Frame Rebuild for 212 Engine

Discussion in 'Board Trackers and Vintage Motorized Bicycles' started by Gbrebes, Aug 13, 2016.

  1. Gbrebes

    Gbrebes Active Member

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    Hey Everybody,

    I built this bike going on 5 years ago now and I first ran it with a 5 horsepower briggs engine, then a Honda GC 190, then back to a built briggs raptor for the Socal Motorized Bicycle races, and using the GC 190 on the street. I have wrecked at least 4 of these GC 190 engines, sometimes snapped valves, sometimes scored cylinders, and lastly I threw a rod a couple of weeks ago. I decided I can't take it anymore.

    I have been contemplating rebuilding this bike for a Predator 212cc engine for a couple of years and now it is finally time.

    Gilbert
     

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    #1 Gbrebes, Aug 13, 2016
    Last edited: Aug 13, 2016
  2. Gbrebes

    Gbrebes Active Member

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    It took me most of one day to tear the bike down. I then cut the frame above the points where the previous motor mount sat. After the cut, I placed the engine in the space and figured out I needed to drop the mount about two inches.

    I then bent 1 1/8" pipe for the new drop loop using 3/4" EMT manual conduit bender from Home Depot. The tubing does deform/flatten out at the bends, so I then squeeze the tubing on the wide sides in a vise to bring it back to reasonably round.

    I had to fill the old hole in the bottom bracket for the downtube and re-drill a new hole more towards the bottom of the bottom bracket.

    Here is the frame with the new drop loop, and one with the motor laying in the space.

    The two splice points have an internal lug. I then added an external sleeve to the front frame splice, and two more sleeves where the new mounting plate will rest.

    Still to come, a vertical gusset under the mount and two gussets welded to the seatpost member, bottom bracket, and underneath the motor mount plate.

    I will keep you all posted with progress.

    Gilbert
     

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    #2 Gbrebes, Aug 13, 2016
    Last edited: Aug 14, 2016
  3. indian22

    indian22 Well-Known Member

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    Looks like you're going in the right direction. Rick C.
     
  4. FFV8

    FFV8 New Member

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    Outstanding Gilbert!

    Nice work as always.

    We blew up a couple of those GC's as well & moved on too. Dropped valves both times.
     
  5. Harold_B

    Harold_B Active Member

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    Great looking bike. Thanks for the detail pics on the welds (I'm a newbie with a wire welder and I'm always looking for good examples of work). Looking forward to seeing what you're going to do with gussets. Any chance you have an original build thread for this that you could link to?
     
  6. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    Hi Gilbert
    To race in the 8 HP Midrange class the Predator 212cc engine can
    only have very few modifications.
    It doesn't take much for a 6.5 HP governed motor to make 8 HP

    Grant #27 will not be racing his 14 odd HP Predator in the Midrange
    on Oct 22nd at Grange Motor Circuit. He also has an Unlimited 212cc.

    Or maybe you are intending to go all out and race Scotto in the
    Unlimited class? .wee.

    We used to have a 11.99 HP class that raced with the Unlimited but
    pretty much everyone migrated down to the Midrange class.

    A 212cc / 200cc with a few cheap mods is a very affordable racing engine.
    What clutch are you planning on using?

    Lance has built a big bore GX 200 to race Scotto.

    [​IMG]
     
  7. Tony01

    Tony01 Well-Known Member

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    Nice. I would (and will) cut off the right side gas tank mount, and have a mount only on the left side gas tank mount and will soon have a heim joint higher up. You never know if that gas tank mount will take a piece out of the crankcase in a crash. Using the 4-point engine mount with just one tab for the left side gas tank mount is enough to keep engine movement to a minimum (I know by the sound... there is only .030" frame clearance from valve cover..). Add a joint up at the cylinder head or at the boss middle of cylinder for the shroud and you'll be golden.
     
  8. Gbrebes

    Gbrebes Active Member

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    Thanks guys,

    Harold, here is a link to the original build thread. It's a misleading title, as I ended up using a women's JC Higgins frame as the donor. I am an amateur welder also, that's why I decided to use brazing instead, it seems more forgiving.

    Watch out, that build thread is unbearably long.

