Chewie,
The water trick works in a running engine for light deposits. Just use a spray bottle on mist and you won't have to worry about hydrolock.
A really experienced Honda Mechanic from the Old Days who used to work at Pete's Cycle in Md. told me this trick.
If the engine is in the frame and runs, remove the airbox, remove the rubber bellmouths from the airbox and re-install them on the carbs.
Warm the engine up, and using a tea/soup spoon as a measure and scoop, throw a spoonful of UNCOOKED rice in a carb's bellmouth while holding revs at about 3K.
Do this a few times for each carb, blipping the throttle occasionally to clear the pipe!
When you can see shiny aluminum through the plug hole, you're done.
Take a shop vac, put it on your tailpipe(s), and rotate the engine by hand to allow each cylinders valves to overlap so the vac can suck any remaining rice out.
Put everything back together.
The rice is softer than the steel and aluminum, so no damage is done as long as you keep the amount of rice on each "toss" down. There is a very real danger of bending rods due to ricelocking if you are not careful.
Here is a method I personally have experience with, that works rather well. I learned it from our four-wheeled Honda brothers at CRX-Perf.org.
Cut four 1 foot pieces of coathanger or other stiff wire. All 4 pieces need to be of an identical length.
Pull all four plugs.
Take your wire pieces and put 1 in each plug hole.
Rotate engine by hand until all four wires line up, meaning your pistons are all at the same level relative to each other.i.e. at the center of the cylinder.
Remove wire, fill each cylinder with ATF, yes, just plain old ATF, and let soak. Heavier deposits require longer soaks of course, but most people just let it sit overnight. I did 24 hours on my CRX.
Using a vac or siphon or whatever, drain all 4 cylinders as thoroughly as you can! The next step will be less messy.
Leaving the kill-switch off, crank the engine for several seconds at a time, blowing the cylinders clean. You can pack shop rags or paper towels over each plug to soak up what comes out, but you will need to weigh or wire them down as your engine will blow them out.
When hardly to no ATF appears to be blown out, re-install the plugs.
CHANGE YOUR OIL AND FILTER NOW!!!!!!!!
It is my experience that 750 clutches do not like ATF. The organics tend to swell and lock the clutch!
Push vehicle outside, or use an exhaust tube to route it out the shop door, but don't do the following inside!!
Start the engine and run her until she stops smoking.
You are done.
Of course, if you are tearing down the engines anyway, then you just make a shallow cup out of tin foil and soak each piston upside down until the carbon comes off. No need to worry about evaporating with ATF either.
