I recently bought a 99 blaster with a bad bottom end. i replaced the bottom end with a used one. after rebuilding the top end and carb i get it running. now it idles fine, but when i shift out of neutral into 1st it pops forward and dies. when i swapped the clutch over the plates didnt look bad (you could still see the raised parts clearly on the friction plates. i adjusted the clutch so the clutch arm lined up with the mark on the case. any ideas on what i should look at next?