stumped

bdunegan · Aug 27, 2015

I have a craftsman LT2000 with a 21hp single Briggs engine that has me stumped. It has a bad vibration when blades are engaged. It is so bad whole motor shakes. I have changed blades, no change. Run without blades, no change even swapped a perfect running deck off another mower, no change. Have used a straight edge alongside of engine pulley while running. Pulley runs true with no wobble. Motor runs great and without deck engaged it is smooth but when deck engages it shakes real bad. Motor mounting bolts are tight and mounting surface is not cracked anywhere. Motor has no vibration at all while running free but when deck (no matter which deck, blades or no blades) engages, it nearly shakes you off mower. Not too bad while in motion mowing but when you stop and sit still with deck engaged, it shakes. Any ideas. Is there some kind of balance weights on motor somewhere that might have come loose? Motor runs and idles very smooth with no smoke at all and no oil use. No rattles of any kind! Help!!!

Jay Phillips · Aug 27, 2015

Since you have also swapped decks and the problem does not go away, you've somewhat narrowed it down.

Have you thoroughly inspected the belt for damage or defects? I had a similar problem with a NEW belt. There was a lump on the side of the belt in one spot. It would shake like crazy!

If that's not the culprit, inspect the idler pulley(s) that tension the belt. (I'm not familiar with your model mower, so I don't know if they're on the deck or the mower.)

Good luck,
Jay

john *.?-!.* cub owner · Aug 27, 2015

Not familiar with an LT2000, but I would check for a rock or something similar wedged in the grooves of the motor pulley, or idler pulley if the idlers stayed with the tractor when you changed decks. Only one guess why I would think of that being the problem, and it nearly drove me nuts, except I did not have an extra deck to try.

bdunegan · Aug 27, 2015

The idler pulleys that tension deck belt are on deck. And since I changed decks, I don't think that is it. Also when I changed decks, I used the belt that was on the deck I changed to, and I know it is a good belt, so that ain't it. I thought maybe one of the tension pulleys on the drive belt might be bad causing extra strain when the deck is engaged, but I checked all pulleys and they are fine with no wobble or bent spots whatsoever. Mower drives good and smooth and runs great just driving it around, but when you engage deck, hang on! Thanks for the replies, they were great ideas! Any more? Lol

T.R.K. · Aug 27, 2015

Like the other guy said, check the belt for wide spots or thin spots. And check for anything wedged in the pulley.

That said, We had some Husqvarnas about 3-4-5 years ago that had a problem with the engine pulley. The PTO flange would be usually out less than 1/16" but was enough to be visible when the engine spun down to a stop. I just tell you that because Husqvarna probably made your Craftsman.
A new pulley was the fix in that case.

bdunegan · Aug 27, 2015

That is my next change. I have a new pulley just like the one on it, so I will change it and see what happens. Thanks!

jeffcat · Aug 27, 2015

Just a little off but you will understand. There is nothing like someone not loosening the tension bolts on an electric motor and moving it a little to change the belt. NOOOOOO they take a big honkin screw driver and pry it on and off. Guess what happens to the pulley????

spacecadet9 · Aug 28, 2015

(quoted from post at 21:05:18 08/27/15) because Husqvarna probably made your Craftsman.

I have a LT2000 that's a MTD/Cub Cadet/Troy Bilt.

ztrmower · Aug 29, 2015

is this a manual engage unit or electric clutch unit? have seen keys on drive pulley wedge wrong will shake s???t out things when try deck engage

bdunegan · Aug 29, 2015

Update! Changed engine pulley today and still no change. Checked drive belt (not that it has anything g to do with problem cause drives fine). Belt is good and checked pulleys again. Removed deck belt although I changed it when I changed decks and checked it. It is fine. I have checked everything I know of with no good results. It still shakes when deck engages. It is manual engage and not electric clutch if that helps anyone with ideas. Like I said, it drives smooth with no jerking at all and motor is smooth with no movement but when deck engages, it will nearly shake you off the seat.

tractorguy2 · Aug 29, 2015

snapper mowers will sometimes break the spot welds on the crank pulley. Belt tension will then cause the pulley to spread and make the deck shake.

Jay Phillips · Aug 30, 2015

I believe you are missing something.

Since you have swapped decks, and the problem didn't go away we know it's NOT the deck or the belt tensioner.

So, it MUST be the deck belt, or it's drive pulley. And to shake as bad as you've described I can't imagine what is causing the problem.

It's there....you just have to look a little harder.

Jay

kevinstuff · Sep 1, 2015

Loose flywheel on engine or bad balancer on engine or sheared key on motor pulley?

Jay Phillips · Sep 2, 2015

Are there any updates?

Just curious if you found the problem.

