I am new in here and hoping someone can help me. I have a 150cc 4stroke Ricardo. It was starting full throttle and there was a piece broken off the carb, so we replaced the carb. Now it starts fine but will idle up and down on its own unitl it idles so low it wants to die. It does have a new carb so what else can it be? The air filter seems clear and we have adjusted the idle. I cant figure it out

 

K amberdavis1975 really not enough info. However possible mixture isn't right.. Dennis

 

" it starts fine but will idle up and down on its own" could be caused by 2nd-air leaks into through some gaps at fitting portions between In-mani and Carb, or In-mani and Port of cylinder-head. It's just my guess based on experience.