Problems with my DB01R

[muratti]

Hey guys!

I have a problem with my DB01R and badly need some advice.
After now about 70 7min. runs i heard a strange chattering when speeding up quickly. A racing mate said he thinks it´s the rear belt getting loose. So i thought after 70 runs it´s not unnormal to change the belt. So i changed the rear belt, rear pulley and both Center pulleys. I built everything as per manual and still have this strange sound. It even got worse so that full throttle is almost not possible. I changed the diffs, they didn´t get loose.
Is it possible that i have to change the front belt and pulley too but it definitly sounds as if it comes from the rear end although i am not 100% sure as i can´t look at it while speeding up as there have to be the diff and center covers on to try out.
I simply don´t know what causes this chattering. It sound like a belt rolling over the pulley...
Please help!