Sportsman Flyer Build

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I was surprised of the weight of a ARC 6671 flywheel. 180 from the epoxy encapsulated rare earth magnets is a encapsulated counter weight. The stock ARC has a bit of spark advance. When I get the cast iron flywheel off so I can compare weight, will be worth documenting. Never gave it any thought until right now.
Those d**n fan blades create drag too ! Grrr!
If I don't get the performance I expected, chips will fly. Four jaw chuck to the rescue.
Wanted to remove the cast iron flywheel before any thing else got done.
It's in the way if I have to shorten the protrusion on the crankcase that supports governor axle.
The axel gets driven out leaving a hole in the crank case so I will drill the axel and governor bores with a letter C drill and tap 1/16- 27 NPT. I have plugs for both.

So I gotta get the flywheel off, socket wrench on the nut, Halder Supercraft dead blow, and I'm beating away. Nuthin.
Well that was yesterday, and I reviewed selected scenes of both AGK and ARC. I decided, I was driving the nut wrong way.
It happens even to a good man I am told. Back on the bench this afternoon. Wrench and hammer whacking away counter clock wise. Still nuthin.
Plan B. Couple of years ago I purchased a Porter Cable electric impact driver 1/2" drive. Weighs more than a small dog.
Pulled the trigger and off comes the nut, starter cup, and plastic fan. Small leap for mankind.
Nut back on the crank shaft to guard the crankshaft threads, I gave that nut some fierce licks with the Halder hammer.
Nuthin again, I got a trend going. (^) So I breaks out the heavy artillery. Estwing Special Edition Fireside Friend Axe - 14" Wood Splitting Maul with Forged Steel Construction & Genuine Leather Grip - EFF4SE: Home Improvement
Nice rap and the iron flywheel is off it's taper at last. Copper chisel and 4oz hammer free the woodruff key from the shaft.
So I got this cast iron flywheel in one hand and this high toned CNC machined be all end all aluminum (Brits say different)
Flywheel in the other. Hmmm. Take them in the house to Grand Dads scale.
Cast iron was a smidgeon lighter than the 3lb ARC flywheel. Tempted to get in touch with ARC and ask WTF? Anyway.
Back to the shop. Took forever to find my Dykem Prussian Blue. Wasn't where it was supposed to BEER!
To me it a goodenoff fit I will not do the lap routine.
The 65 ft lb torque and keyed flywheel crankshaft assy. has my confidence. Besides there is a local car show May 15.
Some photos.


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Drilled letter C drill through both governor crankcase holes. The governor axel support hole is cast as boss like feature on the exterior of the crankcase, flywheel side. AGK recommends reducing the height it stands up off the exterior of the crankcase so as not to engage the flywheel. I found in my tooling a counterbore with a pilot matching the holes drilled.
Luck? I think so. The governor boss thusly was shortened by 3mm. There after both re-drilled bores were tapped 1/6-27.
Plugs installed. All of the above took one hour and one beer.
Still got a bit of cleaning crankcase wise. But that is it, I think. Next thing on this adventure is reassemble all I took apart.
A torqueing I will go, a torqueing will go.....
Therein is a problem. All the video's use those clicky preset torque wrenches.
Mine have either pointers or a dial. At my age (70) retooling reflects my Peter Pan syndrome.
I think I caught from a neighbor 60 years ago.
Stick with what I got or more to add to the auction when I croak?
In the shop for about a beer. Primarily to seat the ARC flywheel on the crankshaft taper.
After cleaning out the Prussian Blue.
The stuff gets around like Bear $hit roofing tar.
Just drew up the flywheel mounting nut to firm, not torqued. There is about 1.5mm clearance now between the flywheel and the governor axel boss about 1.5mm. Torqueing the flywheel nut to 65 foot pounds will be the challenge.
ARC has a way of locking the crankshaft, from output side I need to investigate or use a strap wrench on the flywheel.
A strap wrench is locally $27. Used maybe once maybe? I have been thinking of other methods to secure the flywheel.
Plan B again, again. So ARC has a in house made crankshaft locking tool used when torqueing a flywheel nut.
I gave serious thought to making one, but unless I do more than one of these up grades it is pointless and my heirs will have no clue and dumpster my work. So KISS. Many times in my life immobilizing a precision round surface was necessary.
Using copper or aluminum of sufficient thickness to guard the jaws of Vise-Grips being the most common griping tool.
So once more eureka!
3/4" copper water tubing walls are thick and grippy. So I turned the engine crankshaft key way to face the moving jaw of the Bridgeport vise.
Sleeved the 2" x 5/8" dia. key slot area with copper tubing. Orienting the shaft keyway into a vise jaw for maxim grip.
Torqueing to 46 foot pounds was Duck Soup. Crankshaft never budged. KISS wins again.


