I HIGHLY recommend that before attempting to remove the carb holder screws you soak them for 3 days with Kroil. On my KZ650 I did that and the screws came out with no problem at all. Otherwise you run a very serious risk of either breaking the screws, breaking the cylinder head, or damaging the screw heads. I've seen postings where other folks have done that type of damage by trying to force those screws out. Ed
I replaced these with allen heads many a year ago.
1978 KZ650 b-2
700cc Wiseco kit 10 to 1.
1980 KZ750 cam, ape springs, stock clutch/ Barnett springs.
Vance and Hines Header w/ comp baffle and Ape pods, Dyna S and green coils, copper wires.
29MM smooth bores W/ 17.5 pilots, 0-6s and 117.5 main
16/42 gearing X ring chain and alum rear JT sprocket....
I bought a BSA engine once and the screws that held the case covers on had been replaced with Allen head screws. Every one of the female threads in the engine that those screws fastened into were stripped! Remember that aluminum engine threads will always strip out before the steel screw threads, so if you use Allen head screws be very careful not to overtighten them because apparently that is very easy to do. Ed
I've been using Q-tips to apply Liquid Wrench all around the fasteners for a few days now. The top fasteners are blind but the bottom ones are exposed, so I've been hitting the back of the bottom fasteners with Liquid Wrench as well. I just bought a set of 1/4-inch JIS bits (#1 thru #3) as well as a ratchet set with a 3/8-inch drive to 1/4-inch bit adapter that should come mid- next week. The plan is too keep on applying Liquid Wrench every day until the bits /ratchet arrive, then take out the carbs and attempt to remove the fasteners. I also got some Loctite Blue 242 and plan to apply them to the bolts when I install the new holders.
I had to use a vise grip to get the last stubborn screw out. I turned it very slow to not break the head off the shaft. I replaced all four screws with new JIS bolts from Z1 enterprises and used Loctite to seal. Everything has been running good so far.