Interchangeability of Speedos and Tachometers within CB750 models

[Pedro26]

Hi,

Can anyone let me know if the speedometers and tachometers are interchangeable between the CB750 models?

Background I have a USA spec 1975 CB750F supersport (bought from AP motorcycles in Matlock). I did the main mechanical restoration work back in 1998. At that time David Silver spares used to stock both the original and pattern versions of them. The genuine speedo was £95.00 and the genuine tachometers US style was £69.00. Replica ones were less than half that. I’d planned to do this more comestic finishing work at a later date. I thought I might run to the genuine ones eventually. In 2002 the bike was stored, and it’s only now that I’m finally able to do that work.

However, now David Silvers  can only source new genuine speedometer for my model and it’s now over £500. I can’t justify spending that on a Speedo. However I’ve seen new speedos and tachometers replicas for the 750k series SOHC Hondas at sub £100 prices. They look ok and are only missing the ND logo.

I’ve seen other people open the originals up, and service them, putting a transfer on the face, but the  face of my Speedo dial has puckered away almost like it’s been heated in an accident. Also the crimped on chrome ring is difficult to remove and replace well. Not impossible to physically do with patience, care, improvised tools, a jig and tube clamp. (A Dutch guy seemed to have a better smooth pipe clamp than the normal jubilee clamp.)

Anyway, I thought put on the pattern ones if compatible and save the originals for the bike’s future owners. That is if they fit etc.

I hope somebody on here can advise.

Thanks in advance.

[Deano400]

I don't know about the interchangeability of the clocks but Peter Horton, Kent400 on here, is the man for clocks. Having done a set myself I decided once was enough and sent the next two sets to Peter, came back like new.

[McCabe-Thiele (Ted)]

Peter Horton has done my 400 & 500 clocks very happy with the results.

[Sesman]

Peter is the ‘Boss’. Had two sets done 👍👍

[Oddjob]

100% agree with above comments. Peter has boxes of broken speedo/tachos, so even if your facia is unsalvageable it's possible that Peter will have something he can use as a replacement. Superb work, and if you knew me you'd know just how good that it coming from me, he'll take it apart, re-zinc the base (which may look ok from the outside but be rusty as hell on the inside) fill the damper pot to stop the needle bouncing, repaint the needle and reface the facia. He'll also respray the outer dish, comes back as good as new. He has a special machine for recrimping the ring. And the cost is usually less than DS wanted originally for a genuine one.

The only down side is how busy Peter is, might be a few weeks before he an return it, won't know without asking.

[McCabe-Thiele (Ted)]

True Ken - if I was being super critical it's a shame that the mileometer tumblers remain an age related yellow-white plastic as otherwise it would have all the appearances of being a brand new clock. I guess that would be either extremely expensive even if the tumblers were available.

[Oddjob]

Just a new decal needed Ted, they are a strip of numbers wound around as far as I know.

[McCabe-Thiele (Ted)]

As it's only for the tenths of a mile section it's fine with me - in a way it reflects their originality status.

[SeanFD]

Peter did some guages for me and we (He) replaced the thenths numbers - it is a strip wound round.

I can't remember now whether he supplied them or I did - I think the latter -  but they weren't an exact replacement. He cautioned that they might unstick with time, but so far - 2 years I think - all is well.

As far as I know - fairly close - the innards are all the same (Peter could confirm this) unless you are changing MPH to KPH or vv. The thing to check is how the chrome bottom is fitted and how the clocks are mounted. After K2 I definitely know it changed.

[Oddjob]

If you're using your original gauges then it's not a problem on compatibility.

[Pedro26]

Thanks for the suggestions, but does anybody know if the K series gauges are interchangeable with those from the F series? I understand that there were cosmetic changes between the different K models.

Mine look like the later gauges in Sean pics, two ‘acorn/dome headed nuts on the back. Well from the back at least.

So maybe anything post K2 will fit.

I could get the replicas, fit them,  and have a word with the repair guy on the forum about having the originals sorted. Removing the original gauges, now knowing what to look for, I can see both have been opened up before, leaving the telltale signs on the crimping ring backs.

[kent400]

The replica gauges are best avoided. They are basically a copy of a Nippon Seiki mechanism and none of the parts are interchangeable with an ND gauges. I've been 'gifted' several of them where the owner has subsequently found genuine ND gauges and found the replica ones wildly inaccurate. Gifted on the idea that I could use them for parts but there's no chance of that!

One request from an owner of replica gauges to fit faces which have ND one them but the screw holes on ND faces don't line up with the securing screws on the replica ones.

In view of the fact it's possible to obtain parts for F2 gauges restoration is a better plan. Early ones with the angle drive mechanism (KO & K1) often suffer wear in the plastic gear within the angle drive mechanism and the steel gears that drive the mileage counters.

A warped dial face can sometimes be flattened by warming with a hot air gun and once warmed pushed on a flat surface Only done that once for a very well known Honda parts supplier on a machine he sold.       

[Pedro26]

Current speedo

[Pedro26]

Current tachometer

[Pedro26]

Both function well. Well that is back in 2001, the last time the bike was rode.