BMX: Rio 2016 organisers have been forced to make alterations to the Olympic track, after BMX riders cited dangerous turns and jumps during the test event in Rio.

The two-day test event was reduced to one day after some of the world's top riders declined to race on Saturday, maintaining some of the jumps were too high.

Organisers tried to modify the track for Sunday after changes requested by the International Cycling Union, but both men and women wound up using the women's circuit as the men's course was deemed too risky.

Australian Olympic hopeful Bodi Turner rode both versions of the course and says there is still work to be done.

"We rode Friday afternoon when they opened it up. We thought it was a good opportunity to test out the sections that we didn't think were simple to race," Turner, 21, told AAP.

"For the girls' straight it was mainly just conditioning. The straights just weren't really smooth and I guess a little out of shape.

"They just had to straighten those up and they still need a little bit of work, but the biggest issue was our men's straight. It was a little bit gnarly."

Compatriot Lauren Reynolds, who made the semi-finals of the London Olympics, said overall the course was good.

"They've made the suitable changes to make a race happen for today so I think they've done very well there," she told AAP.

"I'm excited to race it. The majority of it is not going to change, there will be a few little things but there is still so much to benefit from being here today and racing, rather than opting to pull out which a lot of people have."

In a further blow afternoon rain washed out the event on Sunday, but organisers said they would further increase both the excitement and the safety of the course.

AAP