Topic: The Great CB750F0 Fork Mystery.....

[Neuxstone]

I could write a book about all the anomalies I've found while doing a frame complete rebuild on my '75 F0, but I don't want to relive what I've been through.
 The second set of fork tubes I ordered (51410-341-702) for it were incorrectly listed for my bike on the 4into1 website as fitting the F0, so I did some digging. they insisted they were correct for the bike, but after digging for some hours I found my bike needs fork tube 51411-392-003.
 The sales/service person said someone switched my forks from another model (assuming he could be right), but I couldn't find any Honda models with the (35mm) dia. configuration going thru all the parts books. Which leads me to believe the F0 and F1 have the oddball forks.
 
 Does anyone out there Know the configuration of the early "F" forks?
 
I took pics of the "K" forks next to my, what I assume are my F0 tube bottoms. (having trouble with attaching photos from dropbox)
You will se the bushing at the base if the fork is smaller on the "old fork" and the undercut is only a couple inches from the bottom compared to the "new", or K fork I was sent. 

[scottly]

The F0,F1,K7,and K8 shared the same forks, which had longer lowers than the earlier K bikes.

[HondaMan]

The F0,F1,K7,and K8 shared the same forks, which had longer lowers than the earlier K bikes.

...and that 'nnnnn-392-nnn' part number...

[Don R]

 I believe the F0-1 replacement tubes are an inch longer than the 72-76? K. There was a set in the for sale section recently. 23 13/16"? They do interchange. I noticed some of the internal parts were different but fit the same tubes. 
 

[Don R]

 Forks by Frank also look different but fit and work fine.

[Neuxstone]

Thanks all...
  I'll try Frank, but from what I'm hearing from ya'll is these must've been switched out by some masochistic person in the past...
I'll Keep this post up for another day or so to see if anyone ran into this. BTW these are the shorter version, so spring length wont allow the longer tubes.

[newday777]

Thanks all...
  I'll try Frank, but from what I'm hearing from ya'll is these must've been switched out by some masochistic person in the past...
I'll Keep this post up for another day or so to see if anyone ran into this. BTW these are the shorter version, so spring length wont allow the longer tubes.

Don't take it down.  Someone may not have seen it that Don't come around often.....
And it's good for reference

[scottly]

I could write a book about all the anomalies I've found while doing a frame complete rebuild on my '75 F0, but I don't want to relive what I've been through.
 The second set of fork tubes I ordered (51410-341-702) for it were incorrectly listed for my bike on the 4into1 website as fitting the F0, so I did some digging. they insisted they were correct for the bike, but after digging for some hours I found my bike needs fork tube 51411-392-003.
 The sales/service person said someone switched my forks from another model (assuming he could be right), but I couldn't find any Honda models with the (35mm) dia. configuration going thru all the parts books. Which leads me to believe the F0 and F1 have the oddball forks.
 
 Does anyone out there Know the configuration of the early "F" forks?
 
I took pics of the "K" forks next to my, what I assume are my F0 tube bottoms. (having trouble with attaching photos from dropbox)
You will se the bushing at the base if the fork is smaller on the "old fork" and the undercut is only a couple inches from the bottom compared to the "new", or K fork I was sent.

First of all, 4into1 isn't the best resource for parts fitment information. It would help if you could provide pictures of what your original fork tubes look like, as well as what you were sent (twice??). ALL of the 750s had 35mm fork tubes. I'm not sure what you mean by "bushing" at the base? These pics are of a K7 tube, which is the same as the F0/F1, with the 392 part #. What does the 4into1 site show for a K7 or K8?

[Don R]

 I've noticed a difference inside but assumed the internal measurements of the fork tubes were the same and the outer measurements of the damper rods contact areas allowing different damper rods to still fit. But I did only assume.
  In my case I was using the 21 13/16" long #341 fork tubes for a 550. I've found the 341 number forks with 550 and 750 tubes. Since I was also lowering it for drag racing I didn't use the longer F0 lowers.