Small Engine Emission Requirements


What are the Federal EPA and California C.A.R.B. emissions requirements for small gas engines, specifically small engines used with motorized scooters; (i.e. GoPed, Bladez, X-Treme Scooters, etc.). I'm looking for the full emissions requirements including the maximum amount of particulates allowed (not sure how that's measured... ppm?) in relation to greenhouse gasses and general pollution and any proposed timeline for heavier restrictions either federally or in California. Any information available to educate motorized scooter consumers about these emissions requirements would also be appreciated.


I have found a Regulatory Announcment from EPA dated Dec 2003 that I believe contains the answer to your question.
"The U.S. Environmental Protection Agency (EPA) is adopting more stringent emission standards for new highway motorcycles. Under the current standards, which are over 20 years old, today's motorcycles produce more harmful emissions per mile than a car or even a large sport utility vehicle (SUV). These new standards will reduce the combined hydrocarbon and nitrogen oxide emissions in the exhaust by 50 percent as well as the harmful health effects of mobile source air toxics.... "
Also the document states that
"In this final rule, EPA is adopting new emission standards for exhaust and evaporative emissions from highway motorcycles. The standards are based on comparable requirements adopted in California. The final rule extends the California requirements nationwide two years after they initially take effect in California. "
Here is the table
Highway Motorcycle Exhaust Emission Standard
Class Engine Size (cc) Implementation Date HC g/Km HC+NOx g/km CO g/km

  • Class I Less than 170 2006 1.0 - 12
  • Class II 170-279 2006 1.0 - 12
  • Class III 280 & above 2006 - 1.4 12
  • Class III 280 & above 2010 - 0.8 12

You can access the whole document at
I din't provide the California data because as you can see from the comment they are the same.

Request for Answer Clarification:

Thanks for posting! That's a step in the right direction, but I'm not looking for motorcycle engine emission info. There's a different category for small engines. That's what I need. These small engines are used in lawnmowers, leaf blowers, gas scooters, etc. They are 2stroke or 4stroke and I believe they are designated as 50cc or less in size. The emission requirements are different in California from Federal requirements and I need both. I did some poking around and I believe the greenhouse gasses for which I need emission standards info on are primarily; Carbon Dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O), and secondarily; Hydrofluorocarbons: HFC-23, HFC-125, HFC-134a, HFC-143a, HFC-236fa, and Perfluorocarbons: CF4, C2F6, and Sulfur Hexafluoride. As long as I have the info on the primary gasses... that's fine. If you can find the secondary... more power to ya.
I'm also need a couple of other things;
  • Any news related to if and when California or the Federal government may increase these emissions standards, i.e. I believe the Federal gov may have a timeline to match California standards.
  • Any summarized information presented in a non-technical format for consumers.

Clarification of Answer :

I found the Phase 2 Emission Standards for New Nonroad Spark-Ignition Handheld Engines at or Below 19 Kilowatts and Minor Amendments to Emission Requirements Applicable to Small Spark-Ignition Engines and Marine Spark-Ignition Engines; Final Rule.
You can find it at
I will copy here a summary of the tables,
  • Class III less that 20cc
  • Class IV 20cc to 50cc
  • Class V more than 50 cc
  • Class I-A less than 66 cc
  • Class I-B more than 66 cc less than 100 cc
Engine class HC+NOX Standards (g/kW-hr) by model year
2002 2003 2004 2005 2006 2007 and later
Class III 238 175 113 50 50 50
Class IV 196 148 99 50 50 50
Class V 143 119 96 72
Engine class CO standard (g/kWhr) Effective model year
Class III 805 2002
Class IV 805 2002
Class V 603 2004
Engine class HC+NOX (g/kW-hr) NMHC+NOX CO (g/kW-hr) Effective year
Class I A 50 * 610 2001
Class I B 40 37 610 2001

I found the CARB standards summarized at
The table is the following
TABLE 7-4 Existing CARB Small-Engine Exhaust Emissions Standards, Adopted in 2004 (also referred to as Tier 3)

Engine Displacement HC + NOx, g/kW-h CO, g/kW-h
2005 2006 2007 2008+ 2005+
<50 cc 50 50 50 50 536
50-80 cc 72 72 72 72 536
80-225 cc 16.1 16.1 10.0 10.0 549
>225 cc 12.1 12.1 12.1 8.0 549
Source: CARB 2004f.

