What typically fails on a ChinaGirl motorized bike

Discussion in 'Motorized Bicycle General Discussion' started by Deimus, Dec 14, 2012.

  1. Deimus

    Deimus New Member

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    For the experienced out there, what are the typical failures that you've had to repair on your ChinaGirl bike? What breaks and what is bulletproof?

    For example, from reading here I quickly learned that the factory front fender L-bracket does not stand up to vibration resulting in a potentially catastrophic failure. Based on this, I replaced the thin factory front fender mount with a custom made one from 1/8" flat stock.
     
  2. killercanuck

    killercanuck New Member

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    Yea, on the bike itself the fender mounts are tops on the list. Next would be the engine chain idler slipping into rear spokes, I used to drill a hole right through into the chainstay to get it to stay put, but lately am drilling/tapping a short lock-bolt so as not to weaken the stay with a hole.

    Failing spokes can be a pain but not usually catastrophic, and most are caused by flying over potholes doing 25+mph... what can be disastrous is a frame cracking from the same thing. So dodge those potholes, lol.

    On the engine itself, I'll try to keep the list short.
    -First on that list would have to be the engine mounting studs breaking, replace with real steel studs asap. They're M6x1 btw.
    -The exhaust studs can break if you don't use the muffler clamp, same size.
    -aluminum intakes are known to randomly snap off(or in half) from vibes
    -magneto's can fail from moisture, seal up where the wires go into the case
    -cdi's fail randomly if wired incorrectly, ie. white wire kill switch, or bare wires shorting out

    less common are head gaskets and internal bearings. Piston needle bearings/bushings, crank bearings.

    I've covered a few bases, but like with anything, there's always something that can go wrong. Best to keep your eyes open and do a good visual inspection once in a while.

    gl.
     
  3. Deimus

    Deimus New Member

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    That's a great post. Thank you.

    Currently, I am using the included rear motor mount studs on my first build. I will put these on a list of things to replace. Same for the exhaust studs. My front motor mount is not from the kit. Also, I'm using M6 cap screws to mount the intake. I did notice that the kit studs fit looser in the block than an actual M6 bolt.

    I will check to insure the magneto area is sealed. Thanks.

    I just finished installing the chain and tensioner. I discovered I was having an alignment issue with the tensioner. The issue was that the tensioner wheel was not aligned to the chain. Instead it was aligned to the lower chain stay because the tensioner bracket, of course, is bolted to that stay. So I put the bracket in my vise and used a big pipe wrench to twist the tensioner bracket a little to align it with the chain. That bracket is pretty thick so it takes a lot of effort to twist it the small amount needed. Now my tensioner wheel supports the chain in alignment allowing it to feed onto the sprocket cleanly.
     
  4. maniac57

    maniac57 Old, Fat, and still faster than you

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    I tack weld the tensioner for security. Muffler shops can do it. I also replace the cheap kit chain before I start a new kit. The chain that comes with the kit is junk. I use #40 roller chain, but there are several options to upgrade.
    Check all nut&bolts REGULARLY for tightness and use threadlock where needed. (BLUE not red)
     
    #4 maniac57, Dec 15, 2012
    Last edited: Dec 15, 2012
  5. Deimus

    Deimus New Member

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    Looking at the chain size chart posted in another thread, #40 chain has a roller diameter of .312 and an inner gap size of 5/16. The chain in the kit has a roller diameter of .306 so does the #40 chain fit down on the sprockets fine? And since the kit rear sprocket is only 1/8 thick, does the 5/16 inner gap not cause any support issues for the chain?

    Keep in mind that only the "numbers" would seem to suggest an issue that's why I'm asking. I'm not saying that there are issues because I don't have any experience with this.
     
  6. GearNut

    GearNut Active Member

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  7. Predator303

    Predator303 New Member

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    "What typically fails on a ChinaGirl motorized bike"

    Everything that comes with it. Let me think a moment what actually didn't broke.......

    Yeah, the only thing I didnt had to replace but did replace for gear ratio, was the rear sprocket. Everything else is junk and broke - including the tank.
     
  8. bigbutterbean

    bigbutterbean New Member

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    That result is not typical for those who know how to properly install a China kit in their bike. I know, you'll probably get mad at me again and say you dont care what I think, but its true. It takes a great amount of care to install a china kit. I did not know this when I bought my first kit, and I had some troubles with it. The difference is, I knew and accepted it as user error instead of blaming the kit/manufacturer/vendor.
     
  9. tooljunkie

    tooljunkie Member

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    the decal hasnt fallen of the motor,so im doing good.
    seroiusly,what all the above said.use silicone sealant to waterproof the wiring where it goes into engine,seal it from inside as well,including the cover gasket.getting caught in the rain will surely result in cdi/mag failure.
     
  10. Predator303

    Predator303 New Member

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    Why should I get mad? If you want to use it on the sidewalk for 5 minutes its probably ok, but I used it as motorcycle with higher top speeds and long distance and that thing was extremely unreliable. Anyways, I got something great now. Everybody asking me to build one of those bikes, I tell them to forget about the China Kits and invest in a small 4 Stroke instead. Cost more, but in the end its cheaper and less headache and driving instead of repairing and waiting for parts.

