Decompression button location

Guys,

Dropping my cylinders off tomorrow at Hall's, for boring and new pistons and rings.

On 390, 500 and 430, I have decompression buttons on hand.

Where is the best placement for these in the cylinder liners. In other words how far down from top of liner?

I'm going at an angle, carb/kicker side between the stud holes and regular head bolt location.

Looks like there is plenty of meat in almunium outside of liner for them.

Thanx

The hole on my Maicos which come stock with the decomp valve in the cylinder are close to the top, I did not measure them but I'd guess no more than 1" from the top.

KW! Thanx million!

Suzuki TS400 measures about 15mm from top.

Equal distance from top cylinder and top of admission hole on my 500 AE.

Thanx guys! I appreciate the help!

Put them in the head. Very convenient for starting. Need to avoid the pipe. Have done a couple like this with success. 500AE and 390AMX

I just ordered a counter bore so I can drill a hole for the pilot and use a extended pilot to bore into the fins and make a flat spot on the surface then drill and tap it for the decompression valve. Next I need to purchased a radial arm drill press to do the machining. I figure for $300 and I have so many compression valves to install it will pay for itself. I just purchased a nice craftsman drill press with a work table that angles for $239 / with free shipping can’t beat that with a stick.

Do you use the spark plug threaded adapter that has the 10mm threaded hole for the compression release or do you tap the 10mm hole in the cylinder or head.?

I notice the 500 in the pic uses the 10mm-1 threaded compression release in the cylinder. There is a heli coil kit for the 10mm-1 thread if we get into trouble should the threads pop out. Good to have a backup plan.