flywheel n coil compatibility for older points style briggs 2, 3.5, 4 HP motors

A SIMPLE PLAN

A SIMPLE PLAN

Member
rebuilt 2, 3.5 n 4 HP briggs engine for fun. they did not come with flywheels or coils. got new coil and used cast iron flywheels. the motors were the OLD POINTS Style (no longer points, they are gone) ignition. question: will standard Briggs 2, 3.5, 4 HP flywheel work with new regular looking coil, w/o the little nib ... 3rd leg... on the coil? i looked up the part # somewhere, got that part # coil; but before i give myself a stroke/heart attack trying to start the thing/s i need to know, will the cast iron flywheel i purchased separate from engine and the coil i purchased separate from engine... work? read something abt... 2 magnet flywheels? the flywheels i have seem to have ONE MAIN magnet and then another 1" long... looks like magnet or something on the flywheel? to me a flywheel is a flywheel is a flywheel... a coil is a coil is a coil... if it works. on other post i read that the Briggs cast iron 3-5 hp flywheels can take over 6000 rpm... if not dropped/beat on, etc. is that correct? thx
 
A SIMPLE PLAN said:
rebuilt 2, 3.5 n 4 HP briggs engine for fun. they did not come with flywheels or coils. got new coil and used cast iron flywheels. the motors were the OLD POINTS Style (no longer points, they are gone) ignition. question: will standard Briggs 2, 3.5, 4 HP flywheel work with new regular looking coil, w/o the little nib ... 3rd leg... on the coil? i looked up the part # somewhere, got that part # coil; but before i give myself a stroke/heart attack trying to start the thing/s i need to know, will the cast iron flywheel i purchased separate from engine and the coil i purchased separate from engine... work? read something abt... 2 magnet flywheels? the flywheels i have seem to have ONE MAIN magnet and then another 1" long... looks like magnet or something on the flywheel? to me a flywheel is a flywheel is a flywheel... a coil is a coil is a coil... if it works. on other post i read that the Briggs cast iron 3-5 hp flywheels can take over 6000 rpm... if not dropped/beat on, etc. is that correct? thx
Click to expand...
Flywheels and coils need to be a matched pair -- that is, they need to talk to one another and charge/fire at the correct time. Typically a single magnet flywheel will use a two leg coil. A 2 magnet flywheel will use a 3 or 4 leg coil. You can tell if it's a magnet inserted in the flywheel by touching it with a screwdriver.
You also have to consider if the keyway is machined in the correct location and orientation with the magnet(s.)
The cast iron flywheels can sustain 6000 rpm and have for many years in karting if they are not abused as you mentioned.
Be careful with a lot of small displacement Briggs engines as they used cast aluminum flywheels on some applications (vert. shaft push mower, etc.) A cast aluminum flywheel is an explosion (and ensuing ER visit) waiting to happen.

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🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Just ran into similar deal yesterday on an old point style briggs that wouldn't run. The owner purchased a replacement non points style coil because the tiny primary wire on the original was broken. I should note this has the iron, single magnet flywheel. Still no spark. Turns out the new coil configuration has the windings spaced 3/4 inch away from the flywheel. A different new coil was correct and the spacing was very close like the original. After that, it was good to go, fired on second pull. You may want to verify the aluminum flywheel key is intact, as this one was sheared somewhere in the process adding an extra bit of diagnosis. Hope this helps.
 
good to know. i purchased this coil... Ignition Coil For Briggs& Stratton 793295 398593 591420 496914 793281 it was stated to fit the 2...3.5-4 HP engine. its got the oval holes; not the squared cube holes (for 5 HP?) .it fits..
flywheel has 1 magnet. so shd start? optimum torque for flywheel nut? 55 ft/lbs, Y/N? thx

1652990823045.png
 
CarlsonMotorsports said:
Flywheels and coils need to be a matched pair -- that is, they need to talk to one another and charge/fire at the correct time. Typically a single magnet flywheel will use a two leg coil. A 2 magnet flywheel will use a 3 or 4 leg coil. You can tell if it's a magnet inserted in the flywheel by touching it with a screwdriver.
You also have to consider if the keyway is machined in the correct location and orientation with the magnet(s.)
The cast iron flywheels can sustain 6000 rpm and have for many years in karting if they are not abused as you mentioned.
Be careful with a lot of small displacement Briggs engines as they used cast aluminum flywheels on some applications (vert. shaft push mower, etc.) A cast aluminum flywheel is an explosion (and ensuing ER visit) waiting to happen.

