SO... does crack kill flywheels, too?

[Gumby83]

I had to remove the flywheel to replace the crankcase breather as the old one would “squawk” with the last few revolutions after key off. I didn’t figure that out until I was filling it with oil and my brain was going “Steady....
steady....
steady.....

DUMP ALL THE OIL INTO THE FUNNEL AT ONCE!!!” and the excess pressure vented through the breather, creating a much quieter but identical “squawk.” Aha!

I noticed the flywheel has a hairline crack in it on the flange surface for the shaft nut. I can’t say for sure how long it’s been there - I don’t remember seeing it the first time I took it off last year, and I’ve only had this engine running for a few minutes since my tear down. I only used a light coating of oil on the shaft (NOT the threads) when installing the flywheel, and I torqued the shaft nut to 150 ft-lbs per the B&S intek service manual I bought. The shaft, key, nut and washer are all in good condition.

I know cast iron tends to continue cracking once it starts, and when fully seated, there’s outward pressure on the flywheel not only from spinning but also from the interference fit on the shaft. I recognize there’s significant chance of injury and/or pants pooping to the operator and bystanders if the flywheel splits completely through.

Keeping that in mind, I’m not sure what to make of this one. It only appears to be in the raised flange area of the flywheel. The crack is visible on the inner and outer surfaces but no light is visible through it when holding a flashlight behind it, and it doesn’t look like it’s extending into the flywheel yet.

I didn’t know if this is a common thing among small engines and it’s nothing to worry about or if....

I can take more pics if requested.

 

[Scrubcadet10]

I rarely see a cracked flywheel... However, i wouldn't operate it like that much longer at all.

 

[bertsmobile1]

That flywheel is deceased and what killed it was the oil you put on the taper.
Tapers are always fitted dry

 

[Fish]

Throw it away, A flywheel like that can kill someone.

 

[Hammermechanicman]

C'mon man! Have some fun. Fire it up and over rev it till either the rod the govenor gear or flywheel blows. Place your bets gents. ?

 

[Scrubcadet10]

https://www.jackssmallengines.com/Products/BRIGGS-STRATTON/Flywheel/Flywheels

get the model and type number off the valve cover, that'll help you get the right one.

 

[Beamster]

Having designed building structures for over 40 years, cracks in metal are deemed a "run, don't walk" situation.

 

[Gord Baker]

I had to remove the flywheel to replace the crankcase breather as the old one would “squawk” with the last few revolutions after key off. I didn’t figure that out until I was filling it with oil and my brain was going “Steady....
steady....
steady.....

DUMP ALL THE OIL INTO THE FUNNEL AT ONCE!!!” and the excess pressure vented through the breather, creating a much quieter but identical “squawk.” Aha!

I noticed the flywheel has a hairline crack in it on the flange surface for the shaft nut. I can’t say for sure how long it’s been there - I don’t remember seeing it the first time I took it off last year, and I’ve only had this engine running for a few minutes since my tear down. I only used a light coating of oil on the shaft (NOT the threads) when installing the flywheel, and I torqued the shaft nut to 150 ft-lbs per the B&S intek service manual I bought. The shaft, key, nut and washer are all in good condition.

I know cast iron tends to continue cracking once it starts, and when fully seated, there’s outward pressure on the flywheel not only from spinning but also from the interference fit on the shaft. I recognize there’s significant chance of injury and/or pants pooping to the operator and bystanders if the flywheel splits completely through.

Keeping that in mind, I’m not sure what to make of this one. It only appears to be in the raised flange area of the flywheel. The crack is visible on the inner and outer surfaces but no light is visible through it when holding a flashlight behind it, and it doesn’t look like it’s extending into the flywheel yet.

I didn’t know if this is a common thing among small engines and it’s nothing to worry about or if....

I can take more pics if requested.View attachment 56028View attachment 56029View attachment 56030

 

[Gord Baker]

Nasty situation. I would carefully drill a 1/8" hole at the very base of the Boss at the crack site all the way through the Flywheel until you find a replacement. Do not over tighten, use a New Key.

 

[Gumby83]

Yeah I figured it was toast... but then I tried to eat it, and even peanut butter didn't help the taste! ?

I did some searching for machine shops in my area that might be able to repair it, but didn't have any luck due to either cost or down time, so I got a replacement flywheel and key ordered directly from Briggs & Stratton's website today (there was too much confusion on part numbers from other websites - I wanted to be sure I'm getting the right one and I wouldn't have saved much going elsewhere).

For clarification - the "light coating of oil" was residual spray lube. Whenever I have an engine apart, I coat all the internal components with spray lube to prevent rust after cleaning. The engine was apart for more than a week before reassembly, so I figured what little coat of lube was left on it could only help to prevent the flywheel and crankshaft from seizing.

I'll inspect the crankshaft more thoroughly before installation to make sure I didn't miss anything else that might have been a contributing factor.

Thanks.