Topic: CB400F Speedo on CB750

[Scrubs]

I am taking my front wheel down to a 18" so for a correct speedo reading I read in some posts here that installing a speedo drive from a 400F will fix that problem as it shares the same front wheel size. I just bought one but am struggling to see how it will fit.... The stock 750 speedo has two tabs sticking out on the plate and the 400 has two slots, Sort of a female version... How have other people gone about  this? Do you use the whole speedo drive housing? or just the internals or vice versa?

[bwaller]

Use the whole speedo drive assembly. The internal parts won't fit in the 750 part.

[Scrubs]

Thanks,

The whole thing doesent seem to fit, unless I am over looking something... 
Do I also remove the 'stock' (750) plate that has the two metal tabs?

[bwaller]

I used the 400F speedo drive on a 550 hub (same as the 750) on which I'd laced an 18" rim. The 400 piece was the same size as the bigger bikes except the internals were different obviously. I used the modified plate with the two tabs and the 400F speedo drive.

Not sure what doesn't fit, any chance for a picture??

[Scrubs]

Thanks Bwaller,

I can theoretically see how it might work but I am unsure of which part needs swapping or modifying.


Here is the stock cb750 - a little dirty to make out but in the bottom -as you know - there is a plate with two male prongs.



and here is the 400f one: which has two female prongs that sit at the top of the drive.



that female plate makes the busing too large so I assume you remove it remove it like so.
to give the correct space in the 400f drive:



Here is that part I removed from the 400f - is this the peice I need to modify by trimming it down and giving it (bending out) two male tabs at the bottom?
 

[Scrubs]

Just giving this a little bump so it doesent get lost.

[bwaller]

Hey Scrubs,

Did you actually remove that from a 400F, because I don't think it is. 400T maybe?

The one I used looks exactly like the 750 piece.

[Scrubs]

Hiya bwaller, No, I bought the sucker from a breaker on ebay 

Guess the seller lableled it wrong or it was a later model or something.......
hmmmmm...What part did you modify anyway? gonna have to find another I guess. Piss. I paid too much for it as it was 

[bwaller]

The roughly modified drive plate on the right!

I only have one more 400F speedo drive, but need it. Run an ad in the wanted section here, you might get lucky.

[Scrubs]

Cheers, Bwaller so just to clarify. Did you take the gearing out of the 750 drive and place it in 400f drive?

[Scrubs]

Ok just found another one that looks like it will do the job from a 250G5 I have seen a photo of the rear and this one appears
to share the same look of the 750.

I cross referenced the part number and here are all the models that share that same speedo drive as the 400F