I have an Onan 5500 on my road warrior. It doesn't start well and won't stay running. When it's cranking white smoke comes out. I pulled the carb and cleaned it, gas tank was less than 1/3 full previous owner said he treated the gas with sta-bil. I filled the 30 gallon gas tank and added a can of sea foam. I can get it to run after messing with it for a while. I also replaced the spark plugs, they were pretty black. Thank you in advance for any help. My RV place ordered me a new carb, they seem to think that'll fix the problem.