550 Seca owners need your help please

Chacal and I are trying to unravel some apparent discrepancies in the 550 Seca rear sprockets, between what the specs called for and what was actually produced/sold.

If you have reason to believe your rear sprocket MIGHT be original please post answers to the following if you would:

Model year/manuf date of your bike (ie; 1981 manuf 12/80

What COLOR (silver or black) is your rear sprocket;

And how many teeth does it have. For the last one, please count, do not go by the book (even factory book.)

Thanks in advance---Fitz

 

Mine has 45 teeth. Counted twice and divided by two LOL. It is stamped 45 and made of steel. Raw steel color. Not sure if it is orginal. I'm not the orginal owner, I got the bike after the chain broke and broke the starter off the block. I can only assume the drive train has been replaced. I can PM you the frame number if you need it. I hope this helps.

 

I recently had my rear wheel off in order to replace my (very badly) worn brake shoes and remembered this thread. I counted the teeth on the rear sprocket and came up with 44. The rear sprocket is also black, not silver/bare metal. Hope that helps a little.

The chain was extremely tight, even with the rear wheel completely loose and I had to pull the front sprocket in order to get the chain off. Counted them up, and the front sprocket has 14 teeth on that one.

Considering the # of teeth on my sprockets and how tightly the chain fits (and a number of other things on the bike), I have reason to believe the sprockets and chain were all replaced by a PO at some point. Either to repair damage, or likely to try to do something like change the ratios in order to improve torque, lower RPMs, etc.

 

You're right, that's not a factory configuration. I haven't found an ORIGINAL black sprocketed-bike yet, although I have both a 45T and a 46T OEM Yamaha (NOS replacement part) in black. From everything I've found, thay ALL shipped with silver 45T sprockets. The black sprockets came from the parts room, and are listed as such in the fiche.

I also haven't found anyone whose '81 was factory-equipped with a 46T even though Yamaha swears they were.

 

Not sure about the teeth count, but my 1982 550 RJ has the raw metal rear sprocket. I have no reason to believe it isn't original.

On a side note, I've never had problems getting the chain off to remove the wheel unlike Kyrrin.