Topic: 1975 tach trouble

[johhny b]

I was having an over reving problem, and through the boards help deturmend i had the wrong tach. i got one off of ebay from a 1972 and it is a different setup then mine. the one that came with the bike has a green face and is held onto the chrome bottom cover by two studs coming from bottom of tach. the one i got from ebay has a blue face and apears to attach to the bike by a clamp that goes around the tach. are 72 and 75 different, where can i get a correct tach.

[Clyde]

It sounds like you have a 1972 K2 tach. If there are indicator lights in the tach then it is of a 1971 K1. If it is plastic and with lights, then it is a K0.
These three gauges all mount with a chrome clamp  and a rubber sleeve direct to the top triple clamp. Whereas the later ones have two 6mm bolts which hold them on to the gauge plate, which mounts on to the top triple clamp.
K2 tachs are pretty rare, so it is probably worth putting back on to eBay and getting the right one. They changed from 73 onwards.
Any tach from a k3-K8 or F1-F2 will fit and work OK, but there are differences in dial face colour and the red zone.
K3-K6 had red zones starting at 8000rpm and F1/K7/K8 had a red zone starting at 8500rpm. F2 were I think 9400rpm.
Also K6 and F6 were a lighter green than the others.

[Raul CB750K1]

Apart from the difference in holding or not the idiot lights and the position of the redline, I would say they should be just compatible as long as they have the same gear ratio. Could it be that you have a tach from a different bike?

Raul

[johhny b]

the 72 tach has a round piece coming from the bottom about an inch and a quarter long where it attaches to the cable. it attaches to a bottom plate by two tiny screws, and attaches to the bike by a clamp. it has a blue face.the tach on my 75 is belived to be originaly from a 550, it has a rectangular piece about half inch high where it ataches to the cable,it has two studs coming from the bottom where it attachs to a chrome bottom cover. that attaches to the gauge plate by two small bolts, it has a green face.            I hooked up the cable to the 72 tach and it worked, so it has the correced gear ratios.do i have the correct set up for my bike, or has somebody changed it a one time.is a latter model 750 tach the same as the one i removed from the bike, so i can drop it in. has anybody got a correct tach for my bike that they will sell or trade for the 72, or 550 tach or both. or does someone want to buy the 72 tach.

[Clyde]

I would stick with the later mounting type tach. Whilst the ratios are the same, it is messy to fit a different year tach and maintain the look. The chrome covers mounting is different as you have mentioned.