Flywheel question

[Billsboats]

49 cubic inch 3 cyl flywheels?
are there any years that are more desirable possibly lighter?

[sharpeye Mike]

The 65 hp from 1972, it looks like a shallow soup bowl, it weighs in at 7.8 lbs. compare to 10.8 lbs.
Mike

[LittleCharger]

The 65 hp from 1972, it looks like a shallow soup bowl, it weighs in at 7.8 lbs. compare to 10.8 lbs.
Mike

I was always told that the claimed 7.8 lbs was unfounded as most guys found when they weighed them they were just under 10 lbs.

[stinger]

Thats the one.Small ring gear.Use with the unpotted,adjustable sensor timer base.Potted later model timer bases can be used,the potting on the upper inside edge requires machining for clearance of the flywheel hub.The best obviously is the racing Mod 50 F3 flexplate,came out as pink or gold colours.The earlier model pink flexplate is slightly lighter.

[stinger]

These are the ones.

[Billsboats]

of either type?

[sharpeye Mike]

The mod 50 flywheel would be expensive and hard to come by, but the 65 hp are still plentiful and cheap, I pick mine up for $ 20. Marinas are the places where I find the stuff I'm looking for.
Little Charger, I have both on the bench so weighed them, 3 pounds even.
Mike

[LittleCharger]

The mod 50 flywheel would be expensive and hard to come by, but the 65 hp are still plentiful and cheap, I pick mine up for $ 20. Marinas are the places where I find the stuff I'm looking for.
Little Charger, I have both on the bench so weighed them, 3 pounds even.
Mike

Good to know Mike, the ones the other guys are trying must not be the correct ones.

Cheers,

[Billsboats]

are you saying a 3 pound difference?
what needs to be done to the timer base to fit under that flywheel? got one we can see?

[sharpeye Mike]

Yes, a 3 pounds difference, from what I've been told the 72-65 hp is the only year that can be used. As for the installation I'm not there yet on my project (to busy) but looks like I have to machine a small ridge on the inside top surface.

[ultrafast30]

is this part no 580810??

[sharpeye Mike]

Part # is hard to read but it looks like 580904 but I could be wrong.

[ultrafast30]

Was yours turned down on a lathe. The ones I am finding have a groove for a starter rope.Maybe I need to keep looking!!

[sharpeye Mike]

No, I haven't turn it down yet, mine has a small grove on top of the ring gear for a rope also. Stinger has a picture of it on post 5, that's the one you want.
Mike

[sheuninck]

mine weight 9 lbs.
see pics

[Billsboats]

on a 3 cyl 75?

[sheuninck]

the 71 and less had the coils under the flywheel, the 72 did not, the 73 and on where the 10lbs flywheels. The old EP and FE rules called for the 10lbs flywheel. Mine work as i have raced with them with part #580810. the brp site says the part number is 580956 http://epc.brp.com/ There is minor interference with the potted type timer base at the inner top radius. Either machine the timer base potting or the flywheel.

[sharpeye Mike]

Ok, well mine is similar but not exactly the same, for example serial # is 580904, the ring gear is set at the very bottom of the flywheel, has two series timming # from 36* to tdc and mine actually wheighs in at 8.2 lbs, the darn thing gained 0.4 lbs, that's what happens when they get into the chocolates.
Sorry for the lack of pics but I'm not a gadget guy, I just figured out how to stop the vcr from flashing 12:00....I put a piece of tape over it.
Mike

[Billsboats]

there are a few 72 65 hp flywheels on ebay but that one you are talking about the 580904 is not coming up do you know what the application is for it?

[sharpeye Mike]

I hear ya, i did a search on it too and came out with nothing. All I can tell you is that the flywheel did come from a 65 hp, I was there when the guy took it off and because of the shape off it, I didn't question the year. Now I know it wont just slip on, there's a small ridge on the inside to machine out other than that it should fit like a glove,,,umm with the help of a ballpeen hammer. :)
Mike

[Billsboats]

Ball peen hammer??

[sharpeye Mike]

Well, sometime I use a sledge hammer for the stubborn ones lol.

[stinger]

The pic of the flywheel i posted i machined in the lathe.Casting # of 580810.Part # is 580956.

[ultrafast30]

Stinger,
How much weight did oyu take off what is the diff in the two?

[Bill Gohr]

Why don't you get rid of the confusion and post a pic of the heavy one and the 72 one together? Its obvious the difference, the 72 wheel is the only one with the thin ring gear and center hub magnets, looks like a 71 but a 71 had battery ignition and no center hub magnets, And if you see a 73 hangin on a rack somewhere dont count it out, the first production 73's had the light wheel too.

[David Mason]

Use caution if you decide to put on in a lathe and turn it down. I personally have seen these flywheels come apart and strike the driver. (racing application)

If you can find the light one, just bolt it on, and don't mess with turning it down. I don't think the real, real lightweight stuff has any serious advantages that can't be overcome by a prop and boat design. Not worth a grand for a flex-plate in my opinion only. I know others swear by it. I have not had any issues using a stock flywheel and winning some races.

Good luck on your project.

Dave

P.S. - You can find those flywheels in the junkyards if you look close.

[ultrafast30]

I just purchased one. It is untouched and in good condition. I have however, spun modified v4 flywheels on a v6 to 9000 rpm without issues. Had better luck with the yamaha ignition on the v6. I used to build those, still got 2 flywheels left?

[Billsboats]

maybe some pictures?

[sharpeye Mike]

Why don't you get rid of the confusion and post a pic of the heavy one and the 72 one together? Its obvious the difference, the 72 wheel is the only one with the thin ring gear and center hub magnets, looks like a 71 but a 71 had battery ignition and no center hub magnets, And if you see a 73 hangin on a rack somewhere dont count it out, the first production 73's had the light wheel too.

So, mine came off a 65 hp, shallow soup bowl shape like the previous picture, it has a thin ring gear but does not have the center hub magnet, so what is it from? Can I still use it?
Mike p.s. Fast Fred must be testing us on this one.

[stinger]

Mike.Read Bill Gohrs post SLOWLY .Your answer is there.

[sharpeye Mike]

What confuses me is that my flywheel did come off a 65hp but there's no 65 in the parts list in 1971.
Mike