Here's a tough one!
Does anyone know the length of the tacho drive needed for a 1969 Starfire?
I bought what I thought was the correct drive, but the inner shaft had been removed from the outer casing. When inserted, it's obvious that the inner shaft is about 1 inch too short.
Doing some research it appears that there are two different lengths, maybe one part is for twin engine and the other a single? Who knows?
The outer casing I have is 3.5 inches long below the mounting flange. I can source a new casing that's 2.5 inches below the flange, so that would mean I can make a complete short unit, however I don't know if that's what I need.
Short of shoving something down the hole to try to measure the depth, which seems unreliable, I'm a bit stuck
It's not off an A65 - that one plugs into the end of the oil pump and does not need a drive gear on the end of the tacho spindle.
Just doing a crude measurement off a crankcase picture, shows the distance from the outside of the crankcase, where the tacho drive body bolts to it, to the centre of the crankshaft oil pump pinion that drives the tacho is about 3.25". In other words, the distance from the underneath of the tacho drive mounting flange to halfway along its drive pinion is about 3.25".
This measurement would seem to indicate that the long body you have is too long?
Thanks Spaceman. I got myself in a pickle measuring this quickly earlier.
The casing I have is 2.5 inches under the mounting flange. The problem is, the shaft is also 2.5 inches from tip to the top of the splined 'cog'. Meaning the square hole is about an inch down inside the casing and that the groove for the securing pin does not align with the hole in the outer casing.
Looking more closely. The pin that holds the spline to the shaft looks a bit butchered. Not sure what I've got but it seems the shaft is the problem and not the outer.
Trying to attach pics
Here's a picture
It therefore looks as though the spindle has been reduced in length by about an inch and the drive gear then pinned back on? As with many BSA parts, you could probably buy a replacement from the USA but getting one in the UK looks difficult. Although you would need the right engineering skill, I don't think it would be that hard to repair the short shaft and extend it by about an inch?
I agree. I can't think why anyone would shorten the shaft, these might not even be an original pairing, we can only guess.
It's beyond me to lengthen the shaft and re attach the gear
Pity. These tacho drives are hard to come ny
Looks like you have the spindle from a 1972 tachometer drive which was redesigned and shorter than the 1969-71 item.
It's possible to make a spindle from a piece of 5/16 silver steel if you have a lathe.
I think the challenge might be making the square hole in the tacho cable end - I had a think about how I might do the machining (I have a lathe) but, without resorting to using a square mandrel and some form of forging, I couldn't think of a way of making the hole?
It's well beyond my skills. The vendor has refunded me.
The outer casings are available, it's the shafts that are scarce.
It's not that important to me, if one comes along at a price I'm happy with I'll do it, otherwise it can wait.
Appreciate your input fellas