When I hold the engine at its highest RPMS ( full throtle ) for just a little to long, it randomly revs really high and goes back to normal and at the same time makes a metal vs. metal squealing noise. I know it has to do with the small cog on in the crank case. I am continually replacing woodruff keys and the ones I am putting in are to small cause its the closest size home depot has. Anyway yesterday I was riding and they key came out again and I tried to remove the small cog to put a replacement in but now it wont come out. I've tried pulling it pretty hard with some pliers too. The engine is still functional, but it does that high rpm reving thing.