Mongoose Right Bike Gears shifting up magically On the right, or back gears of my mongoose bicycle, the gears are not clicking as they should on the right side. Its stuck in 6th or 7th gear and it has a grip-shift that works fine on the left side. When I try to shift down I can hold it down and it will stay in gear but when I let go it flies back up to 6th gear. How can I fix this?
It sounds like you have a broken or worn shifter. Grip shifters have small plastic teeth inside them. The teeth loosely mesh so that it will move when twisted but tight enough to maintain the selected gear. These shifters are still common and relatively inexpensive generally around $10 US.