Starter Not Engaging Flywheel

time2mowJanuary 24, 2010


My Crafstman LT1000 tractor's starter will spin but will not engage flywheel. So, in response to the trouble I replaced the battery, then the solenoid and finally the stater. All parts OEM and new. The problem remains exactly the same. I would appreciate any suggestions.



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Check to see if you have installed the battery cables on the battery posts correctly. If the are are on the wrong posts, the starter will turn backwards causing it not to engage the flywheel.

    Bookmark   January 24, 2010 at 10:01AM
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The cables are correct. Another item to note is that I have bypassed the solenoid with a jumper from the positive terminal to the starter - same result - spins furiously without engaging flywheel. Thanks.

    Bookmark   January 24, 2010 at 10:43AM
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The only time i ever had your problem was when somebody had charged the battery backwards, and connecting the battery the correct way, caused your problem!
At least, try connecting it up with the positive to ground, and the negative to the starter post. Do this with the cable to ground being connected last.
A friend, who had no knowlege of auto mechanics, bought a battery trickle charger and connected it to his battery, with the clips on the wrong posts. since the battery was not very good, and probably "stone" dead. It recharged the battery with the negative current flowing the wrong way--or whatever. Me connecting it up the right way, made the starter spin backwards, so the little gear, which depends on centrifical force to raise it up, didn't--hence no spin of flywheel.
soon as i reversed the cables on the battery, it worked quite well!

    Bookmark   January 24, 2010 at 12:24PM
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Rusty,never would have thought of the battery being hooked up backwards. If that doesn't fix it,he needs to take the starter back-off and connect it to 12 V and check why gear is not raising up.

    Bookmark   January 24, 2010 at 12:38PM
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You didn't say what engine you have. If the battery checks out, post the complete model#s and part #s used. Also, have you inspected the ring gear itself? Every year I replace 1-2 Briggs 28s w/ the plastic ring gear.

    Bookmark   January 25, 2010 at 12:06AM
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Yah-but! Note: The starter gear is not moving up on the starter shaft! When the starter shaft is turning in the correct direction, centrifugal force applying itself to the starter gear weight that is molded into it, makes the gear move up on the shaft. When it meets the top of the shaft, it won't go up any further, so the force is applied to turning of the flywheel. If the starter is turning in the wrong direction, caused by reversing the connections, the gear is trying to move downwards on the threads of the assembly, but since it is already at the bottom of its allowable movement, it just stays down at the bottom, and turns fruitlessly, with no revolutions of the crankshaft.
Best way to illustrate this is to remove the starter, lay it on the floor, or clamp it in a vise. hook up the battery cables to it--first the correct way, and watch it turn and see the operation of the little starter gear. It will spin up to the top of the shaft. Then, reverse the connections and try it--you will see the gear move to the bottom of the shaft and stay there, which negates the correct operation of the starter, because the gear can never move up to meet the starter ring gear on the flywheel. By the way--if the little plastic gear is chewed up, best to replace it.

    Bookmark   January 25, 2010 at 11:10AM
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PLEASE DO NOT reverse the cables on the battery while everything else electrical is still connected. If I wanted to test rusty's advice/suggestion, I would remove the cable from the solenoid (that connects between the solenoid and the starter) and use the end of that cable to connect a separate battery to the starter using booster cables. Or, disconnect the tractor battery cables and use the tractor battery as the separate battery (this way you will not harm any diodes in the tractor harness). Normally, if the battery is charged with the correct polarity, and the cables are connected to the battery correctly, giving power to the starter cable will spin the starter in the right direction and raise the bendix to mesh with the flywheel (repeating rusty). So, it would be more accurate if you tested the starter using a battery from another vehicle (your car maybe) with a set of jumper cables. This way, if the starter spins, and the bendix rises up and meshes to the flywheel and the engine cranks. There is a polarity problem in the tractor battery. If you use the jumper cable trick, after connecting to the donor battery, connect the jumper negative cable to the frame of tractor (bare metal) and the positive jumper cable to the free end of the starter cable. It will spark, so don't be "startled". If the starter now cranks the engine, you will need to thoroughly go over your tractor battery cable and posts connection to see what the issue is. If the tractor battery appears to be connected correctly (negative to frame or chassis) but the starter turns opposite from the way it should, the battery has been charged backward (this would have required that the batter was completely discharged before being charged in reverse). Oh, it's possible that any diodes might already be fried, but that can be dealt with after you get this issue handled.

    Bookmark   January 25, 2010 at 1:30PM
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When looking down on the starter gear, it should turn counter clockwise when power is applied.

Walt Conner

    Bookmark   January 25, 2010 at 5:14PM
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Has any of the advise helped you solve your cranking problem or do you still have problems?

