Cheng Jin Lai, 78, was hit and killed by an outbound 27-Bryant bus around 8:40 a.m. last Friday at Bryant and 11th streets.
Muni spokesman Paul Rose said the agency is still working with police to investigate the collision and that it is too early to confirm any details about the case.
However, because of reports that the bus was missing a rear right wheel guard when it struck Lai, Muni is now inspecting its entire fleet, Rose said.
The device in question, called an S-1 Gard, is installed on all buses "to reduce the chances of impact with the back right tire," Rose said.
He said, however, that the device is not required under Muni regulations.
The S-1 Gard is also included on bus fleets in San Jose, Los Angeles, Washington, D.C., and Baltimore.
The San Francisco Bicycle Coalition held an event Wednesday morning encouraging the city to improve safety measures for bicyclists in the wake of Lai's death.
Lai is the fourth bicyclist to be killed by a vehicle in San Francisco this year. All four deaths occurred in the city's South of Market neighborhood.