212cc 2-speed Schwinn rebuild

Discussion in 'DIY Home Built Motorized Bicycle (non kit)' started by Tony01, Jul 26, 2016.

  1. Tony01

    Tony01 Member

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    Well I blew up my Briggs flathead, took it down a hill with too low a gear ratio and the connecting rod grenaded, even took a bite out of the plastic cam and put a huge crack in the front of the block. This was about 10 days ago. I searched for a briggs 5hp, but my buddy was swapping in a 212 and i wanted to keep up with him so...

    [​IMG]


    Bought a 212cc HF 69727 Predator motor (non hemi dished piston). Removed the governor.. man what a pain in the a$$ to take off that little clip that holds the governor gear. I had to completely rebuild the motor mount and 2-speed. My buddy gave me an 8' length of 4"x4" 1/8" wall box tubing and I got to work with a brand new 5-pack of HF cutoff grinder discs.

    Making the engine fit was easy, but there is only about 35 thousandths clearance between the valve cover and the double tubes. If I pound down the lettering on the valve cover I'll have a 3/32" clearance! When the motor isn't supported at the front the vibration causes it to hit the tubes. I added a small tab to support the left predator gas tank mount. My buddy made a Heim joint for his bike that connects the shroud mount up there to the downtube, and cut his gas tank mounts off completely citing a risk of breaking one along with putting a hole in the crankcase. I'll add a Heim joint pretty soon as well.

    The 2-speed took me about 40 hours. Hole saw, welder, drill, and angle grinder only. Spacing was difficult. The flange bearings eat up about a 1.25" of shaft space each. The final drive chain is a quarter inch out.. but its a long chain with the frame stretch and the rear sprocket is a 44t kit type that's only an eighth inch thick, so it takes it like a champ with the chain moving around on it. With the pedal chain sprocket limitation there just wasn't a way to get the final chain perfectly aligned. (LIGHTBULB! what if I put the bearing outside the... nah.. it would be too far out.. f*** it...) but it runs, and doesn't jump, and as long as it runs I really don't give a damn about it. The bearing mount bolts on the bottom JS are actually through-studs with nuts on the inside welded to the box tube, so tightening them down doesn't squash the box. Also welded in a little strap on the outside of the box to support it to further prevent bending in case the welds on the stud broke. Had to grind down my bolts for the upper jackshaft and cut relief holes and slots for the 2nd gear clutch and output sprocket.

    The frame was wire brushed to bare metal, sanded, and painted with rustoleum truck bed liner. Angle grinder wire wheels are serious stuff. I got bit many times. The finish is very strong, looks good, and is oil and gas resistant.

    I made my own flanges from 1" OSH washers (the thick ones!! .190" not the .150" thick ones that come in the same batch!!) and used 1" OD fork parts for both the intake and exhaust. Exhaust was done by cutting pieces with angles and welding them all together for the curves.. it looks like boogers in the corner of the underside of a church pew so I wrapped it up. All I got here is flux core! I also got a welding tan from welding with my shirt off in 90 degree weather.... complete with helmet tan line...

    My first gear is 9.3 and my top gear is 6.4. This is approx a 1.45 jump. A 1.45 to 1.5 jump is perfect in my opinion. I have put about 3000 miles on the old 2-speed with a 1.6 jump and while it worked; it was way too much and caused excessive clutch wear, even with throttle blipping on shift. It's much nicer to keep your engine in the power band when it shifts. The top gear of 6.4 is way too damn tall though, but it's all I had for sprockets and I didn't want to gear it too low at 7.7 for fear of over-revving the 212. Tomorrow or another day I'll go down to Grainger and get a smaller output sprocket to get the ratio to a 7:1, will still be pretty tall but better suited I think!

    The predator engine is very fat with the shroud and all, so I decided to go with a rope start like I had on the briggs. Anybody considering this should note that you must cut down the plastic fan down to the diameter of the starter cup and use it; otherwise the rope gets stuck in the gap between the cup and the flywheel. I also shortened the cup by taking it just down to the edge of where the slots would be. It really narrows the predator engine down.

    The carburetor is a PZ19 slide type Keihin clone. Works real nice and engine idles very smooth! Needs some tuning, have the needed on max fuel setting for the midrange (lowest clip position). Still have some small things to figure out, like getting matching bolts here and there, putting the license plate back on, etc.

    I just rode my first 15 miles for break-in motoman style and MAN does this thing haul. Was passing cars that were doing 45-50.

    I'm surprised nothing broke or fell off on my first 212 adventure. Guess I finally figured out how to build 4-strokes...
     

