TT500 sprocket nut wanted desperately!

**Wired1** · 21st June 2008, 21:01

I'm in desperate need of the nut that holds the sprocket on the drive shaft for my 1980 TT500. I took it apart a couple of months ago and now all I can find is the tab washer - but no bloody nut. I have been through my "nut draw" trying every nut under the sun from other Yamaha engines but this must be some obscure size. PM me if you have a spare or if you know the thread size so i can go to blacks - must be metric. Otherwise I'll have to trailer the bike in to them!

**Wired1** · 22nd June 2008, 16:58

I turned the workshop upside down today and can't find the bastard - does anyone know what thread this is? It's about 18mm diameter with a 1.0mm pitch, must be metric surely. It's a right hand thread. My tapping chart doesn't mention 1.0 pitch, only 2.5 and 1.5 so it must be something more exotic.

**G-spot** · 28th June 2008, 19:29

Its a special nut that you will have to buy from your Yamaha dealer. Its not flat on one side.The days to short to explain the reason why its not flat

Good luck.

**Wired1** · 28th June 2008, 20:20

Yes I had to buy one from the Yamaha shop. It is just as you describe! Must be 18mm metric with a super fine 1.0 pitch. Put the new sprockets and chain on today so I'll take her out for a blast tomorrow if I can get it started!.

**G-spot** · 2nd July 2008, 18:13

Thats great, all the best with getting it started.

**Wired1** · 2nd July 2008, 18:58

Yep she runs sweet.

**gammaguy** · 2nd July 2008, 21:36

the manufacturers are past masters at making it hard to use the aftermarket;

Honda for example use bearings in HALF mm increments,and BMW use threads on their engines that are not known to any engineering firm i have ever dealt with forcing me to charge owners $26 PER BOLT for the flywheel(theres seven of them in that sub assembly alone)

Oh yeah,and the NSR 250 had LEFT HAND 7mm threads on some parts....

and we used to make fun of British bike owners with their whitworth threads.......