Back from the dead

Tom from Rubicon

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My son Derek, has about 7months left on a 22yr.hitch in the Navy. I keep telling to move to high ground as in Wisconsin.
He pulled a 3 year recruiting hitch here from 2006 to 2009, which made his Mom happy.

You are the second guy I have seen using Shadow chain. I use it on pedal side, and am in the midst of machining up
an improved making/assembly press tool. The Shadow brake and make tool is nice but on occasion fails to keep all the link plates parallel to press the pin through.
Tom
 
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wrenching4fun

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I use parts that happen to be in my parts bin, most of them left over from old projects. That's why I call this my Frankenstein bike, a chain from one bike, a sprocket from another, bits and pieces that I'd never use on something else. After the hurricane I was tempted to just chuck this stuff in the dumpster, but now I'm glad I didn't. What are you working on, other than your chain press?
 

wrenching4fun

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It seems like fabricating is the hardest part of this hobby. I just made an adapter plate to rotate the exhaust I purchased from AGK so the muffler tucks under the frame and out of the way instead of hanging off just inside the left leg. Speaking of the AGK muffler, when I took the bike out for a spin today it ran okay, but seemed to bog down after half throttle. The Predator has AGK's 19mm carb and intake, and the pipe and muffler they sell for Predy 79s. If you look at the outlet on the muffler it seems pretty small compared to the diameter of the header pipe. Could that be my problem? I didn't tune the carb, assuming it was already set up for the Predator.
 

Tom from Rubicon

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Apr 4, 2016
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So far my Sportsman Flyer 80 has functioned well, but now I have installed a new engine that I did the Port, Polish, and 50 thou. head deck. Everything else is how it was. Clone 19mm Mikuni fitted to a S.F. intake manifold. I had FFV8 laser me a exhaust manifold flange and one of his 90degree exhaust tubes, the tube was cut down to a two inch stub. Got a buddy at work to TIG it together for me . All larger than the head port size so flow was never in question. So I fitted 1" I.D. SS flex tubing to the exhaust stub with a custom made by me clamp. Down stream a 3/4" Briggs muffler stub fitting slips into 1" I.D. tube.
Custom clamps made by me too, 14ga. steel with industrial black oxide finish. Only back pressure is the F'n muff.
Carb needle clip in middle groove. I only got in the shop for two beers today, so the custom chain maker is slotted, drilled , and tapped for the closing screws. A few photos (they are also in my two threads).
Tom
 

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Tom from Rubicon

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Apr 4, 2016
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Rubicon, Wisconsin
The photos of your shop and your build, post apocalyptical hurricane, in the order it is in! Recovery is an understatement.

I like chopper builds, but in S.E. Wisconsin, home of Harley. Police are particular about what gets a pass.
Tom
 
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wrenching4fun

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I hear ya, Tom. Nice work on your Sportsman. It certainly would stand out in a pack of hogs! Although I rode Harleys for several years, I'm more fond of light, nimble motorbikes. I have a Sachs 2-stroker that I rode for fun and used the Harley for touring. Our cops are pretty laid back here in Eastern NC where we have the youngest sheriff in the country. When I was riding my Whizzer, they would stop me just to look at it and tell me about their grandpa who rode one during WWII when cars weren't available and gasoline was rationed. Should have held onto that Whizzer, but you can't own them all! When do you expect to have the Sportsman on the road? Might reach out for help souping up the Predy.
 

Tom from Rubicon

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When do you expect to have the Sportsman on the road?
Soon I hope (Christian Name Missing), as we are now in peak riding weather. And the Hot Rod engine needs proving.
I should have had a Whizzer.
They are the bug that bit me back in the 80's.
Mona and I were on a country cruise 60mi West of Chicago, ILL.
Aboard my mount that I had then, and still do a R80/7 BMW. Pack of old to me dudes were heading the other way.
Riding on these weird engine powered Schwinn's. We turned around and got the pack to stop for a visit.
That is how i met Whizzers, and wanted one. Fast forward 2016 dude at work rolls up with an engine powered bicycle.
That is why I built a huasheng huffy davidson which was fun. But then it was why go cheap? A cousin once asked.
"Why do you always have to have the best?" My reply. "Why settle for less". That is how I came to Sportsman Flyer.
You can see what I did for my engine here. Starts at 49. In the mean time I hope you resolve your exhaust restriction.
Port and polish ain't gunna fix that.
I get the Flyer running by the weekend if I stop fooling around and I really need a ride.
Photo of the Shadow chain maker. The main channel fits the link width precisely, creating precise link plate alignment.
Tom
DSCN0033.JPG
 

wrenching4fun

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True to the Frankenstein nature of this bike, I got the exhaust right by mixing parts. Used the aluminum flange from AGK and a one inch pipe I had forgotten about in a box. Had to drive a socket in one end with a ballpeen hammer for a joint. Ended up using the smaller half-inch screw-in muffler that is good, if I recall, for up to 5 horse engines. BTW, what do you estimate the HP of your engine with all the mods? I can't get a handle on HP ratings. These 79cc Predators start life at 3 horses which seems low since my wife's 50cc Yamaha Vino is rated at 11. Can't recall what the Whizzer was, but it pulled like a John Deere. More mysteries to ponder. Better pictures of Frankenstein after my ride tomorrow.
 

Tom from Rubicon

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#25 Has you posting a self diagnosed exhaust restriction. Self inflicted. It is. Using salvage is commendable, but a restricted exhaust system, ya get what ya got. The top advertised hp of the Whizzer engine in 1949 was 3hp.

