I want to cap off tachometer hole - what thread size?

I am not using a tach & want to cap off where the cable connects to the engine. Can I just screw an acorn nut over it to cover it up? If so, what thread size? Thanks!

I did this little surgery on my 650 head when I put in the 750 Gpz cams that didn't have the tach drive. Had no luck matching the pitch on the threads as they seem like a pretty coarse, oddball size.

My first attempt was with a cast galvanised pipe cap that I picked up from a plumbing wholesale supplier. I coated the threads with Seal-All, which is an oil and gas-proof, automotive adhesive.

This worked not too bad but I didn't like the look of the cap which kinda seemed out of place. I decided to simply re-install the tach cable (without the pinion gear or inside cable) and put a little dab of two-part epoxy glue on the threads. This allowed me to keep the stock look with the tach cable connecting from the head to the non -operational tach. No problems with any oil leaks.

I like the stock look and for anyone who knows these old engines won't suspect that I have any interior upgrades. Just trying to keep the sleeper theme going:-)

Cheers-Colin Firth-Ontario Canada
1977 Kz650 Custom. 810 big-bore, WG Mikuni 29 Smoothbores, Gpz750 cams, Gpz 750 intake valves, ported, polished and milled 650 head, Velocity stacks, Lower gearing, MAC Pipe, 130 rear tire, APE cam chain adjuster and lots of other goodies. Stock looking Moondust Silver paint job. Miss January on the 2007 Kzrider calendar.

I don't want to use the cable at all as I don't have any gauges. Anyone know the thread size? Or anyone come up with a way to seal it - well?

You should put your bike in your signature line so people know which bike your talking about. Anyway, I picked up one of those plugs from Jeff that fit in the hole. It is for a 1000 so you might want to start at Z1 to see if someone makes a plug for your bike.

well my bike is not stock at all so you would not even recognize it!

It just plugs in there & stays??

I have done this twice.
Just take your old tach cable and cut off the end.
Slide off the 'nut' that crews onto the head.
Fill it with silicone and install.
Makes a nice permanent fix.

That would work IF I had a tach cable. I don't. I don't want to pay for a new one just to cut it up. Does anyone know the thread size?

try a local bike wrecker.