Front variator for the Honda Lead 90 (with pin): a drive pulley with rollers. It changes the transmission ratio smoothly as engine speed rises. Manufacturer: DONCXIN.
Replace it if the rollers and guides are worn, acceleration is sluggish, or it vibrates and overheats. The condition of the variator also affects the belt, so check the belt too.
After replacing it, check the assembly at idle and while riding: there should be no unusual noises, leaks, or play.
