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B&S Starter Gear shreds

lilmatty's Avatar
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04-11-06, 04:20 PM   #1  
B&S Starter Gear shreds

I've got a B&S model 42A707 motor. The starter motor gear that goes into the flywheel to crank the engine stripped on me. Half the teeth were sheared off. I replaced it with a kit and ran in bor about 2 hours when it did the same exact thing.

Before I do anything I thought I'd try to find out why this happened and if I can prevent it.

Any thoughts?


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v8driver's Avatar

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04-11-06, 05:29 PM   #2  
Oem or no-name brand? Make sure the starter is good and tight on the engine... and the starter gear isn't sticking any.

cheese's Avatar
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04-12-06, 12:42 AM   #3  
I see V8Driver has also had problems with no-name or aftermarket gears. Use genuine Briggs drive gears to avoid this problem. Another thing, especially on the twin cylinder flatheads like yours, check the starter bushing on the drive end. It gets worn and allows the starter shaft to push itself away from the flywheel ring gear while starting, and the edges of the teeth are the only thing touching. It soon strips the teeth. You can replace the bushing with one from an automotive starter rebuilder shop, or replace the drive end cap of the starter with one from a small engine shop.

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Bigwind's Avatar

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04-12-06, 02:01 AM   #4  
Hello all and Cheese. Could a low battery output cause this? Thx,

lilmatty's Avatar
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04-12-06, 09:32 AM   #5  
Thanks for the advise guys. The old gears where plastic. Seems like they should be metal but what do I know.

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04-12-06, 12:02 PM   #6  
A plastic gear has it's advantages. If the gear snags the flywheel , it breaks the plastic gear instead of other more expensive components. It also cushions the shock of engagement. I have an 18 year old Briggs IC single that still has it's original gear, so durability should not be a real issue. If you are breaking the gears repeatedly, look for alignment or wear issues as mentioned above.

Also, the debris that 'unwanted guests' often leave behind will cause problems. I take my recoil housing off every spring just to check. I have no 'secure' storage space, so little critters are a fact of life.

repair_guy's Avatar
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04-12-06, 01:44 PM   #7  
all this is true but,the plastic starter gear has a beveled side.
make sure this "beveled" side is towards the ring gear on the flywheel or this will keep happening.The beveled side is for line-up perpouses.

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