I have a 02 pit (107 incher)When im driving down the road at any given speed the carb seems to cough briefly just 1 quick time each time.Also there is an oil residue on my oil can every time i ride.The coughing does not effect the bike much at all.Is this common.As far as i know the carb is stock .Doesnt smell to rich to me.I had it adjusted last summer and the guy said it had grat response(i think so too)What do yall think?
If your carb is coughing at steady speed, you might have an intake leak. Inspect your spark plugs to see if they are burning evenly. If not, the lightest or cleanest plug will be on the cylinder that may have a leak.
The 107 was dual vented. One line went from the bottom end breather (behind and below the oil pump) to the back of the air cleaner and both heads vented through banjo fittings into the back of the air cleaner as well.
Inside the rocker box covers there are a couple of umbrella valves (directly above where the air cleaner mounting bolts go into the heads. Sometimes those umbrella valves get stiff over time and don't seal well or sometimes one will roll and not seal at all. This will cause oil mist to transfer into the air cleaner.
Prolonged high rpm operation will result in oil carry-over into your air cleaner as well.
On a dual vented engine, you can plug off the top end breathers all together, or you can route them away from your air cleaner.