Cleaned, changed oil, now rope jerks back

[commcheck]

I have 917.387321 craftsman push mower (1998). Tonight I pulled the shroud off, cleaned the engine (wiped it down) of dirt/grease, etc. I put shroud back on, drained and put in new oil and replaced the air filter. Now, when I pull rope, it jerks back out of my hand about half-way out. If I pull rope slow, I can fairly easily pull rope way out, but pulling fast/hard on it and the rope wants to jerk back. If I am at all successful at getting engine started, it sounds like it's not quite running at full power, and occasionally a minor backfire. When I release the brake handle, the engine stops NOW, rather than the usual 1 or 2 seconds it normally takes. If I remove the shroud, and put my hand on the flywheel (which has the magnet on one side and a balance weight embedding across from it), I can easily rotate it around...no resistance. I don't understand why all the sudden this is occurring. I had started the engine just minutes prior to warm the engine before changing the oil. I've never had any issues with this mower until now all of the sudden.

 

[BKBrown]

I am not familiar with this particular mower or engine, but it sounds like you may have dislodged or moved something when you had the shroud off during the cleaning, Is there a cylinder pressure release on this engine that might have a spring either moved or dirt under it preventing it from closing ?
Is the shroud holding a part that needs to move freely ? I doubt the oil change caused any problems.
Good Luck finding your problem.

 

[jeff]

I am thinking about the engine brake not releasing when the handle bail is pulled back for starting.

 

[commcheck]

I continued this morning troubleshooting the lawnmower. I first pulled out the spark plug and pulled the rope...it pulled very freely, but no oil or anything came out of the spark plug hole. I put the spark plug back in, pulled rope, back to same symptoms...about half-way out with the rope and it wanted to jerk back on me. I removed the shroud, looked everything over again (for 3rd time). Brake seemed OK and was working normally, etc. Then, thinking I may have overfilled the oil, I drained about 20% of it, but no help. I started thinking more into the flywheel and whether it could have anything to do with the key (but I haven't hit anything with it...I ran it a few weeks ago just to make sure it started after winter storeage). Thinking at this point I was going to need to drain the oil to keep from it spouting out while monkeying with the flywheel, I got to thinking about the blade of which I had removed to take with me to work on Monday to sharpen on our grinding wheel. I had run the mower before WITHOUT the blade, but I don't recall having had this kind of trouble. I decided to put the blade back on, and WALLAH...the rope pulled normally. I primed the engine, pulled the rope a few times and it started up. I shut it off, restarted it again, wallah. Weird. I guess the blade needed to be on, but, I swear I've run it before without the blade. In any case. I've learned a little bit more about my mower, and more about troubleshooting in general (I'm don't consider myself a mechanic but I'm always up to a challenge). Thanks for your inputs...and maybe someone else will read this one day with the same symptoms and have a "duh" moment too.

 

[RobertBrown]

I continued this morning troubleshooting the lawnmower. I first pulled out the spark plug and pulled the rope...it pulled very freely, but no oil or anything came out of the spark plug hole. I put the spark plug back in, pulled rope, back to same symptoms...about half-way out with the rope and it wanted to jerk back on me. I removed the shroud, looked everything over again (for 3rd time). Brake seemed OK and was working normally, etc. Then, thinking I may have overfilled the oil, I drained about 20% of it, but no help. I started thinking more into the flywheel and whether it could have anything to do with the key (but I haven't hit anything with it...I ran it a few weeks ago just to make sure it started after winter storeage). Thinking at this point I was going to need to drain the oil to keep from it spouting out while monkeying with the flywheel, I got to thinking about the blade of which I had removed to take with me to work on Monday to sharpen on our grinding wheel. I had run the mower before WITHOUT the blade, but I don't recall having had this kind of trouble. I decided to put the blade back on, and WALLAH...the rope pulled normally. I primed the engine, pulled the rope a few times and it started up. I shut it off, restarted it again, wallah. Weird. I guess the blade needed to be on, but, I swear I've run it before without the blade. In any case. I've learned a little bit more about my mower, and more about troubleshooting in general (I'm don't consider myself a mechanic but I'm always up to a challenge). Thanks for your inputs...and maybe someone else will read this one day with the same symptoms and have a "duh" moment too.

