Predator flywheel on flathead Briggs?

Andrew05

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So I'm probably gonna sound like an idiot for asking this, but will a flywheel for a 212 Predator fit on a 5hp flathead Briggs? My buddy had an old 5 horse sitting under his porch which he gave to me, so I have no clue as to the history of the factory flywheel. That said, I've done some small stuff to it so I can put it on an old minibike including removing the governor. I'm also on a bit of a budget, so I was looking at one of those 8k rpm flywheels designed for a Predator. Does anyone know if they're interchangeable? I've looked at some pictures and it seems like they're close, but I figured I'd ask someone first.
 

G.W

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I love flathead briggs engines. As far as the flywheel goes look into swapping a 3hp briggs flywheel onto it.
 

Rat

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So I'm probably gonna sound like an idiot for asking this, but will a flywheel for a 212 Predator fit on a 5hp flathead Briggs? My buddy had an old 5 horse sitting under his porch which he gave to me, so I have no clue as to the history of the factory flywheel. That said, I've done some small stuff to it so I can put it on an old minibike including removing the governor. I'm also on a bit of a budget, so I was looking at one of those 8k rpm flywheels designed for a Predator. Does anyone know if they're interchangeable? I've looked at some pictures and it seems like they're close, but I figured I'd ask someone first.
Diameter isn't the only concern you need to be concerned with, keyway size and shaft taper are going to be the make or break factors.

I strongly suggest you find someone you can borrow a stock 212 flywheel to test the fit and compare the keyway before you try to go full send on it.

A well tuned flathead with a straight pipe has a unique exhaust note unlike any other engine... no lawn engine sounds further from being a lawn engine than a straight pipe Briggs Flatty
 

Andrew05

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@G.W I've thought about that too, I assume I would need a bracket to relocate the coil? Also can they hold up to rpm? I read something on the Bob's Karting forum (linked below) that some folks could turn about 8500 without breaking a sweat so I assume running at 6000 for an extended period would be just fine. I've got an old Briggs push mower in the shed I might be able to use.

@RLS_Underground We just got a generator with a Honda clone motor I might be able to compare with, but I'm not sure how happy my dad would be with me pulling that apart lol. I love the sound of these older flatheads too, I was gonna swap to a Predator but I just couldn't do it. I'll look around and see if I can find something or I may go with G.W's suggestion for a 3 horse flywheel.

 

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Oh yeah the 3hp flywheel will hold. That's how it used to be done before billet flywheels were affordable. I've seen 5hp engines with a 3hp flywheel rev up to 9k(not recommended) and not blow. You would need a bracket to move the coil down, but it isn't too expensive last time I checked. I've got a 5hp flathead I need to build up for my mini bike
 

Rat

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I've got an old Briggs push mower in the shed I might be able to use.
If it's a 3, 5 or 5.5 B&S flathead it should work despite the shaft orientation difference, there's ironically not a lot of differences between the horizontal and vertical B&S engines beyond the cover.
@RLS_Underground We just got a generator with a Honda clone motor I might be able to compare with, but I'm not sure how happy my dad would be with me pulling that apart lol.
Don't Bother, If it's a true GX160 or GX200 clone the taper is not the same as a predator 212, and the flywheel is 1/2" larger diameter... the keyway and taper is likely to not match as well
I love the sound of these older flatheads too, I was gonna swap to a Predator but I just couldn't do it.
As much as I hate Predator engines, it's going to give you the most in the long run. The EPA cracked down on lawn equipment emissions which is why all new mowers run an OHV/OHC engine and likewise flatty parts will begin to dry up.

I've got an oddball 4hp I can't get parts for because it's the one engine B&S made that does not interchange much if any with other B&S engines. I mean the parts I need for it are impossible; the head gasket is bigger than a 3hp but smaller than a 5... I don't want to fuss with making one. The case cover is a sleeve bearing (irrigation pump engine) and I'd need a sealed roller bearing to do anything even half serious... I did get it running despite being full to the brim with water though.
 

Andrew05

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Checked out the mower, it's a OHV Briggs 300e series engine so I highly doubt it'd work. @RLS_Underground Thanks for the info, I figured all Honda clones were essentially the same engine, just with varying quality. And my original plan was to get a Predator and do some stuff to that, but due to budget limits I figured I'd stick with what I had. I appreciate the info from ya'll! I'll keep my eyes out for a 3hp flywheel, and I'll just swap one of those on.

Also @RLS_Underground not sure if this would help, but would this fit your 4hp?
 

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not sure if this would help, but would this fit your 4hp?
It probably will, but I'm still going to need to hunt down a side cover lol to use the engine... I'm not married to the idea of using it although I've already put work into it
 

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It probably will, but I'm still going to need to hunt down a side cover lol to use the engine... I'm not married to the idea of using it although I've already put work into it
If you were closer I'd give ya one lol. I have one that I tore down for parts that had some internal issues. I was saving the cover for if I needed it for another one lol.
 

