The Home Machinist!

The engine is only 8 hp. It is a 19D Briggs & Stratton with the heavy flywheel. The initial attempt to remove it, was the two bolts close to the shaft. One bolt broke flush into the flywheel. An attempt to drill through that bolt allowed the drill bit to wander and it broke. The drill end was picked out.There is still mess to secure a pull close to the tapered end of the crankshaft. He has tried heat and various outside pullers ( would have to have jaws expanding over 9 1/2") and then coming behind the flywheel. It is all one piece. I know that 9 1/2" doesn't seem much but there isn't any space for thick jaws to get around it.
Dang. The way is, to weld into the broken stud and pull from the center. Same deal but heavier. Tapered shaft, been on there 50 years.
Questions: and answers maybe. While welding the stud there will be so much concentrated heat close to the shaft, it may release. The ground or return must be placed close to the electrode, for it may try to weld the shaft. It would certainly excite it
At this point, he has heated the flywheel and used all manners of penetrant.
Yes questions and Answers

Fabricate a really stout puller and then use an impact wrench? How big are those studs?

The original stud holes are 5/16 X18 tpi. He used higher grade, shoulder bolts. If the flywheel was off of the engine, repair would be easy. It is soaking upright with Kroil now. He has a brake drum puller applying tension.

I am somewhat embarrassed for even posting about this engine. It is one of those little things which perhaps, doomed that design. The "key" was external, bearing within the key slot used for drive pulley. The taper within the heavy flywheel may have moved, creating a scored locking surface. This needs raw power to remove closer to the center. Forget 5/16 X 18 . Those days are over but a fixture could be assembled to guide an end mill. It will require both locations milled through, to at least , a thread of 3/8 X 16 can be threaded into the iron.

I'm not there. The same design of the puller could be the guide. This is awkward stupid compared to larger engines of more importance but is the correct engine for a certain small tractor.
Sure. Bring the engine to a milling machine. There are metal guards which cannot be removed until the flywheel is off. Fixturing this thing dead on the table.. supporting behind a flywheel with 3/16" clearance.. wasn't the way.

I will visit and we will get this flywheel off. The reason is more than a wire behind it -to the magneto which is no longer isolated. The flywheel has shifted on the tapered shaft. that's all. no big deal.

I've run around a few ideas but the engine has been sitting under a bench for a while. He is looking for a decent drill press. Need to make a guide which ends up being a puller. The existing pull hole and the crankshaft OD will be the center hole. The third hole will be directly above the broken bolt and act as a guide for an end mill.

Spro, If I understand you right.....You have a flywheel on a motor that you are trying to remove from a shaft, which must be done in place because you can not remove the motor from the unit. A bolt has been broken off in one of the threaded holes that is used to jack the flywheel off the shaft!? Is this correct and if so... Does the shaft protrude past the flywheel? If so....you may be able to make a jig as a drill guide that would allow you to use different sized drill and end mills in a hand drill to get the broken bolt out and drill larger holes for greater strength to jack the flywheel off the shaft. The jig could be built in place, with a little welding, using the existing bolt hole and then swung 180* for location of the damaged hole.
I drew this up to to give you and Idea of the set up.
The green part is the jig and the gold part is a drill bushing that could be make to the size required for the operation at hand.
http://a360.co/2nSr6eC
I am not sure if this would work, but it is an idea.
Good luck.

Here is the picture loaded on the server, no need for the link. I am learning as I go sometimes!

Hi Patio. Yes you have the idea. My guide would end up being the puller and I started describing it but became lost in the details. The fixture is similar to your example except the opposite side extends to be located at the useable bolt hole. It will need to be fixed fairly sturdy in order to keep the mill straight atop the broken bolt and wandered-off drilled hole. It is a tapered shaft within the flywheel and short threaded section which held an external "key" under the flywheel nut. The slotted crankshaft extends some 3"- 5" beyond that. It is somewhat a puzzle because I don't have exact measurements and may need to rethink this. I like your idea of drill bushings. If I go to this, it will be more than a one-time puller for this particular occasion. Thanks !

In addition to a stronger puller attachment (more and bigger bolts?) you might try a protective sleeve over the crankshaft that would permit use of a really heavy hammer or air hammer. Something like the old 'axle knockers' we used to use to knock the tapered axles out of brake drums. My dad used to say "Hit it like you mean it!". I do not like to put much tension on the rims of such flywheels.

I've had my fair share of very stubborn flywheels on Honda's and Briggs engines. These engines are air cooled and typically see 350-400* temperatures, so it takes a lot of heat to hurt the flywheel. Several heat cycles using a propane torch to evenly heat around the center of the flywheel will expand and contract the flywheel and then with a good quick whack to the crank end while holding the engine by the flywheel it will typically let go.