Bade Installation on Lawnboy Insight 10685 Mower

itzbinniceAugust 1, 2014

Need help in installing the blade on a Lawnboy Insight 21 inch push mower.
Model# 10685 (2007), Serial # 270031296 with Tecumseh 6.5 HP Engine.

Sounds simple enough but I am baffled. I�m trying to help my 81 year old brother in-law who owns the mower.
He must have hit protruding tree roots and damaged the Blade Adapter (driver) part # 106-3987.

Here is the problem, the Tecumseh engine has a keyway running the entire length of the shaft. The damaged blade adapter has a small cutout in it that aligns with the keyway, the problem is the blade adapter does NOT have a keyway groove in it and must slide on the shaft without a key. I would have assumed the key is tapped in after the blade adapter is in place on the shaft. That confuses me since what is to prevent the key from flying off when the blade is spinning.
What�s more confusing is that the parts schematics for both the Lawnboy and the Engine do not show a key.
Why then is there a cutout on the blade adapter for a key The key is missing if there ever was one?. Also, without a key, is tightening the blade bolt keeping enough pressure on the blade adapter to keep it tightly in place?

Any help with this issue is sincerely appreciated since I have never seen a setup like this before.

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saltidawg(Z6 MD)

Same part on Toro....

Here is a link that might be useful: Video

    Bookmark   August 1, 2014 at 10:51AM
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saltidawg(Z6 MD)

Replacement parts....

Here is a link that might be useful: Here's The Parts

    Bookmark   August 1, 2014 at 10:53AM
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Thanks for the reply, I've already seen that video which is further confusing. I also have the parts schematics for both the Lawnboy and the Tecunseh 6.5 HP engine.

The video states "align the keyway on the driver with the keyway on the shaft, slide the driver on the shaft"
THERE IS NO KEYWAY INSIDE THE DRIVER, only a small cutout as shown in my pic.

More confusing is I've seen some Blade Drivers NEW on Ebay that shows that keyway cutout on the adapter as been welded closed. Looks to me like its not new but repaired.

    Bookmark   August 1, 2014 at 11:12AM
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saltidawg(Z6 MD)

I'm not a mower expert, but I suspect that the part is used on more than two mowers... I suspect in your application there is no key required.

Best of luck.

    Bookmark   August 1, 2014 at 11:37AM
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Thank you for your responses.

Toro now owns Lawnboy so part numbers are the same, so yes the part does fit more than one mower.

I agree it appears the Lawnboy does not have a key.
The only thing I can think of is that the shaft on the engine may have a slight taper to it and when the spacer that goes inside the blade adapter (driver) exerts pressure on the adapter to keep it in place without slipping. I can't tell if the shaft is tapered since I don't have the mower at my house.

I'll have a clearer picture when the new parts arrive that I ordered since the old blade adapter is pretty messed up.
BTW the blade adapter on the unit does have the cutout for the keyway unlike the one on Ebay that showed it was welded closed. I ordered one with the keyway cutout present.

Hopefully someone owning a Lawnboy 10685 can advise why the shaft keyway must align with the blade adpater (driver) when there is no key.

    Bookmark   August 1, 2014 at 12:32PM
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The blade bolt holds the driver on, and the blade driver has a machined-in key the indexes the groove in the crank. I don't even loosen the belt guard to remove the driver - after removing the bolt, just slip the driver down to get the belt off. The slip-off blade driver really makes belt changes easier.

    Bookmark   August 1, 2014 at 5:47PM
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Thanks saxman1 for advising the driver that has a machined-in key that indexes the key on the crank.

I did give it some thought and suspected that perhaps there was a ridge inside the driver that would slide into the cranks keyway. Not having the new part yet i just wasn't sure. The old one is in such bad shape I can't tell if that ridge was destroyed. I did have to tap the old one off with a hammer tapping each side of the driver uniformly to finally get it off.

    Bookmark   August 1, 2014 at 6:10PM
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Okay, what happened was the blade stopped so suddenly that the crankshaft over-rotated inside the driver, shearing or flattening the key. That must have been a violent collision. Assuming the crankshaft looks okay the new driver will fix it but unless you also ordered the fat spacer washer with it, you'll have to find the old one. It could still be in the old driver. The purpose of it is to locate the pulley vertically for belt alignment. The new driver should slip onto the crank shaft easily after you align the key ridge with the key slot.

    Bookmark   August 1, 2014 at 8:10PM
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@ saxman1

Thank you for explaining about the driver having a flattened key and the purpose of the spacer. I was able to retrieve the spacer from inside the driver and it appears OK.

I agree, it must have been a violent hit since it even damaged the threads on the hold down bolt which I'm also replacing along with a new blade.

The crankshaft is not bent since I tested it by running and no vibration but didn't cut grass, Upon inspection I found after the collision he took the blade off then put it back on upside down. That's what happens to some of us when we reach our golden years.

I should have waited to post since when I receive the new parts I would have seen how the driver locked on to the crankshaft.

I appreciate both you and saltdawg responding to my post.

Here is a pic of the damaged driver.

    Bookmark   August 2, 2014 at 8:55AM
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Wow. It ripped the machined key right out of the driver. Never seen that before.

    Bookmark   August 2, 2014 at 11:07AM
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Yes the keyway looks pretty nasty.

I'll post back after installing the replacement parts which should arrive mid to late next week.

The price for a new bolt on Ebay was absurd, cheapest I could find was 6.88 shipped.

I bought it from Jacks Small Engines for 1.85 plus 14.25 for a new blade and paid 7.95 shipping.

One Ebay seller was selling the bolt for 6.99 plus 2.95 shipping. That's 9.94 for a bolt, good luck to him finding a buyer.

    Bookmark   August 2, 2014 at 11:33AM
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