    Bookmark   January 27, 2010 at 9:21PM
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hankll((7) Tennessee)

I think hooking the battery in reverse to get the test for the starter would be ill advised. Take the starter off and test it on the work bench. Have you visually observed the actual gear part of the starter while cranking it, or is it under it's gear protection hood? This could be a stripped gear. And I'm sure that if you take it off, and take it the local lawnmower shop, they'd test it for you, and Autozone or other parts stores generally will test anything like that for free. It is the safest thing to do. Then all you need to do if it needs a new Bendix, is get it replaced, or replace the starter. There are several Briggs starters on EPay right now.

    Bookmark   January 28, 2010 at 8:23AM
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"I think hooking the battery in reverse to get the test for the starter would be ill advised. "

Simply reversing the battery cables is certain to result in either a blown fuse OR a burned out diode in the charging system.

Walt Conner

    Bookmark   January 28, 2010 at 4:37PM
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Well, that guy probably went to Haiti to help them down there. He can answer us when he gets back, and gets his head back on straight! RJ

    Bookmark   January 30, 2010 at 12:07PM
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Late to the the dance here. Tom Plum's post is the most likely scenario. To OP, rotate the fly wheel 90 degrees and try to start. Just like you do with a car with a bad ring gear. This is generic info, I have never even seen the engine or machine you have. I stick to 40 yr stuff that even worn out is of better build quality than the newer stuff. Plastic ring gears ? The 11 hp B+S flathead in my 77 Inty has a plastic starter gear that only lasts about 4 yrs. At least it is easy to change.

    Bookmark   January 31, 2010 at 9:57AM
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I have replaced plastic FLYWHEEL starter gears several times. And, the pinion gear on the starter many times.
And, if the little pinion gear won't raise up to engage the flywheel RING gear, no matter how you position the flywheel/ ring gear--it is not going to turn the crankshaft to start the engine! WHOOSH!

    Bookmark   February 1, 2010 at 12:07PM
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I am getting same problem gear on starter doesn't rise up to meet the flywheel. read that some people have changed battery, solenoid and starter with no results. problem still present after that. It is frustrating. But now I am building confidence to say it is some kind of wiring/connection problem. some connection is developing enough resistance and starter is not getting enough power. I am going to check all my wiring on mine. Not sure when i would be able to get time to do it. But if you have found anything and fixed it let me know please.

    Bookmark   July 27, 2010 at 10:49AM
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Here are some facts:
The starter is a DC motor.
DC motors rotate or spin according to the polarity of the current sent to them.
If you reverse the polarity of a DC motor, the motor will rotate in the opposite direction.
There are no connections on these tractors that can reverse the direction of the starter EXCEPT the battery cables.

Batteries are sold in "right hand" and "left hand" versions. The difference is in the location of the battery positive post in relation to the rest of the battery case.
This means that occasionally, somebody will buy the wrong battery, or be sold the wrong battery, but they will hook up the battery cables according to how they took them off (which will now be backward polarity).
When this happens, the first and most obvious problem the person will notice is "the starter runs backward and the drive gear stays down".

A DEAD battery (completely discharged) can be "charged backward", and doing so will effectively reverse the polarity of the battery. Engaging the starter with a battery that has been charged backward will produce the same symptoms that occur when a battery is connected in reversed polarity.

If you HAVE NOT replaced the battery, or charged the battery recently.............and suddenly the starter drive gear will not rise up to engage the flywheel, the starter drive is either stuck down, stripped out inside, or both.

It is possible for the starter drive to be a little bit "sticky" and cause it not to rise up if the battery is too weak to spin it up suddenly. If this were the case, the starter would spin in the normal direction of rotation, but slower than normal, and you might think it is a problem in the starter drive when it is really due to a weak battery.
If you have tried jump starting the tractor, or charging the battery, but get the same results......replace the starter drive gear assembly.

    Bookmark   July 27, 2010 at 12:01PM
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Thanks, Mownie: You have put what i said into the proper context!
A guy asked me to stop and show him why his starter shaft spun well, but the bendix gear would not rise up to engage the flywheel. So, i asked him if the battery was charged up enough. He said he had attached the charger cables, and charged it well. Said the battery was really dead, but it did come back up.
His tractor was quite old and neglected, an ancient Craftsman lawn tractor, in bad shape. So, i had him turn the ignition key, and there i saw his problem--Bendix gear turning wrong way. Now, he had connected and charged the battery, not me. This guy is the type who can never hold a job for very long, which precludes him from being handy with mechanical and electrical things. So, i changed the battery connections, and it started right away!
Mownie has come to my rescue, with his clear, simple advice and knowlege of what i have been saying all along!
by: Rustyj
P.S. It is great that some folks are engineering folk who know the big words to say, in this situation, but a back yard lawn mower fixer has to work by his hands, and brains, the experience comes later!
This same guy got a newer machine, and asked me why it was scalping his grass. I looked underneath and he had unscrewed the hangers on each side until the deck was sliding on the ground! I told him to tighten them back up to original position, and then turn the big black knob, to adjust the height! "Oh, is that what that thing is for?"
MMMMMMMMMMMMMMMMMMMMMMM! Reminds me of the box of rocks!

    Bookmark   July 27, 2010 at 1:07PM
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