Tiller Engine

[USHorse 41]

I want to replace an old verticle shaft Briggs with a new engine. Looking at typical ones listed in Northern Tool and the likes but heard that these engines have an aluminum flywheel and for a tiller application, need a steel flywheel. Can someone explain why this would be needed.

:banghead:

[Kelly 1,033]

Just a guess, but I'd say the heavy flywheel is harder to stop or slow down, and would be a benefit for a tiller.

[theoldwizard1 2]

One little problem with a heavy flywheel. The old B&S horizontal shaft engines used a key between the crank and the flywheel that is designed to shear if something stops the engine abruptly. This moves the timing off and likely it will not start until replaced, even though the flywheel appears firmly attached to the crank.

I got lucky on a early 60s Simplicity tiller I was fixing up. It had dual counter-rotating output shafts. I was converting it to a Briggs Magnatron ignition so I had to pull the flywheel. That is when I discovered the sheered off key.

With the key replaced, the Magnatron ignition ($15 on eBay), a new recoil one-way clutch and a carb cleaning, my $30 investment started right up. Burned lots of oil because it had been siting outside for about 30 years and probably moisture had gotten in and rusted the cylinder. Sold it for $100 because I got a newer/better tiller (late 60s Wards/Gilson) for $50.

[USHorse 41]

Regarding timing, I do remember reading somewhere that the timing is easily messed up if a heavy duty flywheel is not used....so I think we are on to something there.

Not sure if new engine and heavy duty flywheel is worth the investment (about $260) as the tines on this old Agway tiller a so thin they only have one side :banghead:

[TT-(Moderator) 1,162]

It really has nothing to do with timing - it's more about balance and inertia.

The smaller B&S engines with the aluminum flywheels relied on something heavy on the other end of the crankshaft (rotary mower blade) so they wouldn't kick back when starting and so they would run smoother at lower speeds.

Even though they will run with nothing on the PTO end of the crankshaft, they aren't really designed to.

Engines with cast iron flywheels still used the aluminum key - even those with electric start. The taper is what holds the flywheel - the key is mainly for alignment when assembling.

The shearable key is actually a plus - especially if you've ever witnessed a Tecumseh with a split flywheel. :banghead:

[6wheeler 669]

TT, you are right on with that. On our pickup spray rigs, sometimes the product can get thick and hard to pump. Or sludge can build up on the impeller and make it hard to pump. So, the key shears.. Thank god. No broken pump shafts. I will tell you that it is a helluva lot easier to change the key than rebuild the pump. We carry spares in the rig and you can field change one in about a 1/2 hour. It seems that before any real damage occurs, the flywheel key shears . Probably caused by inertia but it works to our benefit. I don't know if that was the plan from Briggs, but is a real plus. I'd probably see if I could fix the original engine and put it back on. Pat

[USHorse 41]

OK, so if I read this correctly, the reason B&S is telling me to swap out the Al flywheel for the cast-iron flywheel on their replacement engine (via SEW) is that the cast-iron adds the needed weight during rotation to maintain balance and inertia when a mower blade or equivalent is not present? This now is starting to make sense to me.....thanks..USHORSE :banghead: