Skyhawk Frame up build

Discussion in 'Motorized Bicycle General Discussion' started by jerrywelz, Mar 11, 2016.

  1. jerrywelz

    jerrywelz New Member

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    Hello everyone! It's been quite a while since i've done anything motorized bicycle related. I decided to create a build thread to get some feedback and motivation. I've got a rolling frame right now and could use some advice. Here are some pictures. Please excuse the messy garage and cell phone quality. Just click the image to enlarge it.


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    Here is a quick mental list of what i still need, if anyone can think of anything to add that would be great.
    Seat and seatpost
    2 stroke engine
    Carb
    Exhaust
    Fuel filter
    Fuel line
    Fuel shutoff valve with correct threads for frame
    Crankset and pedals
    Rear Derailleur that will fit on this frame
    Drive Sprocket
    Brake handle
    Quality twist throttle
    brake, Derailleur, and throttle cables

    Im not sure about the rear Derailleur and the engine drive sprocket. Does anyone know what Derailleur works well with the skyhawk frame?

    The drive sprocket has got me stumped because i don't know of any adapters out there that will clamp to this sized wheel hub. In the picture i'm holding a caliper up to the hub and it appears to measure less then an inch. Is a rag joint mounted sprocket my only option?

    I'm Trying to get some momentum going here, but I don't want to rush or cut corners. My first motorized bicycle was heaps of fun, but it was always broken! I want to produce something more reliable this time around.

    Thanks everyone!
     
  2. Agreen

    Agreen Member

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    I haven't had any issues with my rag joint sprocket on my skyhawk frame. Then again, i use quality rims with thick spokes, so that may have something to do with the longevity.

    The seat post is supposedly a standard size now. I think it's 38.2mm?

    I recommend against getting a carb "upgrade". I wasted so much time and money looking for more power and speed, and ended up right where i started each time. Use the money for a good quality head and expansion pipe exhaust (not one of those cheap banana pipes).

    Can't help on the derailleur or sprocket adapter. I use a single speed bmx freewheel (with a 48cc engine, and it has enough power to never require pedaling)
     
  3. Cgk_iii

    Cgk_iii New Member

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    seat post size is 27.2mm, id recommend chopshopcustomz he makes really good quality solid steel seat posts and you can have it designed whichever way you would like!

    Why run a derailleur? Are you planning on running a shift kit or a jackshaft kit? If not id suggest replacing rear wheel with a HD coaster wheel. The standard size hub-sprocket adapter fits any standard coaster wheel, makes life a lot easier, also it adds an "emergency brake" if things get crazy hehe

    Look at the fuel shut off valves from SickBikeParts. I have one and am very happy with the quality, although im sure you can grab one from your local hardware store and have it work just the same.

    The bottom bracket is a standard size, 2" i believe. I reccomend running a BMX 3-piece bottom bracket, they have nice sealed bearings

    Performance twist throttle from sickbikeparts, they have a nice roller bearing pulley system

    Thats all ive got for now! good luck!
     
  4. MotoMagz

    MotoMagz Active Member

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    You can find a old school derailleur that mounts to the axle if frame has no tab.i had a hub adapter made for the same size hub years ago by Maniac Machanic. Good luck
     
  5. Agreen

    Agreen Member

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  6. ru14real

    ru14real Member

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    what size tires and rims are on that bike?
     
  7. jerrywelz

    jerrywelz New Member

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    The tires are Duro Slicks 26x2.125

    I'm not sure about the wheels. I ordered them from custommotoredbicycles.com and i know they are 26x2.125 with 12gauge spokes.
     
  8. jerrywelz

    jerrywelz New Member

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    Thanks for the tip on the derailleur. Yes i just ordered the manic mechanic adapter with his 2 piece reducer bushing and a 36 tooth sprocket. I prefer the simplicity of the single speed setup over a jack shaft.
     
  9. jerrywelz

    jerrywelz New Member

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    Thanks for the insight on the seat! I was looking at this Brooks B17 seat. I haven't ordered it yet because i'm still not sure i want to spend that much on a seat!

    http://www.amazon.com/gp/product/B0...ue&ref_=ox_sc_act_title_3&smid=A2RCT8MB1RT96V
     
  10. ru14real

    ru14real Member

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    damn those seats are expensive as **** and their not even that comfortable. why so much money?
     
  11. jerrywelz

    jerrywelz New Member

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    Well, they're made in england with genuine leather. I watched a few reviews that claimed they are quite comfortable. Anyway I went ahead and ordered one.
     
  12. ru14real

    ru14real Member

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    I was into racing and had a brooks saddle. It always chaffed my behind. i was using that stuff that made the leather softer and it did make the saddle softer, but it was and still is too uncomfortable for my liking. I think I paid something like 40 dollars in the 80s. Maybe I should sell it and get some motorized bike parts for my build.
     
  13. jerrywelz

    jerrywelz New Member

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    Got some parts in today! I installed the seat post and clamp for it. I also got the clutch and brake handles put on the bars. My engine came in! it's a 49cc 2 stroke. I really wanted to spend the cash on an arrow or crmachine (fred) engine with the balanced crank and ported head. Those engines run $300 minimum and this little 49cc only cost me $75. I went with the 49cc because I heard they actually can hit higher RPMs than the 80cc out of the box and they don't vibrate everything to **** @ WOT.

    Here is a progress picture!
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  14. jerrywelz

    jerrywelz New Member

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  15. jerrywelz

    jerrywelz New Member

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    Few more parts went on today, I got the screaming roo CDI and magneto coil installed. I also installed the fuel shutoff valve and plumbed the fuel line and filter. Installed a Shimano derailleur that comes with a hanger and works on this frame. Got my Brooks b17 seat in and bolted that up.

    Right now i'm waiting for the hub adapter inserts from Manic Mechanic, the chain-ring or sprocket (whatever you call it) and the cable to select gears on the derailleur.

    Im gonna have the bottom bracket and crank installed at the bicycle shop because i don't have the tools to do it right. After that i just need to fit the chains and ride! Probably gonna order an expansion chamber after April 1st. Should be up and running in a few weeks!

    ohh and a pic of course
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  16. Chaz

    Chaz Active Member

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    Very nice looking build, Jerry. That expansion chamber looks pretty good too. It seems like they thought it out well for fit and it's got the tab to bolt to the clutch cover. It wouldn't take too much work to run the pipe to the back and add a muffler.

    keep posting!
     
  17. tgaydos

    tgaydos New Member

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    looks like i'm going to have to do myself a solid and get a skyhawk frame for my third build, second build will be sold to fund this.

    very nice work man, the x-chamber looks a lot like the mid 80's yz80 pipes, you might give them a look as they can be had for cheaper.
     
  18. jerrywelz

    jerrywelz New Member

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    Thanks for the encouragement guys! I rode the bike today and realized a few things. The 49cc has no torque! The bike was struggling to pull me up a fairly steep hill with a 36t. The brooks b17 is not comfortable... i suppose my bottom will get used to it. I'm going to need an expansion chamber and some port work to make this thing more ride able.

    some pics!
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  19. ru14real

    ru14real Member

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    If you want torque then get a larger sprocket. The more teeth you have on it the more torque you will, the less teeth, the more speed you will have. about every tooth equeals about 1 mpg per hour. Maybe this gives you an idea to go with
     

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