I have a 4kw onan in my Coachmen classic. It only has 183 hours on the meter. The problem it has is that after 20 minutes to a half of running great it slows and smokes big time. Let it cool off for an hour or so and it will fire right back up and do it again after half hour or so. All normal stuff checked, cleaned carb ect. Any ideas would be appreciated. Thanks Todd