7 Gear Grip Shifter Pulls out of Low Gears

[rowerca]

My kid's Shimano grip shifter won't stay in anything but 7th gear. If we shift into a lower gear, it seems like tension pulls it right back to 7. I've loosened the barrel adjusters as much as possible. Can it be that the cable is just too short? Any thoughts? Thanks in advance.

[Paulius]

Have you checked the cable tension? Shift it into the lowest gear, on the rear derailleur unscrew the bolt that holds the cable, give the cable some tension and tighten the screw. Then mess around with the adjusters.
http://bicycletutor.com/adjust-rear-derailleur/
this link should be really helpful

Cheers