    Attached Files:

  2. msrfan

    msrfan Active Member

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    Nice job Tony. Looks bullet proof. I love that Powerglide effect when it shifts under power.
     
  3. Tony01

    Tony01 Member

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    Thanks Dale! Starting it cold
    https://m.youtube.com/watch?v=AuH3iNGh5DY

    Yep the shift is nice. It wears the clutch faster though. When I feel it complaining a bit right before the shift I blip the throttle to take the load off and let the clutch lockup without slipping too much. Depending on throttle input you can have an early or late shift too.
     
  4. scratchbuilder

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    Your frame is what id like to build. I like the low..2feet on the ground when you stop. Gotta go have a look at a 212. See if it looks too big for me to say..."naw Sir, its only a 4hp, officer. I'm thinking a mm like Gilbert did. Like the acoholic says.."I can stop building anytime"
     
  5. Tony01

    Tony01 Member

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    This build is always under construction. Since the rebuild in July, I've done a number of things:

    Made a new exhaust header. tubing is 1" ID, flange is 3/8" thick, and the brace tab is 3/16" thick. The inside of the pipe was ground and sanded smooth to 320 before welding each successive piece. ~9hrs

    [​IMG]thumb_IMG_2505_1024 by Tony K, on Flickr

    I didn't wanna wrap it, I thought it was so pretty

    [​IMG]thumb_IMG_2509_1024 by Tony K, on Flickr


    Also fixed my intake manifold and adapted it for the stock predator carburetor, because it was bending too much and causing air leaks. Increased thickness from .120" to 5/16". Port matched to engine!

    [​IMG]thumb_IMG_2541_1024 by Tony K, on Flickr

    [​IMG]intake flange by Tony K, on Flickr

    [​IMG]thumb_IMG_2416_1024 by Tony K, on Flickr
     
  6. Tony01

    Tony01 Member

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    Modified the carburetor to have an adjustable main jet. Did this by drilling out the stock jet to approx .055", and modifying a Tecumseh adjustable jet so that the adjusting needle screws all the way down to bottom out on the jet, and not on the bowl nut. This involves drilling inside, re-tapping a few threads, turning back the bowl nut head (I chucked it in a drill, turned it on, and used an angle grinder to turn it down, but a lathe is best of course).

    Works great!

    [​IMG]212 adjustable jet mod by Tony K, on Flickr

    [​IMG]mod vs stock TEC adj jet bowl nut by Tony K, on Flickr

    [​IMG]clamping fixture and bigger hole in stock 212 jet by Tony K, on Flickr


    This is where the needle normally bottoms out. The stock bowl nut must be shortened down to approx .040" away from the smaller diameter, then the small bore must be drilled out and tapped a few threads same as the other ones, because the end of it must be bored down to allow the needle to screw further into the bowl nut. Best done on a lathe but I did it with hand tools.
    [​IMG]bowl nut cross section by Tony K, on Flickr

    [​IMG]completed adj jet mod by Tony K, on Flickr
     
  7. Tony01

    Tony01 Member

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    Braced the rear end with 1" C-channel for the chain stays, 3/4" box tube cut lengthwise for the seat stays, and 1/8" steel for gussets.

    Put new tires. CST Cyclops 26x2.4. I only have 500mi on them so far but I really like them.

    seat stays separated as i was bending the box tube in, so I welded the entire area up.

    [​IMG]weak area by Tony K, on Flickr

    Just bent the c-channel over my knee while fitting and grinding.

    [​IMG]1" C-channel chain stays by Tony K, on Flickr

    [​IMG]nice flux core welds by Tony K, on Flickr

    [​IMG]painting rear end by Tony K, on Flickr

    made a tab for the brake reaction arm that bolts onto the gusset.
    [​IMG]rear gusset by Tony K, on Flickr
     
  8. Tony01

    Tony01 Member

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    Setup a brake light using a magnetic switch. It's tricky to mount on a lightweight hydraulic MTB brake lever, but I figured it out. The magnets are epoxied to the lever, and wrapped with some window screen also epoxied in for strength. A 450ohm resistor was the best one for me.

    Everything is wired with frame as ground. Only one wire goes to the taillight. The on/off switch turns on the headlight, and the taillight in series with a 450ohm resistor and a diode. The brake light switch is wired to +12V and the taillight switch, so it works for day (off pos) riding. The diode in series with the resistor is what prevents the headlight turning on during the day when I hit the brake.

    [​IMG]magnetic brake light switch by Tony K, on Flickr

    Unfortunately my dash is not lit.

    [​IMG]dashboard by Tony K, on Flickr

    headlight is awesome!

