# 420 john deer



## Mowerman54 (May 1, 2019)

i have a 420 john deer 20 horse twin onan runs rough, hunts spits and sputters for about 10 minutes an then it will take off running fine can anyone help me with this?


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## RC Wells (Dec 26, 2008)

The Onan engines generally require carbon removal after a few years. What happens is they build up carbon on the heads and piston crowns, then run really rough until they warm thoroughly.


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