Coleman HS400UTV-2 Owner's Manual page 164

8-60 Periodic Maintenance and Adjustment
Table5: Solution of Common Problems in Engine System
Idle speed cannot be
1
adjusted.
2 Idle speed is not stable.
Loss of power
3
performance.
4 Popping noise in engine.
5 Engine is difficult to start at
Check throttle cable for seizure
Check the adjustment knob of carburetor for damage or wear
Check the needle of carburetor to see if it can be placed to the
bottom
Check if the high-voltage wire is in poor contact.
Check if CDI s faulty
Check if the carburetor or fuel filter is clogged by debris.
Check and clean core of air cleaner
Check muffler and spark arrestor for blockage, clean spark
arrestor if necessary.
Check air cleaner and admission line for leaks.
Check muffler to engine connection, make sure it is not loose.
Check octane rating of gasoline, it may be too low.
Check if the battery voltage goes down when temperature