The Walmart Special (Kent Fixie/Single Speed 700c)

Discussion in 'Photos & Bicycle Builds' started by BlueDestiny, Jan 1, 2015.

  1. BlueDestiny

    BlueDestiny New Member

    For this build I am using the Kent Fixie 700c, available from walmart for a cool one hundred bucks. I picked this frame due to its simple construction, consistent narrow tube diameter, wide pedal crank and low price. I initially wanted to buy a Thruster 700c (which is basically the exact same bike) but there were none available. Another deciding factor for this frame were numerous successful motorizing projects that I found via google and youtube. The bike I got was kind of sloppy (misaligned wheels, crooked brake pads, slightly crooked handlebars) but all those can be fixed pretty easily.

    3-4ths profile.jpg
    Not bad looking at a glance but a closer inspection reveals pretty humble components. Love the red tires though!

    front profile.jpg
    The bike has a very narrow profile due to the short handlebars. I'll definitely be careful on turns with this thing.

    rear hub detail.jpg
    The rear hub with a single-speed gear and fixie gear. The builds I've seen have attached the engine drive sprocket to the fixie gear, but I'm considering a Manic Mechanic clamshell mount.

    line for drive train.jpg
    My mental estimation is the chain should have a very good path to the engine mount, and the idler pulley won't give me nearly as much trouble as my last build.

    The engine kit I will be installing is the flying horse 66cc from I've had good experience ordering several individual parts from them before, and they are an established business who have to maintain some level of responsibility for delivering orders (my last supplier screwed me over). I have a dual-cable brake lever that I'll install to free up the left handle for the clutch.

    I'm waiting on the engine delivery so probably not much more news until next week.

  2. darwin

    darwin Well-Known Member

    Cool bike, that seats gotta go though. On the rear wheel a sprocket comes on both sides? Is one bigger than the other for different gear ratios? Just flip the rim and that's it? What's the difference between a single speed gear and a fixie gear? Sounds like the same thing.
  3. BlueDestiny

    BlueDestiny New Member

    A fixie gear will turn the wheel both forward and backward, enabling you to brake by holding the pedals steady or pedal the bike in reverse. However, any time the bike is in motion the pedals will be moving with the wheel. A single speed gear is the standard bike gear that only rolls the wheel in one direction, letting it spin freely otherwise. The bike comes with both styles on the rear hub and you can switch them by flipping the wheel.
  4. butre

    butre Well-Known Member

    On account of the useless gear ratio, flip flop hubs don't necessarily work too well for motorizing other than with the traditional rag joint method (which I'll never recommend) unless you're the king of welders and can weld a larger sprocket to the fixie cog perfectly centered. That particular one won't work with a manic mechanic adapter without expensive custom machined radiused reducer bushings.

    My suggestion would be to relace that rim with a Shimano CB-E110 (or buy a rim that already has one) and use a manic mechanic adapter on that.

    That bike has an attractive design though, how much does it weigh?
  5. darwin

    darwin Well-Known Member

    Assuming the fixed sprocket is on the left side in above pic, not sure but say it is. It must be threaded on. Couldn't you put a cassette type sprocket on there instead of the fixie? Seems if you could that would be a great/reasonable solution to the other minor point on the bike is it doesn't have v brakes which I prefer.
  6. BlueDestiny

    BlueDestiny New Member

    Oh yeah I wouldn't put the drive chain on the fixie gear but several builds have mentioned they could mount the rag joint sprocket on the fixie gear somehow. I'll have to see how it will work when the engine arrives though, and I don't have a problem with the usual rubber-sandwich rag joint mount.

    The bike weighs about 28 pounds.
  7. Timbone

    Timbone Active Member

    I motorized aa 700c bike, one very similar to this. If you do a traditional, simple build (motor drive left side, no jackshaft), your clearance on the left chainstay will be TIGHT. You might want to do a mock up build to see where the chain will run and be prepared to stretch the stays to get an extra bit of clearance. If you let a 415 chain whip the frame it will eat it up.

    I think even rolling with 700c x 35's, you are asking for pinch flats. A sixty pound bike rolling at 25mph i hell on skinny tires. I am an advocate of 26" wheels with a minimum width of 1.95 inches.

    Good luck!
  8. BlueDestiny

    BlueDestiny New Member

    Thanks for the info! I'll definitely keep an eye on the tires and chain clearance. As for mounting the sprocket on the fixie gear, I found a thread where someone did exactly that on the same model bike, with pictures. It looks like the sprocket bolts fit into the teeth of the fixie gear, but the assembly is a bit sloppy. My biggest worry with this build is actually the exhaust pipe due to horror stories about the mounting bolts shearing off, but I can probably scrounge up some aluminum to bend into a bracket mount.
  9. professor

    professor Active Member

    My 2 cents is the bike is totally wrong for motorizing.

    The caliper brakes are poor (well, better than a single coaster brake) and one day you WILL need to stop NOW and will not be able to.
    I prefer to avoid pain and injury or worse.

    Hooking up a dual brake lever to an already wimpy brake deal renders the force you are able to apply (with one hand rather than 2) into 1/2 of the effort at the wheels.
    This is not considering the possible difference in pivot point and lever differences.

