Council bosses made the admission that the purpose-built track at Doncaster Dome, Lakeside, went £108,000 over budget.
The shortfall had to be made up from extra council funding, documents on the local authority records page shows.
Council finance chiefs made the decision to source the rest of the money internally, because it could have delayed the opening planned for the UCI Road World Championships, which came through Doncaster last year.
The council said no further external funding was available.
The track had been built ahead of the cycling championships with the women’s junior race and the men’s under-23 event starting from the Lakeside facility.
Reports show the overspend resulted from the construction of a cobbled hill section of the cycle track.
The one kilometre-long, six-metre-wide track has proved popular and aims to provide a safe off-road space for children to learn how to ride a bike and for more intermediate and expert riders.
The track - costing £1.6 million - was funded by British Cycling, Sport England and the Department for Digital, Culture, Media and Sport, with a contribution from the council.
Andy Maddox, Doncaster Council leisure services business development manager, said: “The project team made every effort to reduce and reutilise funds where possible.
“However, spend over and above the budget was still necessary to complete construction.
“There were variations across a number of elements of work during construction.
“The most notable was in relation to ‘Earthworks’ completed – this was predominantly in relation to the ‘cobbled hill section’ of the circuit, which required an additional £104,000
“As the overall design for the circuit was agreed with Sport England and British Cycling, by not committing to the overspend and completing construction in line with the agreed designs, there was a risk of withdrawal of external funding, preventing construction being completed.
“This would have also had a significant impact on delivery of the UCI Road World Championships.”