Section 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. 70 FR 40486 , July 13, 2005, as amended at 73 FR 59245 , Oct. 8, 2008