Get a coat hanger take out the petcock and start digging and flushing. What happens to these engines over time with neglect is crap builds up around the rear cyl and they tend to over heat with no coolant flowing around the cyl. You must open it up. Good luck. You may have to take off the water pump to get more stuff out. Time spent cleaning will pay dividends.

"Drugs are money, money is power, power is security." - Kent Heiner
Nedrow population 2212
Carbon footprint family of 2/11 tonnes of CO2/yr