Had a seizure !!! BVF main jet size and jap equivalents ?

[keleto]

Had a high speed heat seizure (on my ETZ251) so after limping home for 40 miles at 30mph I have been weeping and polishing my poor bore and piston back to usability. I know my oil pump and ignition timing are good, and my plug color is fine. I have never had any indication of a heat problem until I started pushing it on the dual carriageway so I suspect my main jet might be too small. Also, I recently installed a morris minor air filter which may have weakened the mixture.

Anyway, my current main jet (in a BVF 30N3-1) is stock 130 size. I think that at some point MZ started using 135 as standard, so to be safe I might increase it to 140. Does this seem reasonable ? Also, does anyone know the mikuni/keihin equivalent size as I have a lot of jap jets kicking around which use the same thread. Not much point buying one if I already have one which will serve, but i do not know how the BVF vs jap sizing compares.