"They're a bit cunning, the guys on the motorbikes.
"They'll come in and have a scream up and down the field, might shoot through River Rd way or out by the bridge on Colombo Rd, and then they go away for a few minutes and come back.
"I think that's to avoid the police."
The resident said it was neither the time nor the place for the motorcyclists to be honing - "not near a kid's playground".
"It's been going on, off and on, for months. Sometimes it gets worse but it seems to have cooled off during the winter, but some weeks it's like every day.
"It's just a shame because the community really pitched in for the new playground and planted trees and did a lot of work there, and then [they] just come in and scream through on their motorbikes not wearing helmets.
"And they've driven through while these kids are playing in the playground, which is intimidating.
"My grandchildren get as angry as I do."
Police Sergeant Ian Osland said access to the park through river trails had been a major concern for Masterton East residents.
"It's been quite a long-running saga I guess," he said.
"We're trying to explore ways with council to limit the impact of motorcyclists along the river trail. There are so many access points that it's generally difficult to block it all off."
He said it was against a council bylaw to ride motorbikes along the river trails and riverbed.
Masterton District Council spokesman Sam Rossiter-Stead said motorcyclists had been illegally using the corridor between Oxford St and McJorrow Park to travel along the river banks.
"We are actively working with the community policing team and the staff at Mawley Holiday Park to identify offenders, and are investigating options for barriers that will stop motorbikes, but still allow pedestrian access," he said.
Council staff were meeting monthly with Ian Osland to identify ways to reduce crime through environmental design.
Examples could include better lighting, bollards or landscaping with large rocks.
Residents are encouraged to call police when they see motorbikes in the park.