1051.5—Which engines are excluded from this part's requirements?
        
        (a) 
        
        (1) 
         You may exclude vehicles with compression-ignition engines. See  40 CFR parts 89 and 1039 for regulations that cover these engines.
    
    
        
        (2) 
         Vehicles with a combined total vehicle dry weight under 20.0 kilograms are excluded from this part. Spark-ignition engines in these vehicles must instead meet emission standards specified in  40 CFR parts 90 and 1054. See  40 CFR 90.103(a) and the definition of handheld in  40 CFR 1054.801.
    
    
        
        (b) 
         We may require you to label an engine or vehicle (or both) if this section excludes it and other requirements in this chapter do not apply.