front end swap

[yamimoto]

I read a lot but don't post often and I can't find an answer. Help.
Will a 1978 Special front end swap directly onto a 1975 front end?
Thanks.

I should have been more specific. I want to change the whole front end including triple tree etc.

 

[5twins]

Yes, if you use the '78 triple trees. The '78 uses 35mm tubes, the '75 uses 34mm tubes, so appropriately sized trees are needed. Also be aware that the '75 brake caliper won't mount up to the '78 forks, the mounting hole spacing is different. And one more thing - if you use the '78 caliper, it won't match up to the '75 disc (different offset). So, to do the swap as a simple "bolt-on", you'll want the '78 forks, trees, disc, and caliper.

The MC is another item that may need changing. The '75 unit is sized differently because it pushes 2 pistons. That may or may not work so well pushing just one piston on the later caliper. I guess the best advise would be to try it and see.

 

[XSLeo]

I put a 79-82, parts from all them years, front end on my 75. You need all the parts 5twins mentioned.
The M/C from the 75 will work but it is a bit big. It's a 16 mm bore, a 14 mm bore will work better. As in 77 up. A 11 to 12 mm bore will work best with just one 77 up caliper and disc. The 14mm works great with a dual disc set up.
Leo

 

[yamimoto]

As always you guys have great answers. Thank you. The plan is to use the complete front end from the 78 and install a dual disc set up. What are your thoughts on using the 19" mags on front, and rear with disc and the Omar kit etc? I'm planning on using the 78 swing arm for the disc set up. I'm not building a tracker, more like a slightly modified stock 75. Hopefully a complete restoration. Engine is in the shop now. Planning on Hugh's PMA, Pamco H/O, 3 way valve job and clean up the ports a bit. It was also suggested that I use an adjustable cam sprocket? Thanks again.

 

[XSLeo]

I think the mags are very heavy.
The only bolt on adjustable cam sprocket I know of is on Mike's performance cam. From what I hear the way the cam is made where the sprocket bolts on makes it vibrate.
The way a stock cam is made you can adjust the sprocket by pressing it off, turning it slightly and pressing it back on.
Leo

 

[yamimoto]

Thanks XSLeo. I would prefer wire spokes but I also want a disc on the rear. I have wire spokes but they need to be rebuilt, the hubs may be the only useful parts, not sure at this point, need to examine them. The mags are ready to go.
Regarding the cam, sounds like I should stick with the stock cam, already have XS vibration.
Shurlok