    Hey Neil, I am aware of the mid-range rules regarding the 212. I was planning on having two engines for this bike, one race, one street. Oddly, the race motor will be the least built. I was planning on taking out govenor, 18 lb. springs, billet flywheel, stock carb with aftermarket air cleaner, and straight pipe exhaust. Please let me know if the rules have changed, I plan to be in compliance, and I also am planning on taking the side cover and valve cover off to show what's inside the morning before the race.

    Or maybe I could try to race Scotto with my street engine, but I got to ride scotto's bike, and I don't think I want to go that fast. Kind of scary.

    Hopefully have more updates by tomorrow.

    Gilbert
     
  9. Harold_B

    Harold_B Active Member

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    Thanks for the link Gilbert. I could have searched but was feeling lazy for some reason. It will be nice for anyone interested to have it here on the first page though. I just read it beginning to end again (I had read it when it was current) and there's so much great content/information there. You did a great job documenting your build. What an awesome bike. I think it's cool that you have found a way to get your two wheel fix and reach a compromise with your SO. Priorities in life. It's been a while since I've brazed anything like maybe 40 years so I'll probably hang with the stick welder for now. The brazed joints sure look good though. Good luck on the 212.
     
  10. Gbrebes

    Gbrebes Active Member

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    I got less done this weekend than I had planned. Just could not get enough hours in "the Shack". I cut and shaped the motor mount and then cut the slots for the mount bolts, picture one. I then cut and shaped the vertical gusset between the downtube and the bottom of the motor mount, picture two.

    Picture three is the mount brazed in to fit.
     

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  11. Gbrebes

    Gbrebes Active Member

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    I then moved on to the vertical gussets. Picture one is the cardboard template.

    Picture two is the rough cutting of the gusset outline, I used 3/16" plate for the gussets and the motor mount.

    Picture three is the finished metal piece.

    And picture four is the gusset sitting in place. It may seem like overkill with the gussets, but I respect the torque and torsion of this engine, and my frame once cracked right between the bottom bracket and the rear junction of the motor mount in the past, so I figured better overbuilt than under built.

    I am counting on the power of this engine to overcome all the weight I am adding to this frame.

    So i got the gussets fit, but still have to braze them in place. I will then move onto the "sled" motor mount idea I stole from Culver City Classics. I want to be able to adjust the motor a couple of inches forwards and backwards to get proper adjustment for my CVT belt, so I am building an angled motor mount that bolts to the engine mounts, but also slides on the horizontal frame mount with four additional mounting bolts. Pictures to come.


    Gilbert
     

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    #10 Gbrebes, Aug 15, 2016
    Last edited: Aug 15, 2016
  12. Gbrebes

    Gbrebes Active Member

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    Hey Tony,

    I have been wondering about this. So you think just one of the gas tank mounts is enough? I was planning to incorporate them into my lower engine mount, but I am also contemplating adding some sheet metal to the case where the oil sensor is to round off the case to make it look a little more vintagey.

    Thanks,

    Gilbert
     
  13. Gbrebes

    Gbrebes Active Member

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    Hey Everybody,

    Some update pictures. I finished the frame modifications and have now moved to the three different motor mounts. First, I built an angled "sled" mount to bolt the engine to, but then it slides on the frame mount to allow for primary belt tension adjustment. I call it the CCC sled, because I copied it from an old build done by Culvercityclassics. I then made a new bracket that I welded to the frame to accommodate mounting to one of the gas tank brackets and finally made a bracket that bolts via the front head bolts and then to a frame bracket. Also a picture of the engine with its new flywheel. I also eliminated the governor and oil level sensor, tapped and plugged those holes and put in 18b. springs for the valves. Lastly, I copied CCC again and added the brass fill plug to the case, as well as a brass plug for the lower fill hole.

    I am currently modifying my forks by adding an extra leaf spring. I will then be ready to re-assemble and then move onto fabricating the exhaust and intake pipes. Hopefully I will be on the road in a couple of weeks.

    Gilbert
     

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  14. Gbrebes

    Gbrebes Active Member

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    More pics of what I described earlier.
     

