Hello - I'm slowly rebuilding my green 1970 CT1 175 and the engine is apart waiting for a crank rebuild.  Meanwhile I found a very nice 1973 CT3 front fork assy to take apart so I could my worn out fork tubes. But since I got everything from the slightly beefier triple tree, to the matching hub brake plate (to match the aluminum fork slider), and all was in great shape, I thought I could discretely install everything, while using all new Yamaha steering bearings and rings at same time for good measure.  But as I was rigging everything together, I'm discovering the slightly thicker CT3 triple tree upper and lower portions won't allow the CT1 painted headlight bucket brackets, and bits, to install.  Does this all make sense?  It seems like I either need to stay with the older, CT1 Tree or cut the brackets...which I don't want to do.
Thanks for any ideas or clarifications.
Joe M

The upper looks to be the same part number...  lower is different.

Any reason you can't use your original triples with the new forks?

Hello - I will post some pics tomorrow. Yes, I see part numbers are same when referencing at least partzilla, but in reality the parts in the two diagrams are different show the later part having built in handle bar clamps and the early part with separate "bar riser" style clamps. The later part is also more massive and has bigger fork clamps and bigger bolts. The bigger clamp (height, not dia.) is about 1/8" more, and prevents the headlight bracket from slipping in to position when I try to prefit it with its associated rings.
In the end, maybe I will simply clean up the original tree assy but always thought these parts could be swapped out with no issue.
Regards,
Joe Mulqueen

I think you'll find the headlight ears or covers, whatever you want to call them are longer on the pre '71 models because the lower clamp on the triple tree is single bolt and isn't as thick.
 

Yes, the uppers could be different design and yet compatible.  Parts lists don't show the lower as compatible.

You could also use headlight mounts from the later model?

Not the best arrangement, but here are pics of the CT3 lower assy mounted on my CT1B and then it's top portion along with the smaller CT3 Tree parts on the workbench.  For the CT3 Tree both top and bottom portions are bigger castings with bigger and more pinch bolts   Since I want to keep my original green headlight bucket brackets, and not cut them shorter, I will probaby keep with my original CT1B tree assy with the takeaway that a CT3 Triple Tree is not compatible with a CT1B's headlight brackets.
Regards,
Joe.

Hey I have a 71 Ct1c that has the same trees as the Ct3 upper and lower with 2 bolts

Can you take off the headlight brackets and measure how long they are?  Just kidding....

  

hope this helps 

CT1c had the "upgraded" triples of the CT2/CT3 if I remember correctly.