-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Click to expand...
ER if "lucky". engine builder revving up new motor in the car, 4 ppl standing around... harmonic balancer came apart... 5" piece of it hit him in the chest... any worries he had came to an end shortly thereafter. BEAT the balancer on the crank snout and cracked the cast iron? instead of pulling it on with balancer install tool? car craft did 8 cam swap on dyno. 2 piece timing cover, had machine shop open up the balancer so it was a press on easily fit since on dyno time is money. its not like it is going anywhere, once the bolt is tightned to spec's.
 
I caught a piece of the old tiny balancer for 283 sbc used on a 350 stock car motor.

Came thru the mud screen, bounced off inside my steel roof and hit my faceshield dead center. We were in full on race mode entering the corner. Slapped my head back against the headrest on aluminum seat and bent it.

I didn't know what it was as it rolled down in my lap.

After the race, I found the piece and returned it to the car I had been following.
I reminded him those were not legal in our class.
Face shield had a nice star in it.

Got lucky once. Used that up already. Just use the best safety equipment you can.
It can affect more than just yourself.
 
A SIMPLE PLAN said:
good to know. i purchased this coil... Ignition Coil For Briggs& Stratton 793295 398593 591420 496914 793281 it was stated to fit the 2...3.5-4 HP engine. its got the oval holes; not the squared cube holes (for 5 HP?) .it fits..
flywheel has 1 magnet. so shd start? optimum torque for flywheel nut? 55 ft/lbs, Y/N? thx

View attachment 22501
Click to expand...
That is the one we couldn't get to work. The one that did work had the coil body (windings) spaced much closer to the flywheel, or down near the curved sections of the mounting legs pictured above. It also had a metal tab on the composite coil body facing the flywheel. Sorry, don't have a photo, but can try to get part number. Believe it to be a briggs coil but not certain.
 
Allan said:
That is the one we couldn't get to work. The one that did work had the coil body (windings) spaced much closer to the flywheel, or down near the curved sections of the mounting legs pictured above. It also had a metal tab on the composite coil body facing the flywheel. Sorry, don't have a photo, but can try to get part number. Believe it to be a briggs coil but not certain.
Click to expand...
that is the one u cldnt get to work? (sigh). one that did work had windings closer to flywheel. a metal tab on coil facing the flywheel? yes a part nbr wud be good. so i dont waste $ needlessly on parts that dont work. i rebuilt the motor, just didnt come with old tired coil or flywheel. got flywheel one magnet. just wud like it to run the first time around.
 
which coil? the one i put in my post.... or the one that u are talking about that has the coil closer to the flywheel? what is the coil that i need to have on what was once a points style ignition, but points are gone now? a stand alone coil ?
 
Coil that worked was an "Oregon" brand, part # 33-340. OregonProducts.com . Oddly enough the interchange number is for the briggs 397358 which is the one you pictured and they are not the same. Possible I guess we got a misboxed one and just lucked into it. I'd bet Flathead is right and the one pictured is points triggered. Good luck!
 
this one is the one that worked for you... without points on a previously points style motor? it is stated to fit 5 HP engines. 5 HP coils are different size than the 2, 3.5, 4 hp engines cuz the flywheel on the smaller engines is smaller in diameter so the mounting posts are just a LITTLE bit different ... where cant get the mounting screws in the coil to mount it.

this is the Oregon part # 33-340. the coil part is closer to the flywheel





1653437246332.png
 
That is the coil. We put it on a 3.5 hp early tiller engine that used to have points. Hardware store on the screws I'd guess.
 
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