Thanks for following up with the post indictaing the resolution to your problem. That is useful information, inertia can be a a valuable tool.

 

[BKBrown]

Thanks for the follow up - I don't believe you said anything about the blade being removed. The blade will act as a flywheel weight and keep the engine turning in that direction, yes the lack of that spinning weight could cause your problem. Glad you figured it out ! :thumbsup:
When you grind the blade be careful not to get it too hot, it will remove the temper (hardness).

 

[wildbill]

The rope jerking out of your hand when cranking is most likely caused from the key that keeps the flywheel in time with the piston-valves has sheared. Remove the shroud, remove the large nut in the center of the flywheel, and then remove the flywheel. You may need to get a shop to pull the flywheel, sometimes it comes off with ease, sometimes not. A repair shop will do it in snap with a puller. There is a groove machined in the crankshaft that matches a groove in the flywheel bore. Its much better to have a sheared key than a broken crankshaft.................. the key costs maybe a buck-50. good luck

 

[rer]

Get a loaner tool from the auto part store. they have it all. I use Advance Auto Parts

 

[Rod]

I have an identical problem that I noticed yesterday for the first time on a Poulan that I bought a couple years ago, and it has the blade on. I'm thinking wildbill has the answer for me.
The last time I used it, it ran extremely irregularly and roughly - like it was going to die. Almost felt as if the fuel was getting dumped in without appropriate regulation. As you can tell, I'm no lawnmower mechanic. I also noted at that time when I restarted it after emptying the bag, that it would backfire and sometimes sparks would come out. Anyway, I finished mowing, embarrassed whenever someone came by looking at me wondering why I was using a mower that fiunctioned like that. Now the next time I try to use the mower, I get the behavior described by the poster aabove. It pulls smoothly about halfway and then it jerks backwards in a way that is actually very dramatic and hurts my shoulder. It didn't start after a few pulls and it is too risky to my body to keep pulling the pull cord.
So is this in fact probably a broken key between the flywheel and pistons (or whatever). And secondly, is this probably why this mower has been running so bad. Or is it two separate problems.
Thanks.
Rod

 

[wjjones]

I continued this morning troubleshooting the lawnmower. I first pulled out the spark plug and pulled the rope...it pulled very freely, but no oil or anything came out of the spark plug hole. I put the spark plug back in, pulled rope, back to same symptoms...about half-way out with the rope and it wanted to jerk back on me. I removed the shroud, looked everything over again (for 3rd time). Brake seemed OK and was working normally, etc. Then, thinking I may have overfilled the oil, I drained about 20% of it, but no help. I started thinking more into the flywheel and whether it could have anything to do with the key (but I haven't hit anything with it...I ran it a few weeks ago just to make sure it started after winter storeage). Thinking at this point I was going to need to drain the oil to keep from it spouting out while monkeying with the flywheel, I got to thinking about the blade of which I had removed to take with me to work on Monday to sharpen on our grinding wheel. I had run the mower before WITHOUT the blade, but I don't recall having had this kind of trouble. I decided to put the blade back on, and WALLAH...the rope pulled normally. I primed the engine, pulled the rope a few times and it started up. I shut it off, restarted it again, wallah. Weird. I guess the blade needed to be on, but, I swear I've run it before without the blade. In any case. I've learned a little bit more about my mower, and more about troubleshooting in general (I'm don't consider myself a mechanic but I'm always up to a challenge). Thanks for your inputs...and maybe someone else will read this one day with the same symptoms and have a "duh" moment too.

I have Duh moments all the time... Thankyou for the info...:smile: