Small Engine Troubleshooting Problems? Ask a Mechanic Now.
This is single speed transmission, and the shift lever just moves transmission lever from side to side for F/R. Go direct to the shift lever on the transmission, and see if you can shift the transmission into forward with no problem. If you can, adjust the shift linkage to get longer throw for forward . Shift linkage may have slipped.
Did you find the linkage to be the problem?