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    #13 Gbrebes, Aug 25, 2016
    Last edited: Aug 25, 2016
  15. Tony01

    Tony01 Well-Known Member

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    Yep rounding it off would definitely look cool. I think just the one support on the left is best for two reasons: one is its the drive side, and two, it's a lot closer to center than the right side. 5 points for me for right now but soon I will add the additional support on the front of the cylinder.

    looking good :D
     
  16. Gbrebes

    Gbrebes Active Member

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    Hey Again,

    Got the bike back together in preparation for making an exhaust pipe and a new intake pipe. I also added an extra leaf to my front fork to stiffen the suspension, bringing the total to three leaves, featuring my home made leaf spring straps. I look forward to trying the new suspension out on the road.

    To me, the bike looks about the same. The engine looks pretty small in the frame cavity, not much different than the old Honda GC190. The drop loop is 2 inches lower, but it doesn't really seem that much different.

    I also sprung for an imported Lepper Primus 5 spring seat. I am hoping it provides more travel in seat suspension over my vintage long spring Persons-style seat. I am not sure what I think about it, it sits a little bit high, and the seat pan is actually smaller than my vintage saddle.

    Hope to start on the intake and exhaust pipe later this week.

    Gilbert
     

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    #15 Gbrebes, Aug 26, 2016
    Last edited: Aug 26, 2016
  17. indian22

    indian22 Well-Known Member

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    Turned out great Gilbert, look forward to the new additions of exhaust & intake. If you're bothered by open air in the loop frame some "crank case plates" would fill in the bottom of the loop...I think the addition of exhaust & induction system will fill in the rest, it's a really cool bike that will draw a lot of admiration on the street or just sitting at your favorite stops. Rick C.
     
  18. Gbrebes

    Gbrebes Active Member

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    Started working on the intake. Cut the flanges and hand bent some 1" tubing. It came out pretty lumpy, but I'm too lazy to make a brand new one. I am thinking of buying mandrel bent elbows at a later date.

    Using the stock carb for racing regulations in the mid-range class of the Socal Motorized Bicycle Races will make the build a little more complicated. I have a 22mm mikuni that would just bolt on and go, but for this carb I have to fabricate an arm to attach to the throttle post, then add an adjustable cable stop to the intake pipe, as well as add a return spring. Haven't finished this throttle linkage part yet.

    Pictures of home made intake, and home made filter flange that bolts to the carb. I used a 1 1/2" plumbing pipe cap for the flange. And then a pic of the velocity stack installed on the filter flange.

    Slow progress, but some progress,

    Gilbert
     

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    #17 Gbrebes, Sep 3, 2016
    Last edited: Sep 3, 2016
  19. MotoMagz

    MotoMagz Well-Known Member

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    Great rebuild ,I've said it a few time love this bike. What can you tell me about the fly wheel? Wish I could do fenders on my bike ...maybe on my Whizzer build.
     
  20. Gbrebes

    Gbrebes Active Member

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    Hey MotoMagz,

    The flywheel is an ARC Racing billet aluminum adjustable flywheel with a smaller circumference.

    It is to me basically the same as the flywheel I use on my briggs racing engine. It is smaller (the size of a 3hp briggs) so its supposed to spin up faster, and you need a small bracket for the coil to get it closer to the flywheel. They basically took the briggs adjustable flywheel and changed out the middle part to match the taper of a 212 predator engine.

    The aluminum part of the flywheel can spin on the black metal hub after you loosen the six bolts holding it together, thus changing the position of the magnet and advancing the timing of the engine.

    When it is at the end of its negative range, that is stock timing of 25 degrees. It has a range of 14 degrees, so that's 25 - 39 degrees adjustment available. I have not started the engine yet, so I still have it at stock.

    Unfortunately for hemi predator owners, this particular flywheel is not available, I do not understand why.

    In regards to mounting fenders, you could always add brackets to the frame to make that possible, but I see that your frame is already painted, so a re-paint would then be necessary.

    Gilbert
     
  21. MotoMagz

    MotoMagz Well-Known Member

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    Ok I do like the adjustability of the flywheel. My timing is advanced to 32 I believe and when you rope start it it will lift the bike right off the ground. Or drag your arm to the ground! But finally after some research I can wrap rope then pull slow to get past that completion stroke. Then pull the rest of way with no problem. My arm feels much better now! You will love this motor with a few mods gov. Removal,carb, and pipe. Then springs #18 springs if you can race with them or the carb. I'm wondering which carb you guys runI know It says Mikuni and it's a 22mm but is it the real Vm22-133?
     

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