    [​IMG]autozone $30 round light by Tony K, on Flickr

    This build is my daily driver and I need to be able to ride it in any California weather. This usually means heavy winter rains. I've ridden without fenders and it's only 5 minutes before you're soaking wet on all sides. Fenders are a must. I ride in the pouring rain all the time now if I feel like it.

    I used bairdco's instructions on how to mount fenders from his thread (thank you sir!) Used the same heat shrink tubing. Had to make my own fork mounts as I have a QR axle on the front. Made fender tabs, fork mounts, and annealed them with propane so they hopefully won't crack. The fork center mount tab attaches to the steerer on both sides, and the fenders are rubber mounted on every point. So far so good. Love riding in the rain now, just gotta figure out how to stop my visor fogging up.

    Also installed this glass pack straight-through muffler I got from a motorcycle dirt track machine shop I applied at. This muffler is really, really BAD A$$. Super quiet but when you open it up man does the engine sound off! Way better than an open header. I'm now a glass pack man. Welded a section of the c-channel at an angle to the seat stay to provide a mount for the muffler with a section of 1/4" rubber.

    [​IMG]glasspack mount by Tony K, on Flickr

    The bike is an absolute joy to ride now. I feel much safer having a brake light and better about going out in uncertain weather. It looks better, too. I routed all the wires together. The brake light wire runs with the drum brake cable and the tach and kill switch run with the throttle cable.

    [​IMG]with glasspack by Tony K, on Flickr
     
  9. Tony01

    Tony01 Member

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    But, there's trouble. My 2-speed top gear chain has eaten up my sprockets. I think I know why people use #35 chain. because the sprockets are bigger for the same diameter making the chain flex less per link. In the meantime I've swapped the bike to single speed with a single jackshaft. Although I really miss and prefer my 2-speed, I do love the simplicity of a single that I've not felt in a long time. The gearing is 7:1 and the clutch is starting to get worn out, running a black spring with mixed heavy/regular shoes. I'm probably going to swap to either all heavy/black, or all regular/green.

    My 2-speed clutch looks real bad on the sprocket and the bell is worn deep after thousands of miles of shifts, but the bronze bushing still looks good. I guess the oiling every hour was too much maybe, but who knows. Most of my shifts were easy. I would blip the throttle when the clutch would start chattering. I figured it would save it somewhat. Guess it did on the bell. I could probably use the bell for another couple thousand miles, although it is really worn a lot along with the shoes.

    [​IMG]tired sprocket by Tony K, on Flickr

    [​IMG]2nd gear clutch 4000mi by Tony K, on Flickr

    [​IMG]keyway of death by Tony K, on Flickr

    The next bike modification is to drop the engine down over the bolts that hold the aluminum seat tube clamps together. I ordered and received some flathead allen bolts, 3/8" 3" long, and what do you know, I don't even have a countersink big enough to make them work. I plan to countersink the engine mount plate and then slide the engine right over em. I should gain an inch of valve cover clearance so that i can adjust the valves with the engine in the bike.

    [​IMG]engine clearance by Tony K, on Flickr

    I'll also completely remove the gas tank mounts (I've been using the drive side one) and will make a mount on the down-tube using an old 1" gooseneck.

    [​IMG]right side by Tony K, on Flickr

    see my other thread for the trailer I'm building!
     
  10. Ludwig II

    Ludwig II Well-Known Member

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    You do realise you've created a motorcycle with the same style as some early 1950s Japanese types?

    [​IMG]

    1952 98cc Minato Health

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    Tohatsu TFL-80

    [​IMG]

    [​IMG]
     
    #10 Ludwig II, Dec 18, 2016
    Last edited: Dec 21, 2016
  11. ultralight01

    ultralight01 New Member

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    I love this bike, it's another inspiration for my build. Although I'd like to keep the pull start on. I wonder if it's possible to add your own sprocket to the flywheel and make a homemade electric start? Because it definitely takes a good 2-3" out of the width of the engine.
     
  12. dogcatcher

    dogcatcher Member

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    This one could easily become a dream of mine. I really like the looks of it,
     
  13. scratchbuilder

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    I like what you have done. Especially the shape of the rear triangle, the way the chain stays sweep down low. You mentioned ridin single speed for now. Can you cruise at 30 with low rpm's??
     
  14. Tony01

    Tony01 Member

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    Thanks for the comments guys!!

    Scratch yeah I can cruise low rpms down to around 25. Right now the clutch and shoes are worn so it's engaging and disengaging a bit higher at 30ish. But you know even with the 2-speed I could cruise at 25 in high gear. Cause on heavy acceleration it could shift at 35, but then with light loads and keeping light power on it I could keep the top gear engaged almost down to 25ish but it would start slipping. 30mph top gear cruise was the best.

