What tools and books are needed to rebuild a B&S push mower engine?

[MowManWV]

Naturally I am now thinking about a complete rebuild......"Little Murray's" shaft is bent.......rest of her seems fine though. I've done a rebuild before (25 years ago in a night class) and I have re-honed a cylinder......is this something I could do on my own?

Replace a bent shaft on a 3.5 horsepower push mower engine? I'm assuming I'd need new rings and bearings.

Where would I need to look up directions for this? Stuff like torque amounts?

What tools for this job?

THANKS

 

[bertsmobile1]

First of all we need engine numbers
If it is an aluminium bore engine then it is throw away the block and keep any good bits for spares .

 

[Scrubcadet10]

a replacement short block (New crankshaft, pison, all internals) you swap over flywheel, coil etc. 398211
replacement engine is 10T8020016,

 

[MowManWV]

Numbers on flywheel cover:

9L902-0221 E1 04062952

 

[StarTech]

Times has change a lot in the last 25 yrs.

The tools to do a proper cost more than a new engine especially for a one time rebuild. The Lisle 16000 ridge hone itself is around 150 usd. You would need this because a flex hone just makes any taper and/or oval worst. And this is just start as there other possible tools needed some of which are no longer available like the one to do the crankshaft bushings and the 1/4" valve guide repair (19269) tool set.

Basically the cost of the engine came down enough that Briggs decide to eliminate the tools plus they just weren't selling many of the tools as only us older shops were even doing these repairs anymore. By the time we buy the parts and do the repairs it is way more cost wise than just replacing the equipment when it come many of the walk behind equipment.

BTW that engine is a 2004 and is 17 yrs old. It had a long life and it time to retire it after major mishap as bending a crankshaft. The direct replacement is the 09P702-0116-F1 which Power Distributors is pushing a surplus 09P702-0144-F1 which around 240 usd which all that is left as Briggs is really screwed up lately. This is because of Covid and their bankruptcy.

 

[Anielytra]

Actually, what's the problem?
I don't think an old mower is easy to fix because there are no current parts on the market. My dad's old mower broke two years ago, and he found an audible review on fixing it. But it ended up that he still hasn't found a replacement for the broken part. Technology doesn't stand still, and new and improved gadgets and appliances appear daily. It's just not profitable for manufacturers to keep making parts for older models. In a market economy, everything has an expiration date. After a breakdown, the consumer buys a new thing because it's often not profitable to make repairs.

 

[StarTech]

His problem is a bent crankshaft for one, another is that the engine is 25+ yrs old.

It more about economics. The OP can buy a replacement mower for less than the replacement engine. Rebuilding the engine requires several hundred dollars of tools. The crankshaft alone is 120 usd then there is the gaskets. On top if he needed to OS the piston, it is NLA. Besides the short block is 160 usd. Then of course places like Walmart have complete walk behind mowers starting around 200 usd.

Now I have the tools but have not even had them out their boxes since 2014 as no one is willing to sink that much in an used engine that will still have worn parts afterwards.

The way engine manufactures are doing now is they try to make up for their deals equipment OEM is to stick it to the end user. They simply don't want to have stock engines just sitting in the warehouses collecting dust.

Bert can explain this mode of economics better.

 

[Fish]

I still have an old crankshaft straightening tool, it actually re-bends the crankshaft so it cuts level and doesn't vibrate. Works pretty good. I might have to do a youtube video of it.

 

[bertsmobile1]

Putting on the old metallurgists hat, I could not consider a more dangerous thing to do than to cold straiten a crankshaft apart from cold straitening cast motorcycle wheels.
The fact that the engine companies actually made such a tool flabbergasts me .
The chances of a "repaired" crank having a catastrophic failure in the future is so high it is not funny and made even worse by the use of bar blades which are naturally unbalanced because the bending moments are at 180 degrees to each other .

However Star is on he right track, time for a replacement engine
Downside is you can no longer get the higher torque side valve engines which are better suited to mowers than OHV engines so you will have to fit an OHV one.
Upside is it will use a lot less fuel .

 

[StarTech]

I seen those straighteners and even had plans for one. Then I was advised against them as they can cause micro fractures in the crankshaft. One fellow tech even had one crankshaft to later break off while the mower was in operation. Besides most of the engine I seen where on crappy poorly maintain mower bodies.