front rotor

[pratstyle]

i have a 2 piece front rotor i had polished went to put it on build and the caliper would not fit with it ? any ideas why.. the bike is an 80. thanks

 

[scabber]

WRONG ROTOR. If it is the right diameter and the offset is wrong you need to add spacers between the caliper and fork leg.

 

[XSLeo]

The two piece rotors were used with the two piston calipers, from 72 to 76. In 77 they went to a one piece rotor. As Scabber said the offset is different, the early have more off set to fit the two piston caliper. The later have less offset to use with a single piston caliper.
I don't think adding a spacer behind the rotor will work, wrong way to move the rotor. Adding a spacer between the caliper and fork won't either, moves the caliper too close to the wheel.
You need to get an 77 up one piece rotor.
Leo

 

[pratstyle]

i have a 1 piece on now .. if i got the older caliper would it work?. we tried a couple mounting options including a spacer on the axle.. non worked..

 

[5twins]

No, the older caliper has a different mounting bolt spacing and won't match your newer forks.

 

[XSLeo]

The easiest way to use that rotor would be to swap your complete front end, forks and trees for the earlier 34 mm forks and tree. This would need adapters built to use the dash and gauges you now have or swap the dash and gauges too.
But why back up to an older fork?
Just sell that rotor on Ebay. If you want a two piece get one off a more modern bike. On here some where is a list of more modern bikes that use a rotor that bolts right on your wheel. You may need to add a spacer to line things up.
Leo

 

[pratstyle]

THANK YOU .. looks like ill list and sell it since i did polish it already . i wont be going the route of switching everything .. i have shaved forks except for the brake ears.. plus the stock actually looks better..