    I think I'm gonna swap the high gear box and primary chains to #35. This will fix my 2-speed and hopefully reduce the amount of maintenance it needs while I work on other 2-speed designs. I'll be starting this other build soon probably with a Briggs 5hp and will use it to test new designs. I wanna create a 2-speed jackshaft for motorized bikes, because the ones available are for minibikes and don't have the right ratios, adjustability or shift speed.

    [​IMG]81 Schwinn by Tony K

    This bike was stretched to look like mine! The chainstays are straight though.
     
    #14 Tony01, Dec 20, 2016
    Last edited: Dec 20, 2016
  15. msrfan

    msrfan Active Member

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    Yeah Tony, I always wanted to make a high quality 2 speed with good go kart clutches, but it wasn't very cost effective. I've even thought of a 3D Motorsports hand clutch for low gear and a good go kart centrifugal clutch for high gear override. Maybe use half-link chain for more adjustability. You could even start with a cent. clutch for low and engage the hand clutch for high. I have lots of weird thoughts, but it may give someone ideas. A planetary would be the most compact.
     
  16. scratchbuilder

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    Awlright, 01 building again! From the looks of your parts, with an igh one shift not done in sync would fubar the mech with a 212. Looking forward to your trans plans.
     
  17. Absorbed

    Absorbed New Member

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    Hey I'm currently doing a 212cc Hf build myself. Having a problem finding a good enough bike frame to put it in.... any suggestions on what frame would fit, in a decent price range....
     
  18. malatious

    malatious Member

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    When I was a teenager, I scavenge a 2 speed gear box off of an old Cushman my uncle had laying around and put it on my mini bike. It had one chain from the clutch and one down to the rear sprocket. It had a suicide type shift lever. That gear box was bullet proof and really worked good. I don't remember it being any bigger than some of the Jack shaft setups I've seen. I would love to find something like that to use on one of these bikes, but hav'nt really seen anything like it since. With a 5 HP Briggs, in low I could get up any hill I wanted, and in high, my mini bike went around 35 mph, that was with 16" tires, and have no idea what the actual gear ratio was.
     
  19. Tony01

    Tony01 Member

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    Old schwinn works great long as you don't modify the frame with any stretching.. which is what caused both of my frame cracks I'm sure. Stretch it and it needs bracing. Also good, newer American cruiser frames with thicker frame tubes and dropouts are great too. Steel only (magnet sticks).




    Well the noise under the valve cover got to be really bad and I decided to open it up and see. Also, since I am removing the motor, I'll be modifying my engine mount to drop the engine down approx 1" so that I can remove the valve cover without removing the engine in the frame. I'll be replacing the hex head bolts with flathead allen bolts so that I can bolt the blocks and mount plate to frame, then slide the motor right over them and bolt it in.

    [​IMG]Untitled by Tony K, on Flickr

    I took the motor out and found that my valve lash had worn out to at least .010" on both valves. So I was losing a very large amount of duration and probably wearing the cam too.

    I was pleased to find the cylinder bore in perfect shape even after at least 100 hours of runtime. These engines might be cheap, but they are awesome!

    Specs: This predator is a non-hemi with an RTC-9 head. People say anything RTC-6 to 9 and you're golden. Well it's true. This thing comes stock with smooth ports and 27/25mm valves. I looked at another 212 I have with an RTC-2 head and that one only has 25/24mm valves and comes stock with a .045" fire ring gasket, whereas this one comes with the .010" gasket.

    This head also has automotive style split keepers on the valve retainers. I'm impressed!

    I figured while I had it apart, I had better port/polish it and shave it down... I took out the large bumps that ramp up to the valve guides, and even took the valve guides down some, and radiused the crap out of the inside corner on both sides, which had a huge sharp edge/burr.

    Before

    [​IMG]IMG_2969 by Tony K, on Flickr

    [​IMG]IMG_2970 by Tony K, on Flickr

    After

    [​IMG]IMG_2974 by Tony K, on Flickr

    [​IMG]IMG_2975 by Tony K, on Flickr
     
  20. Tony01

    Tony01 Member

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    Took the gas tank mounts off.

    [​IMG]IMG_2968 by Tony K, on Flickr

    Love the rain riding...

    [​IMG]IMG_2896 by Tony K, on Flickr

    Hopefully be riding this thing with high compression tomorrow...
     
    #20 Tony01, Jan 25, 2017
    Last edited: Jan 28, 2017

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