I am tuning up a Craftsman with a 6.5 Tecumseh engine. I am doing it for a friend that had run it for 3 years with no service. He said it was running sluggish. I cleaned the carb, replaced the plug, air filter, cracked breather tube, and replaced a broken drive control cable. When I attempt to start it, the starter will operate normally when pulled slow, but it will jerk (somtimes pretty violently) back in when pulled quick. Small fine wisps of white smoke come from the muffler almost immediatly when I pull the rope. It is very small amounts, but will last about 1-2 minutes after I pull the rope without it starting. I did not start the mower when I got it because it was low on oil, which had also been in the engine for at least 3 years, so I am not sure as to it's running condition other then what my friend described prior to my service. I did tip the mower up to service it's drive control after removing the gas tank and draining the oil. I have not seen smoking of the muffler without at least the engine sputtering so I'm not sure if it's just some oil that has gotten into the muffler or cumbustion chamber from being tipped. Any ideas or tips would be appreciated.

check the flywheel key, I bet its out of whack just enough to throw the timing off

I agree with pyro, it could have a partially sheared flywheel key. Also make sure there is a blade installed and that it's tight, as this can also cause the starter rope to jerk back from your hand.

It starts great now...I didn't put the blade back on because I didn't put any of the drive and belt covers on. I was thinking at work today and remembered that when I was about 12 I didn't put the blade on and the mower was hard to start. I mentioned it to a buddy and he thought I was crazy. Why does that happen? I noticed that the air filter had a lot of gas in it when I first took it apart. Is there any reason why that would happen? This model seems to have a poor design for the air filter compartment. For sake of making the engine look more areodynamic, the filter seams up with the top cover of the engine, any water that may get on the top runs right down into the filter. It's the only one I've ever seen that does that. I was thinking that some gas may have run out of the tank when my friend tried to fix the drive cable and into the filter compartment.

I didn't put the blade back on because I didn't put any of the drive and belt covers on. I was thinking at work today and remembered that when I was about 12 I didn't put the blade on and the mower was hard to start. I mentioned it to a buddy and he thought I was crazy. Why does that happen?

Most small engine ignitions are set slightly advanced, the blade acts as a counter balance and the inertia from the blade spinning keeps the engine rotating when the the spark plugs ignites the fuel/air mixture. Without the blade you don't have enough inertia to keep the engine rotating so when the plug fires, the engine tries to spin backwards. If you pull the rope hard and fast enough you can get the engine to start, but sometimes you can also shear the flywheel key. :thumbsup:

Thanks for the information. I'll let my friend know I wasn't crazy....makes me feel better.