According to the TBR RC-31 racing carb kit, this is how you disable the California emmisions equipment.
If you own a California or 1991 model: 1) Cap all of the smog control related fittings on the side of the carburator that connects to the engine, using the plastic caps provided. Leave all breathers on the air intake side open, i.e., vented to atmosphere. Direct them away from air blast. 2) Disable the Air Suction Valve (ASV) as follows (this is the device that looks like a pump just above the crankcase on the left side of the bike): a) Plug hose running from the ASV to the airbox. b) Plug small hose running from the ASV to the cylinder head intake horns where it connects to a Y fitting just above the ASV c) Replace the brass hose barbs in the intake horns with 5mm bolts, reusing the aluminum crush washers removed from the hose barbs.
At the bottom of the page it has this friendly warning:
Please remember that this kit and the described modifications violate all State & Federal pollution laws as well as your Honda warranty. The kit and prescribed modifications are intended for closed course competition use only and are not in any way intended for street or public highway use.
This is a quite useful explanation from James Montebello
To do this painlessly, you need to understand what each hose does.
This isn't rocket science.
Each hose will serve one of three functions:
The first type can be plugged in all cases with no ill effects.
The third type should never be plugged, or the engine will run poorly or not at all.
The second type is an "it depends".
The ASV (air suction valve) is, in fact, the smog pump, and is that big ugly thing
on the side of the engine. It is powered by intake vacuum, and sucks air out of the
airbox and into the exhaust ports. The exhaust ports, the airbox port, and the vacuum port
all need to be plugged.
The other half of the smog system is the evaporative canister. This device is supposed
to trap vapors from hot fuel in the tank and the float bowls in a charcoal filter while
the engine is off. When the engine is running, Air is sucked in through the filter, along
with the trapped vapors, and into the engine. There are two vacuum powered valves that
determine when the engine is "on".
When the ACV (air control valve, or air vent control valve) is in the engine off position,
the float bowls are vented into the canister. When the ACV is in the engine on position,
the float bowls are vented to the atmosphere. When you remove the ACV, you need to
plug the vacuum line, and leave the float bowl vent open. If the float bowl vent is plugged,
the engine will die quickly after starting, if it starts at all, since there will be no atmospheric
pressure "pushing" the fuel out of the bowl.
The other valve is the PCV (purge control valve). It vents the canister to the intake
manifolds to burn the trapped vapors when the engine is on, and simply plugs these
when the engine is off. All of the lines here need to be plugged. If the intake manifold
ports are not plugged, there will be a vacuum leak, and the mixture will be very lean.
----- James Montebello -