Tyl3r wrote: 02:04 pm Jan 01 2024
RE:CONFIRMED - I did not have a plug to measure and compare when I originally did this, but thanks to Kawibunga for the detective work and comparison to an original part, the correct thread spec for the plug is 3/8" BSPT (update 1/1/24)
CONFIRMED! The thread size for the coolant plug on the underside of the cylinder is most certainly M16x1.5. I tried a 3/8" NPT and it would start into the hole but stop. Here is a link to a plug if you need it, got mine from Belmetric, saw that Fastenal also sells them: https://belmetric.com/stainless-taper-m ... P16X1.5TSS
FYI that link is still for the M16-1.5, not the 3/8" BSPT plug.
Here is the link from Belmetric for the 3/8" BSPT:
Chuck, Kawi, Tyler: thank you for your efforts. Really appreciate the verification & hyperlink immediately above. Gonna go ahead and order 2, just in case. billie
It's plain carbon steel. I didn't want stainless or black carbon steel.
I've since learned that Japan manufacturers routinely and historically use British taper thread plugs. Use of this non-metric hardware is nearly universal and there may not actually be metric taper threaded plugs.
The plug we think we need is available from many vendors and may even be in available in better stocked hardware stores because even lawn mowers from Japan manufacturers use BSPT.
oh, I dunno. Looks like the tapeted plug that's in my KDX cylinder is plain carbon steel (not stainless, not black iron). If it's necessary to install one of these plain steel plugs, then high temperature anti-seize compound will be applied to the threads. I had two RZ 350s in the past. The 6mm threaded bolt coolant drain in the side of the cylinder were plain steel. The coolant drain plug at the water pump on my two DRZs are the same. I don't remember, does KDX have (plain steel) plug at it's water pump?
In contrast, many of the aluminum fluid housings on my BMW motorcycles use stainless plugs. Each of my two BMWs, as well as an earlier one, have 3 stainless plugs each (final drive, transmission, engine oil).