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So the ARC Racing flywheel is torqued to spec. Time to lace this engine up. Without the video's of AGK and ARC Racing, I most likely would farmed the work out.
Thing I learned from AGK. Don't mangle valve seats so you have to recut them. My solution is patent pending, Just kidding.
ARC doesn't mess around. But if you want to go past their keyed timing you will have to lap the flywheel taper to match the crank shaft taper. As I did no lapping of the crankshaft flywheel taper, when drawn up, to the 46 ft lbs all clearances were in the + 1mm range. Empirical data is wanting.
Got me one coming Flex-Hone BC 3/4" Honing Tool: Industrial & Scientific
Intake and exhaust ports are not up to my standards, (Critiquing my own work)
A new forumite has inquired about engaging
Peterson Precision to do for him what I have done for myself. Port, polish, deck the head, and remove governor.
Flex-Honing the ports will distinguish my work.
Another thought, steel masking shields to obviate the worry of damaged valve seats, while cleaning up combustion chamber. Gonna do it.
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Trip to Ace for six M6x1x30 flange head bolts, verified timing marks one more time, and slipped the side cover on.
As per AGK, side cover bolts are torqued 96 inch pounds.
So I did the best I could, my In lb - Km torque wrench is a fifty year old Monkey Ward analog. Like beam and pointer kind.
Felt right when the pointer hovered at 100 In lb with my reading glasses on.
I would have finished the close up, but I am holding out for the 320 gr Flex-Hone to arrive.
Nothing like a proper cross hatch surface.
3/4" flex-hone arrived by mail today.
Chucked the Flex -Hone shank, in my cheap cordless drill, and gave the 79cc predator engine ports a go.
My drill RPM must have been a bit high or my elbow action slow, cross hatch was not the ideal 45 degrees. 30wt for lube.

Washed the head again with Dawn dish soap with tooth brush. Rinsed in super hot tap water, hand dried as best I can.
Then into a 200F oven for a hour or two to cook out any lingering moisture.
45 degree cross hatch it has not, more like 30. But uniformity was the end game, and uniform there is.

Time to lace up the engine. A static run up has been considered. No sense mounting it in the Flyer un proven.
Lord knows I have stock engine parts up the bazooty
Don't expect immediate progress though. Sunday is quality time with Miss Daisey.
Foot note;
Elves have absconded with six 6x1x30mm flange head bolts. I will seek them no further
I should have finished fastening the stock Predator engine mount to the engine block and bolting the engine mount to a poplar board. That board I will / did clamp in a bench vise. This is all just to create a secure system for the rest of the engine fastener torqueing. I just didn't like the AGK way of holding an engine being torqued.

If you recall, instead of as AGK does, machining the portions of the valve guides protruding into the valve guide pockets.

I chose to press the valve guides back flush with the valve pockets and then having to mill off some of the intake valve guide to fully seat the intake valve guide seal to the valve spring seats.
I never checked when I pressed the valve guides in, to see if any metal deformation had occurred. It had, but it was only on the exhaust valve guide bore had metal deformation, like crushing and collapse occurred. May be a .015" per side.
Valve stem would not go in.
The solution was a conical H.S. burr driven with a electric hand drill, gently.
The resulting chamfer, allows free valve stem passage. Lesson learned. Press valve guides with copper drifts.
Both valve stems now are free in their guides. Lacing / assembling, now unencumbered.

Wanting to get the Sportsman Flyer to the. Classic Car Show - May 15, 2021 (

Told Pat, if he would work with me I would be his Mid West ambassador. That's the plan.
Sadly I have no business cards for Sportsman Flyer.