The specially adapted fleet of bikes will be able to rush test samples to laboratories from remote areas, where patients can often wait nine days or more for results.
The UN's World Food Programme (WFP) said the motorbikes should cut transport delays to a day.
Experts say faster test results could help slow the spread of the epidemic, which has so far claimed more than 5,400 lives, according to the UN.
"The samples coming from 53 districts in the three worst-affected countries - Sierra Leone, Guinea and Liberia - will be able to be taken to the closest laboratory in less than 24 hours," said WFP spokeswoman Elisabeth Byrs.
The announcement comes as a new airlift by the agency, the fifth since September, landed in the Liberian capital Monrovia carrying water kits and generators.
The WFP estimates that 1.7 million people in the three countries are threatened by hunger, 200,000 of them directly because of the Ebola outbreak.