Topic: Front suspension 78F vs78K

[VI Rider]

I found a donor front end from a 78K that I'm thinking of using on my 78F. So far I know the top triple tree is the same on both bikes and the springs are the same as well. The seller of the 78K says I don't need to worry about the twin disc setup on the F because it'll bolt on to the 78Ks forks.

I like the look of the 78Ks front end more and it will give me another triple tree I don't need to feel bad about cutting up.

My questions are...
1) Will the brake callipers from the F fit on the K? (I've noticed the K has the calliper mounted in front of the forks while the F has the callipers mounted behind the forks.)
2) Will my wheel fit in to the Ks front end? (Both fork are the same distance apart.)
3) Is there any difference in performance of the suspension between the bikes? (They use the same spring but I don't know about oil/valves.)

Thank you guys and gals! I've been lurking here for a while and you've all helped me out so much already! I just haven't been able to find an answer for these questions anywhere else.

[Don R]

 I believe the brakes are different. Maybe someone can elaborate.

[Mr Freeze]

A 78 F front end and wheel with dual discs has the calipers mounted on the back edge of the fork leg while a '78 K has the caliper mounting on the left front edge with that floating arm. The internals of the forks suspension wise are the same and the wheels are the same. The F calipers are of a totally different design so that won't swap. The only thing you'll have to do is change the F discs out for the K one

[seanbarney41]

f3 discs and k discs have a totally different bolt pattern, so that won't work

[martin99]

Not sure I understand what the OP is asking. How does the 'look' of the K differ from the F, other than one has a wire wheel and single disc, and the other a comstar and twin disc?

You can achieve the look of the K by quite simply changing out the complete front end, but obviously you'll need to compromise and go to a single disc. You then have to find a spoked wheel for the rear too.

If you want to retain the comstar and twin disc set-up, you may find that the fork lowers are interchangable but I cannot see what you would gain by doing this. If you are looking for a twin disc, spoked wheel front, you may want to consider a GL1000 front end as others have done.

[VI Rider]

you may want to consider a GL1000 front end as others have done.

I've been looking for one but no luck yet. I guess I'll just use the stock front end and forget about that K front. Cheers

[MiGhost]

you may want to consider a GL1000 front end as others have done.

I've been looking for one but no luck yet. I guess I'll just use the stock front end and forget about that K front. Cheers

Both the F,and K share the same front axle (182mm c-c). So the the K forks will mount into the F tree. To carry this into the dual disc. You just need to add the additional rotor and caliper.

On another note. I am looking into the possibility of using GS550/750/1000 rotors on the CB550/750/GL1000 spoked hub. It is looking like some minor machining to adjust the spacing on the rotors. Then figure out the speedo drive to work with the comstar style forks. Which interestingly enough. Honda did away with the small nub that holds the speedo drive on the dual disc comstar forks. Maybe it is not necessary after all??