Jay

bdunegan · Sep 2, 2015

I have now changed decks with one off a perfect working mower, changed engine pulley with a new one. New deck belt, removed all mower related pulleys and checked bearings and flanges for cracks. Checked keyway on shaft and key in new pulley, and still found nothing. Can't understand why engine runs perfectly smooth with no vibration, and tractor drives around just fine, but only vibrates when mower is engaged. One person suggested maybe loose flywheel, but if it was that loose, wouldn't it vibrate just setting still running. I am gonna recheck all linkage and mounting brackets on deck and make sure something there is not bent or something, but deck mows level, but I doubt that is the cause.

Jay Phillips · Sep 3, 2015

The problem you're having....is it a "vibration", or is the engine missing and not running smooth?

If it's the engine not running properly that's causing the vibration, the problem is with the engine. Possibly something in the fuel, timing (shearer key), etc. There are only a few things that would cause the engine to run rough only when under a load.

Jay

bdunegan · Sep 3, 2015

I have thought of that too! engine is running smooth until put under load. Carb is clean and new fuel line and filter. motor doesn't seem to be starving for gas.(gravity feed, no fuel pump). If flywheel key was sheared any at all wouldn't motor be hard to crank over and backfire because timing is off and not run smooth at all anytime?

Jay Phillips · Sep 3, 2015

Just to rule it out, completely flush the fuel system, and replace with NEW gasoline. Preferably from a known CLEAN container.

I would also think that if the key were sheared that it would run rough all the time.

It would be hard cranking if in an "advanced" position, but it it has sheared and currently in the "retarded" position it would crank over fine.

bdunegan · Sep 3, 2015

Thanks for the info. Never thought that key could be sheared in retarded timing position, therefore would still be easy cranking. I said motor idles and runs smooth, but the more I listen to it and ponder over it, it don't sound exactly quite right to me. So as per your advice, flushing fuel and checking flywheel is my next step! if it is missing, then put under load, it would definitely shake!

Jay Phillips · Sep 4, 2015

Since it's the easiest.....try the fuel first.

Make sure to empty the bowl on the carburetor, too.

Jay

bdunegan · Sep 5, 2015

Flushed fuel system, drained and cleaned carb, drained tank, changed fuel filter, fresh gas, pulled flywheel, key right where it is supposed to be, and no luck. Still the same. While I was removing flywheel, I noticed motor didn't seem to have the compression I think it should. I have reset valves to spec once before. Could it possibly be a valve carboned up or maybe a blown head gasket leaking compression? Looks like I am pulling head to have a look. If gasket is blown, it must be blown in just the right spot because engine don't smoke at all and since it don't smoke, I wouldn't think a stuck or broke ring!

Jay Phillips · Sep 5, 2015

Anything other than fuel, I would think the engine would just be down on power.

Hmmmm....have you tried bypassing all of the safety switches, that kill the power. For example, seat switch, neutral switch, etc.

Maybe the ignition is being shut off intermittently by one of the switches that's either out of adjustment or beginning to fail. But, if this were the case, I would think there would be a lot of back-firing.

bdunegan · Sep 5, 2015

There has never been any backfire at all even going from slow idle to full throttle and back down. I would think if it was electrical, it would. If engine was down on power with low compression, it would be rings, but no smoke anywhere. I did notice that while running with breather off carb, I was getting a little gas spitting out of carb. Carb don't seem to be flooding tho while running. It throttles up just fine with no black smoke, but engine does seem to be missing. I don't thing coil and plug could be firing intermittently without it backfiring.i have checked push rods, and they aren't bent. I just can't think of anything else that could cause it to have low compression except valves or head gasket.

bdunegan · Sep 6, 2015

Update! Maybe I found the culprit. I decided it had to be valves or head gasket so I set in and took valve cover off and checked valves once again before anything else. I had just set them at beginning of season, so I didn't expect them, but rolling piston over to 1/4 past TDC, the intake valve was extremely tight and exhaust was still OK. To make a long story short, I reset valves once again to spec and made sure the center lock screw was good and tight, rolled motor over and it has great compression. Put valve cover back on and cranked it up. Runs good and smooth, and even mowed with it! What a big difference, I can actually stay on it now without my teeth chattering! Just goes to show that just because you did something to it not long ago, doesn't mean to assume it is still OK and not check it to be sure! Thanks everyone especially Jay for all the ideas and help!!!!

Jay Phillips · Sep 6, 2015

As soon as I read your reply about the fuel spitting out of the carb, I was pretty sure that had something to do with the valves.

Glad to hear that you figured it out.

A lot of the guessing from me and others early on, were thrown off by the description of the problem being a vibration and not a miss. That's why were were looking for things that could cause a vibration.

Lots of times it's something very simple causing us to lose our hair. LOL

Glad you're back to smooth mowing.

S/C BOB · Sep 25, 2015

one time I had a rider pick up a piece of stick and it wedged in one of the pulleys very odd but it did make things shake pretty good. Good luck

stumped

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