    My opinion: Dont buy a china Kit at all. I would never do it again.
     
  11. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    My cure for this is ditch the fenders and don't ride in the rain.
     
  12. bigbutterbean

    bigbutterbean New Member

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    I actually agree with you about the reliability and waiting for parts all the time. I'm going 4 stroke as well, with a 98cc flathead Lifan (honda clone similar to the predator line). I also agree about the cost factor. Spend a little more upfront, but spend a lot less later, and you get to drive your bike way more often to boot. We got off on the wrong foot before, but I apologize. I can rub people the wrong way sometimes.
     
  13. Deimus

    Deimus New Member

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    After installing my first kit, I can easily understand how important the installation fitting details would be to the stresses on the little ChinaGirl engine. Starting with the installation of the wheel sprocket. That thing was impossible to true at first for me. Then I worked out a method using my dial indicator that made the installation painless and precise. I posted a thread on how to do this to hopefully help others. (Sprocket installation how-to).

    Also, details I learned here and followed included removing the engine covers and checking the installation of the magneto, clutch gear and slant gear, and the seals. I found my clutch drive slant gear barely installed by the factory. I had to remove it, file the burs they created on the shaft, then reinstall the slant gear. My seals seemed fine but it was good that I checked them. In addition I didn't use many of the bolts and studs included in the kit because they either fit loosel or the metal was just too soft.

    Keep the experiences coming. :)
     
    #13 Deimus, Dec 16, 2012
    Last edited: Dec 17, 2012
  14. Predator303

    Predator303 New Member

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    Thats the first thing I would recommend if you want to live long. Go to a hardware store and replace all screws and nuts with higher grade (nut butter grade like they come with the kit).
     
  15. The_Aleman

    The_Aleman New Member

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    My experiences and opinions to get mileage out of one:

    First-off, gotta get rear sprocket straight as can be and bolt down the engine so the chain lines up. Next tweak the idler bracket til the chain runs straight on the pulley.
    Keep chain under ~3/8-5/8" deflection. I actually got almost 2K miles on the stock kit chain in almost 2 years with this method, the engine had to be cocked in the frame
    a lil bit to get a straight chain. I also munched the heck out of my 34T sprocket because I put so many miles on that chain lol

    2nd, get a proper killswitch working and make sure you have no intake leaks. The choke should be able to kill a warm motor quickly.
    Definitely use allen cap screws with lockwashers on intake and exhaust headers. Blue Loctite or equivalent optional.

    3rd run a proper mix and don't overrev the dern thing lol.
    Running them more or less out of the box and not revving it much over 6K will net you a torquey engine, from my experience.
    Gear it under a 40T and pedal hard til it has a few hundred miles on it :D
    Stock kits with 44T keep it 26MPH or less during break-in, IMHO. If it shakes a lot at 26, check mounts. If mounts are OK you got a shaker. That's a Monday/Friday engine.

    If at all the top end starts knocking, you've over-stressed the upper conrod bearing. Rebuild the top end/warranty and start over lol

    When it's properly broke in, it will be very susceptible to mods and should last a decent while, depending on the day of the week your engine was built rotfl
     
  16. littletinman

    littletinman New Member

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    The actual engine parts that have ever broken on mine are a piston malfunction (part of it disintegrated) and all four large bearings went out.

    CDI and magneto is more electronic and are very easy to replace.
     
  17. maniac57

    maniac57 Old, Fat, and still faster than you

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    I must have gotten a good one every time. My experiences with china kits has all been positive! I have had six or seven of these engines myself over the last few years,as well as selling at least that many more and I have had universally good results from them. I fix what needs fixing and take good care of my stuff. I also ride the wheels off the buggers! Opinions vary about quality, but there is NOTHING close to the value for the dollar in the motorised bicycle world.
     
  18. Deimus

    Deimus New Member

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    I hope my first kit and build turns out reliable. I've followed most of the recommendations that I've read here on the forum so far and I was careful with the installation. I've only had it finished a few days now and the weather has only permitted short rides. Even after only about 15 miles total so far, the little engine is already running smoother and idling better.

    I've been reading posts here about both the ChinaGirl 2-stroke builds and the various 4-stroke builds. For my personal taste, I think the 2-stroke bikes are mechanically beautiful machines due to the clean look of the slim components. The 4-stroke builds just doesn't have that same simple clean look. Now some of the extreme expansion chamber exhaust systems take away from the looks for me even though functionally they may be better.
     
  19. bigbutterbean

    bigbutterbean New Member

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    Just remember you can choose function and you can choose form, but you cant always choose both. I will take function over form any day of the week.
     
  20. Deimus

    Deimus New Member

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    This is mainly a hobby for me so form is very important; though, I expect I will be able to get very good functionality as well. At this time, my expectations for the little engine's performance will be based on running smoothly and sipping fuel.
     

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