    Seriously, think about a bike with a minimum of 2 V brakes and bigger around tires.
    The feature of having gears is great too, as is a spring fork.
  10. darwin

    darwin Well-Known Member

    Do you have a link to those pics or can you post the pics, I'd like to see how it looks.
  11. Timbone

    Timbone Active Member

    If you are concerned about the exhaust hanging on those two little studs (and you should be!) just go to the auto parts store and get some of that metal muffler support strapping. Lowe's has a similar thing in the plumbing aisle (hanger strap) and support that exhaust every way possible!
  12. darwin

    darwin Well-Known Member

    Plumbers tape?
  13. SunkyWorks

    SunkyWorks Member

    From the other forum:

    "I used my dremel to make the sproket hole fit on the fixed cog and bolted the motor's sprocket directly onto the fixed cog. The bolt holes lined up perfectly with the cog teeth."

    Not my MAB.

    Attached Files:

  14. BlueDestiny

    BlueDestiny New Member

    Got the engine in yesterday and I've made good progress.

    Nearly complete.jpg
    All that's left is to finish attaching the clutch, throttle, wiring and fuel line.

    I opted to use a typical rubber sandwich rag joint. I tried mounting the sprocket on the fixie gear but it left nearly no room for the chain (as others have noted). Luckily for me, the sprocket sits very nicely over the fixed gear mount and the locking ring even fits over it, providing a bit of extra security.
    Sprocket detail.jpg

    Installation has been a breeze so far, especially compared to my first bike. The idler pulley is solid as a rock this time because the rear fork has oval-shaped tubes instead of circular ones, and the chain was easy to fit. I was planning on using a dual-pull lever for the brakes to free up the left handlebar, but for the sake of my sanity I'll save that for another day.
    Last edited: Jan 7, 2015
  15. BlueDestiny

    BlueDestiny New Member

    Finished the bike finally. All that's left to do is clean up the zipties, check the nuts and gas it up.

    3 4ths view finished.jpg
    Sideshot finished.jpg

    The last leg of the installation was delayed a bit because I had to sand down a crank arm to get it clear of the exhaust pipe. Luckily it was just a thick plastic coating so it wasn't much trouble. The killswitch wiring didn't have those little metal clamps so I stripped the wire a bit and just folded it into the CDI connectors. One odd thing with this frame/kit is how much excess cable I ended up with. I could have cut out nearly a third of the clutch/throttle wires since they were so long, but I'll save that for another time.
  16. alesterfeind

    alesterfeind New Member

    Looks good. I have been tempted to get one of those same bikes and put a motor on it. Seems like a fairly easy build.
  17. BlueDestiny

    BlueDestiny New Member

    Got the bike running today after a bunch of fuel-related mishaps. There are a few small issues left though, so help would be appreciated.

    -The killswitch is currently disconnected because I wired it wrong the first time. The engine has a blue wire, a black wire and white wire. The blue and black are hooked into the blue and black connectors from the CDI, the white is loose. The killswitch has one black wire and one yellow wire with no clips (just bare copper ends). I tried black-black and blue-yellow but the engine didn't start.

    -Engine will only run/idle with the choke open. This could be related to break in, but is it normal for the engine to die when the choke is engaged? It idles just fine without it, but I've only done cold starts so far.

    E: Did some searching about the choke, I guess I had it set correctly. It seems it should only be set closed to force a richer fuel mix when the engine is SERIOUSLY cold, not just room temperature.
    Last edited: Jan 8, 2015
  18. butre

    butre Well-Known Member

    the killswitch was wired right, something is wrong with the switch itself if it won't start in that configuration.
  19. KCvale

    KCvale Motorized Bicycle Vendor

    Very pretty build, nice work.

    Nice job on the sprocket and a good thing you didn't try to use the fixie alone.
    That sprocket screws on clockwise.
    Used on the pedal side it tightens as you pedal.
    On the left hand side however all the force is trying to un-screw it, unless that one had splines and just a hold nut of course.
    Using the rag joint and the hub as center is sweet.

    A pull cable cutting tool is a very handy tool to have for cable matching to clean up the look.
    The only cable you can't re-size (easily) is the throttle as it has a fitting on each end.

    That being said what I do is the route the throttle first taking out as much slack before the handlebars as possible so the throttle cable is 'just right' in the front, then match all the other cables to it.

    The tool was like $30 bucks around the corner from me but worth it, it gets used on every single build to the point it's about time to buy another but hundreds of cuts will do that to a tool.

    It is pretty simple to cable match.
    Put the cable on the lever and with the cable still in the sheath size the sheath to flow from the lever to it's connection and mark it.
    Then, pull the sheath away from the lever with the inner cable still attached leaving the amount of cable you need for the brake/clutch cable and cut both at your mark.

    What you have left is the right length sheath.
    Now just pull the sheath down a bit more and inspect your cut.

    Chances are there will be a bent sheath part that will obstruct the inner cables movement.
    Just nip it off with side cutters, and if need be use a poster board stick pin to open the cable end back up for smooth cable movement.

    Now just push the sheath back up to the lever where it goes, replace the silver cable end cap piece and hook it up.
    Don't ignore this part, without that cap your sheath will crumple there.

    If you look at the handlebars on most any of my builds you can see this in practice and to me worth the extra minutes to do every time.
  20. BlueDestiny

    BlueDestiny New Member

    That's some good info, thanks! Sizing the cables and installing a dual-brake lever will be my next step for sure.

    I think part of the reason the killswitch didn't work properly was not using metal caps on the wire end, making the connection bad. I'll see about scrounging some up but for now I kill the engine with the choke. The only problems left now are a (very small) fuel leak from the tank>valve connection and some sideways chain whip (caused by a crooked sprocket).

    Took it for a test ride and man this thing is fast even at tiny amounts of throttle. It's a blast to ride though and I'm already getting random people asking about it.

    Is it ok to take a fairly fresh engine up hills though? Once it's fully broken in it should have no trouble, but pushing this thing is rough with all the extra weight.