of the first applicable model. The second five digits is the part type. YOU are missing a digit in your post, but as a general rule all front brake master cylinders will have the same 5 digit part code. The last two sets typically end in 00-00 or 10-00. The first set of two are typicaly supercedes, say from 00 on the original part to 10. If there is a finish difference , that is usually in the last two digits, and are typically letters.
If you look up part numbers for the Royal Star clutch ( I used a 2006 RSTD), the majority of them start with 26H. For instance the clutch basket (Primary Driven Gear Comp) is 26H-16150-10-00. 26H is the model code for the 1983 Venture. If you have a 1983 Venture you also will see that 26H is digits 4 5 and 6 of your VIN. Typically superceded parts are, improved and superceded parts with the same 3 digit model code are interchangeable. Another example. Fuel filters. 6K8-24560-10-00 and 1FK-24560-10-00. 24560 tells you its a fuel filter since all fuel filters are 24560. 6K8 is a fuel filter from a Yamaha Waverunner, 1FK is a Royal Star fuel filter, and no they don't interchange.
2009 Venture Frt Master Cylinder 4XY-W2587-10-00
2007 Royal Star (XVZ13AJ) Frt Master Cylinder 4NK-W2587-02-00 ( and from Yamahas website this number superceded from 00-00)
If a part number has a different model code, that means the part is unique to that model. If I had to guess, the difference in the venture master cylinder and the one for your RoyaL star, is the mounting angle to the handle bar. Different handlebars and handlebar pull back, angle etc would make this part of the casting unique, and thus model specific. If it takes the same rebuild kit , than the bore diameter and stroke is the same. IT will probaly physcally fit (assuming the handle bar diameter is the same), but the installed angle may be wrong and may affect braking, fluid angle in the reservoir,etc.
Unless you Brake master cylinder has physically broken castings or severe pitting on the bore, it should be servicable. I have seen very few that couldn't be cleaned up, honed and reused.
Last edited by RSTDdog; 04-16-2012 at 01:45 PM.
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