AGK and ARC Racing both quote 5 to 7hp out of a 79cc engine. Both spec. Port, Polish, 50Thou head deck, 19mm carb and ARC racing 28 degree advance billet flywheel.
The hp of my un modified 79cc predy with the 19mm carb got this heavy bike near 40 in the flat.
Tom
 

Tom from Rubicon

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Tom, when you test the Sportsman with the modified engine, please give us a comparison. What's everyone's experience with reliability after the mods and what is the advantage of a $165.00 billet flywheel over stock other than weight?
The test results such as they will be. I intend to publish my (impression) empirically. I got an Esker that taxed the 3hp
stock Predy. bigly and on lesser inclines I would like to accelerate up from a stop light. We will see.
If you read my threads I would not have to repeat myself. But you ask about justification of the use of a ARC flywheel.
I talked to Shane at AGK, he said ungoverned 79cc predy flywheels in his experience have never failed. Empirical data.
There is a you tube of a flywheel failure. The magnet mounted as they all are retained with one 5mm screw. let loose.

ARC billet flywheels have epoxy encapsulated rare earth magnets and counterweights also encapsulated. Maybe the most important performance difference between stock cast iron flywheel and ARC's flywheel is the ability to adjust spark timing.
I weighed both flywheels on my grandpa's scale in case there was a weight some difference. They were the same.
I have not found Predator spark advance info. A keyed ARC flywheel states 28degree advance and going keyless, spark can be advanced more.
Take your time to sort through this thread. Adventures and misadventures.
(60) 79cc Sportsman Flyer build | Motorized Bicycle Engine Kit Forum (motorbicycling.com)
Tom
 

wrenching4fun

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It’s been a while since I’ve posted because I’ve practically redesigned the entire build. Some of the changes came out pretty well and I thought you might be interested. Before I get into the details let me mention that the photos aren’t the best. What’s left of Henri has been dumping rain off and on, so I had to take the photos from the garage.

First, I wasn’t happy with the fitting of the engine in the frame. It was too high in the rear, creating clearance issues with the spark plug, and too low in the front. Because of the angle of the frame’s top bar I had to move the engine forward to raise it. In order to do that I had to redesign the front engine mount which moved it forward about 2 ¼ inches. Here are pictures of the original front mount versus the modified one. The new mount tightens with 10mm lock nuts on hardened bolts.
 

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wrenching4fun

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Second, I installed a larger primary drive sprocket to give me better acceleration and to eliminate some vibration. Of course that required a longer chain and a redesign of the chain guard. As I mentioned in a previous post, the centrifugal clutch was made from simple brackets bolted to the face of the engine and the original steel muffler guard for the Predator. I’ve never been a fan of tensioners, so I slotted the engine mounting plate and made a screw-in adjuster that pushes the base of the engine forward to tighten the chain. The slots are about an inch long which gives me plenty of adjustment between links of the #41 chain needed to fit the Hilliard heavy duty clutch.
 

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wrenching4fun

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The previous changes freed up space behind the engine and beneath the seat to relocate the tool box and the electrical box that holds the key switch, the rectifier, the regulator, and a fuse, all connected together via universal 16 post insulated wiring panel mounted to the box lid. When I raise the lid all of the connections are exposed for easy troubleshooting. A simple wiring harness runs from the magneto to the rectifier, then another runs from the DC output of the rectifier to the lights. The boxes and brackets aren’t painted black yet because of the rain. I installed a small sealed lead acid 6 volt 4ah battery to even out the current and provide lights when the engine isn’t running. My Whizzer was designed the same way making it easy to troubleshoot electrical problems. I replaced the bulky moped light switch on the left hand bar with a toggle switch on the top of the headlight housing like vintage British bikes. The switch allows me to turn the lights off if I need a quick charge on the battery. When I drilled the hole for the switch I found that the housing is chrome plated brass. It was originally a spotlight from a 30-something car I found at a junk shop.
 

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wrenching4fun

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Next, since I changed the gearing on the primary drive, I had to compensate on the secondary drive from the jackshaft. Instead of installing a larger fixed gear, I put in a freewheel so the primary chain doesn’t turn when I’m coasting. I found in my parts bin an aluminum hub threaded for a freewheel with a 5/8 bore that fit the jackshaft. It turned out well because the larger freewheel increased the clearance between the size 415 secondary chain and the frame which was uncomfortably close. Again, to eliminate the need for a tensioner I slotted the rear wheel dropouts and installed moped chain adjusters, also from my parts bin.
 

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Tom from Rubicon

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My engine now takes 1/2 - 3/4 throttle cold. Still not responding to WOT. But with the .039 jet, it runs much better. Guess I'll drill the jet to .043 and see what happens. It has been suggested to go to a higher tooth drive sprocket. Currently a 44T. I'll see if a local supplier has a 46T.

Tom
 
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wrenching4fun

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Did you get your carb sorted out, Tom? Is it possible your timing jumped? I took note of your point on a restricted exhaust and swapped my muffler for the larger one. The Predator likes it much better.
 
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Tom from Rubicon

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You can't jump time. but it is easy enough to misalign marks. Didn't do that
Turns out I had a gas flow restriction that I never paid mind to before. Been going on since day one I suppose.
When y'all have some time read and laugh.. (141) 79cc Sportsman Flyer build | Motorized Bicycle Engine Kit Forum (motorbicycling.com)
I got another thread started about what gets done in my machine shop.

Fella convinced me to abandon petcocks and run a sediment bowl instead. Tomorrow I will find out.
Got this one plumbed in. Amazon.com: Briggs & Stratton 690612 Fuel Filter, Glass Sediment Bowl and Fuel Filter Assembly : Automotive
photo of my exhaust
Tom
 

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