Request for Answer Clarification

Those are good figures. I was hoping for greenhouse gas measurements as well, but I've done some more poking around myself and it looks like greenhouse gas measurements aren't taken on motorized scooters. So, dead end there.
The Federal EPA numbers you've found are for handheld motors. Can you confirm they apply to motorized scooter motors which I believe fall under the category of non-handheld motors. If there are different emissions standards for "non-handheld" motorized scooter motors I'll need those... that's what I'm after.
Finally, I'm looking for any news related to if and when California or the Federal government may increase these emissions standards, i.e. I believe the Federal gov may have a timeline to match California standards.

Clarification of Answer

You can find the categorization of EPA for NonRoad Engines, Equipment and Vehicles at
The list is

  • Compression-Ignition Engines (farm, construction, mining, etc.)
  • Small Spark-Ignition Engines (lawn mowers, leaf blowers, chainsaws, etc.)
  • Large Spark-Ignition Engines (forklifts, generators, etc.)
  • Marine Diesel Engines (commercial ships, recreational diesel etc.)
  • Marine Spark-Ignition Engines (boats, personal watercraft, etc.)
  • Recreational Vehicles (snowmobiles, dirt bikes, all-terrain vehicles, etc.)
  • Locomotives
  • Aviation (aircraft, ground support equipment, etc.)

The data I gave you were for the Small Spark-Ignition Engines, you can find the whole list of regulation for Small Ignition Engines at
Here you will also find a document "Minor Amendments to Emission Requirements Applicable to Small Nonroad Spark-Ignition Engines and Marine Spark-Ignition Engines"
In that document there is a section that is titled The weight limit in the definition of "handheld" in the small SI rule
I quote from that
"Background: Handheld equipment has historically used lightweight two stroke engines which have much higher emissions than the heavier four stroke engines. While the Small SI rule regulates the emissions from both "handheld" and "nonhandheld" engines, it applies less stringent standards to "handheld" engines than to "nonhandheld" engines. To limit the use of two stroke engines to equipment that truly must be "handheld," the Small SI rule provides for equipment weight limits above which a piece of equipment is considered non-handheld and must use an engine which meets the more stringent nonhandheld engine standards.
Recently, a manufacturer of handheld equipment pointed out that the current weight limits on handheld equipment prevent the use of lightweight four stroke engines that are intended for handheld equipment and are much cleaner than conventional two stroke engines.
Final Rule: We are not changing the weight limits, but in cases where a piece of equipment exceeds the weight limit, the engine will still be eligible for the handheld standards, if the excess weight is directly attributable to the use of a four stroke engine or other clean technology."
And in the document
I have found
"5. Handheld Engine Qualifications Small SI engines are categorized as either handheld or nonhandheld, depending on the use of the equipment in which the engine is installed.
A handheld engine must meet at least one of the following four conditions:
  • The engine must be used in a piece of equipment that is carried by the operator throughout the performance of the intended function(s).
  • The engine must be used in a piece of equipment that must operate multipositionally, such as upside-down and/or sideways, to meet its intended function(s).
  • The engine must be used in a one-person auger for which the combined engine and equipment dry weight is under 20 kilograms (kg).
  • The engine must be used in a piece of equipment, other than an augur, for which the combined engine and equipment dry weight is under 14 kg, no more than two wheels are present, and at least one of the following attributes is also present:
    - The operator must alternately provide support or carry the equipment throughout the performance of its intended function(s).
    - The operator must provide support or attitudinal control for the equipment throughout the performance of its intended function(s).
    - The engine is used in a hand portable generator or pump."
    As you can see from there is a Phase 3 proposal for emission standards. I looked at the docket as they say but could not find any definitive date by which they have to approve it.