I have a 1972 Yamaha R5,made into a three wheeler(ATC).What is the correct fuel/oil mixture??

turning the screw way out makes the mixture lean, so the problem must be the carb is too rich.
check all the jets were installed correctly when the carb was cleaned
make sure the carb float bowl is not flooding.
Check the fuel tap is working correctly.
make certain the airfilter is clean.
check the engine has correct amount of clean oil( not fuel contaminated)

This unfortunately is a problem with carburetors on a Yamaha. The float sticks and allows fuel to seep past the needle valves and it ends up draining into the cylinders where it escapes past the rings and down in the oil sump. You are going to have to work on your carburetors and put a positive cutoff valve on your fuel flow or repair your automatic cutoff petcocks. You also will have to drain the oil sump and put fresh oil in as the fuel/gasoline mixture is too thin and may cause a fire.

Two essential problems: 1. Automatic petcocks not working properly, and 2. The float is not cutting off correctly.

generally this is what i do. warm up engine. shut down and count the number of turns to gently seat the mixture screw. jot that info down. Then remove the mixture screw and spring. spray carb cleaner in the hole for the mixture screw, using the straw that comes with the can. this will ensure you have a clear circuit. Replace the mixture screw and spring and set back to original setting. Start engine. now you can adjust mixture. turn in or out to achieve maximum RPMs. blip throttle to make sure there is no flat spot at that setting. if it sounds good then back out the screw 1/8 more to have a slightly rich mixture. That should do it

most of those little hondas are 2thou inlet 3 thou exhaust

20w40 motorcycle engine oil, the same as a four stroke motorcycle would use,
Not car engine oil as this can cause the clutch to slip.

Sorry .couldn't tell you. about the frame or style but if is an engine or electrical problem
bring up some detail about it :)