Rat

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If you were closer I'd give ya one lol. I have one that I tore down for parts that had some internal issues. I was saving the cover for if I needed it for another one lol.
Shouldn't he ridiculous to ship but I'd need measurements and pics before I'd consider it. I've already gotten burned by parts that "should" fit.

Like I said 4hp is the one oddball that not much swaps with from the 3's or 5's
 

G.W

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Shouldn't he ridiculous to ship but I'd need measurements and pics before I'd consider it. I've already gotten burned by parts that "should" fit.

Like I said 4hp is the one oddball that not much swaps with from the 3's or 5's
He claimed it was a 5hp in his post. If not I do have a 4hp, but he will.have to wait because that engine is in a completely different state (long story)
 

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He claimed it was a 5hp in his post. If not I do have a 4hp, but he will.have to wait because that engine is in a completely different state (long story)
I'm in no major hurry. It's for a second project build that I'm still working out a few particulars on how I want to do things.
 
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Thepartsguy

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$145 off arc once.. blow the engine up pull the arc flywheel put it on another $20 Briggs flathead.. But you will always have the flywheel. I actually opted to spend a little more for a 3hp flywheel from arc.. that way I could have fun with junker 3hp’s and 5hp‘s also.. after awhile you might buy a $70 rod.. Then on the Briggs forum looking for a 93ss. Mild 5hp had me going 50+ and smoking 8hp’s off the road from a roll race. But from a dig by the time I got the little 5hp moving the 8hp was already a mile ahead..
 
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G.W

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$145 off arc once.. blow the engine up pull the arc flywheel put it on another $20 Briggs flathead.. But you will always have the flywheel. I actually opted to spend a little more for a 3hp flywheel from arc.. that way I could have fun with junker 3hp’s and 5hp‘s also.. after awhile you might buy a $70 rod.. Then on the Briggs forum looking for a 93ss. Mild 5hp had me going 50+ and smoking 8hp’s off the road from a roll race. But from a dig by the time I got the little 5hp moving the 8hp was already a mile ahead..
I have plans to hop a 5hp up and put it on my mini bike, and hop up a 3hp and mount it up to a bicycle.
 

Thepartsguy

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I have plans to hop a 5hp up and put it on my mini bike, and hop up a 3hp and mount it up to a bicycle.
Cleanliness.. Were not talking sealed air controlled factory cleanliness.. Just even take a stock 5hp apart and clean it like your trying to make it look new. Some paint and put it back together stock with even light mods. You know a 5hp Briggs is setup from the factory to never reach true wide open throttle. The butterfly is offset to only open to about 65% throttle. Take apart clean dr-restrict and put back together. They don’t even need hopped up a ton to preform. a rod and flywheel at minimum.
B8A4C55F-AED7-4DC7-AF34-E116CFA0CE9A.jpeg0572F8B7-BF1D-4C07-ABC3-102061D2FAD4.jpegC2ABD307-4D2A-4C1D-AB86-5BADCB1262A0.jpegD0E0F1A7-5924-4B4B-8B82-506BBD01E2C6.jpeg
 

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I just wanna do.some minor port smoothing and polish the exaust. Rod and flywheel of course. Maybe shave the eyebrows and get a bit more compression by shaving a few thou off the head. And of course a spicier cam.
 

Thepartsguy

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I just wanna do.some minor port smoothing and polish the exaust. Rod and flywheel of course. Maybe shave the eyebrows and get a bit more compression by shaving a few thou off the head. And of course a spicier cam.
Be careful what can you get as the flywheel is 30* advance at the key. With a 2.somthing pound lightweight flywheel and all that advance.. imagine you got a cam with no compression release.. the Kickback could become brutal. a 93ss or hotstock equivalent cam. That way your not looking to have the lifter area welded. And the cam still has the comp release with all the advance from the flyhweel. Port cleanup is good. I hogged both int/exh so the ports were a bit “closer“ so to say. the stock tanks are amazing with simple mods to it.
 
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I was thinking of getting the stock cam ground to a mild lift. Maybe I'll get it lightened too.
 

Thepartsguy

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I was thinking of getting the stock cam ground to a mild lift. Maybe I'll get it lightened too.
Stiffer springs from DC are expensive when you add on the $30 shipping.. You can use a stock exhaust valve spring in place of the stock intake valve spring. little less float in the higher rpm’s.. I’ll have to check eBay.. Briggs racing sidecovers are $80 and I believe they had the cam bearing upgrade but I’m not 100% if they do I’m getting two of them.
 
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