China Motors....

Discussion in 'Motorized Bicycle General Discussion' started by MadMaxed, Feb 15, 2015.

  1. MadMaxed

    MadMaxed New Member

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    okay i cheaped out and bought a china motor. .spr. . What would you guys suggest i remove and replace with higher quality parts.... I already have bearing in mind as well as sparkplug, boot and wire. the carb has got to go. hate asphyxiating my motor. but after that im unsure of.... Thanks in advanced
     
  2. frank66

    frank66 New Member

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    changing out those things takes only minutes to accomplish. try mounting it and driving 1000 miles. then you will see the beauty of a good and complete motorized bike.
     
  3. mapbike

    mapbike Active Member

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    Actually the NT carbs are one of the better parts that come in the kits, very durable, reliable, easy to tune and just plain work great on the China Girl 2 smokers.

    Upgrade mounting hardware is good, Sick bike parts has a good kit, replace the spark plug and boot with a good NGK setup is a good idea, if your engine came with the acorn nuts to hold head and cylinder, I suggest getting some high grade standard nuts and chunk those acorn nuts, I have seen some that were OK but most will cause you grief, I also use a dab of blue loctite on all the fasteners including the head/cylinder studs.

    Yes its a good idea to put a high quality upper wrist pin bearing in place of what could be a junk china bearing, some of them are better than others and hold up just fine but others dont and you have a trashed top end when they give way.

    Get you some small solder and a small propane torch if you dont have one and get an inexpensive set of wire gauge drill bits, that is all that is required to get the carb tuned correctly, buying jets is a waiste of money on these engines since you don't know what you will get no matter what the number on the jet is and you may end up with a whole hand full of useless jets since you will only need one.

    Here is a link to the best deal I've found on the wire gauge bits and pin vise to use with them.
    http://www.widgetsupply.com/product/WB05.html
    http://www.widgetsupply.com/product/SHG3-840.html

    Good place to get a high quality upper caged bearing.
    http://bearingsdirect.com/caged-cup...oller-bearing-id-10-x-od-14-x-l-15mm-iko.html

    Welcome to this great forum and I wish you the best on your build

    Map
     
  4. MadMaxed

    MadMaxed New Member

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    interesting. Does a ram air have any effect on thesee motors.?
     
  5. MadMaxed

    MadMaxed New Member

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    ngk.JPG also this is the spark kit i bought. spark plug is a NGK B8HS
     
  6. mapbike

    mapbike Active Member

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    never done anything like that, I wouldn't recommend it either since these 2 smokers need the carb jetted for the particular oil/fuel mix you intend to run and that is also dertermined by the amount of air that the engine is capable of flowing through it, anything that corces extra air in the engine is gonna lean it more that faster you go and, I see zero benefit to do any of that stuff with one of these engines, none of the fastest bikes out running these engines have anything like that set up on them and Im talking about people who have these engines pushing a grown man on a bike at 60+mph in some cases.

    Short answer is no, I dont think it would be effective and could cause a lean run condition that will kill one of these little engines in a short time.

    there are many performan e mods that can be done to one of these engines, some of those things have been discussed on here many times, many of the techniques arent shared by the people who have the fastest builds, but a lot of good info can be found on the forum, but at the same time we have our share of snake oil on here also.... so be aware that some of the products pushed by some members are just bling bling so to speak and truly offer no performance gains.

    best wishes on the build and as you'll see on here many times, starting off with and engi e that has fairly good balance factor is important to overall good performance, fortunately for all the new comers to this hobby it seems we are getting much better balanced engines nowadays than many we were getting in the past, so this will help a lot of people end up with a better performing engine.
     
  7. mapbike

    mapbike Active Member

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    Thats an excellent upgrade.
     
  8. frank66

    frank66 New Member

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    what bike and what do you want to do w it?
    unique or mainstream? everyday or showbike? how often do u want to fuss w it?
     
  9. MadMaxed

    MadMaxed New Member

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    i got a hampton cruiser. just an everyday road bike i work like a mile down the road. but im also planning on hitting a few trails with it. Im interested in jug rotation soon.Iknow ill have to mess with the ports. Havent got the engine on will be delivered in the mail tomorrow. But i do plan on moding it for longevity not for speed.


    hampton.jpg
     
  10. 2door

    2door Moderator
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    What do you plan to achieve by rotating the cylinder? If you're having frame to carburetor clearance issues there are other ways around that. Otherwise there really is no benefit except routing a custom exhaust system. Don't expect any 'ram air' power increases. Motorized bycycles don't go fast enough to get any real boost from incoming air. What little there is might require a slightly richer fuel/air mix but then you hurt your low end performance. Unless maybe you plan to ride WOT all the time.

    Just curious about your reasoning.

    Tom
     
  11. mapbike

    mapbike Active Member

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    (Quote: "But i do plan on moding it for longevity not for speed.")

    If this is your intent for the build,

    1.just do a simple deburring of the ports, (don't raise or lower either exhaust or intake port)

    2. get a piece of wet dry 320 grit sandpaper and tape it down flat on a piece of plate glass, and true up the surface of the cylinder deck and also the head sealing surface if you plan to use the kit supplied head.

    3. as I said before I recommend getting some regular or flange type 8mm nuts to fasten head down instead of the acorn nuts that usually come on engine.

    4. install a better upper bearing when you go back together with it and be sure to oil bearing and piston pin good when yuo install them.

    5. use loctite BLUE on all nuts and fasteners and get them good and snug but don't get to rough with them since most are small 6mm studs and bolts and they are fairly soft steel.

    6. The rear mount of the engine to frame is the most critical, make sure it sits flat on the frame, do NOT use rubber or anything else between engine and frame, tighten stud nuts good with loctite on threads but dont over tighten or they will fail in a short time, I actually like to double nut the rear studs by adding and extra nut on each side and then tightening the outter nut down very tight against the inner nut while holding the inner nut secure with another 10mm wrench, just extra security since the rear studs will normally be the first to give a problem if theye aren't done correctly.

    7. Be sure to get sprocket straight and true on wheel.

    8. Lastly, make sure to get he carb tuned properly for the mix you plan to run, run whatever oil and mix you feel confident with, I will not say more than this since this oil and ratio topic always opens a big can of worms on here...LOL!

    best wishes on the build.
     
  12. Davezilla

    Davezilla New Member

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    For longevity and not speed... I agree with everything Map said above... the only thing I do different is the rear mount. I buy a second mount block and use longer studs so the seat post tube has a Very solid fit and these aluminum mount blocks can be sanded, filed, or milled down for a better fit in a tight frame.
    the front mount should match the frame as closely as possible as well. I cut slots in my lower frame tube and pushed a 1" x 1/8" thick piece of steel flat stock thru the frame and welded it into place for the front of the engine to bolt directly to, but any nice solid mounting setup will work, just don't use any rubber anywhere on the engine mounts, this will spell out disaster and a LOT of vibration transfered into the grips and seat.

    The NT carb will do just fine on a "longevity, but not so fast" bike, but they do perform really nicely for what they are... mine and quite a few other's bikes are doing well over 40mph on this carb, and mine is doing it running the stock 44 tooth rear sprocket.

    Porting is optional, but cleaning up the excess nikasil plating that overhangs into the ports will ensure longer cylinder life, any overhanging plating will start the plating to peel off the inside of the jug, just a quick cleanup and chamfer in there will ensure long life for your cylinder and rings.

    Rear sprocket, you want to adjust it until there.s no wobble at all if possible, but anything under 1/16" side to side wobble will keep the chain on, this may need adjusting a few times before it stays put and it's easier to adjust the second time around as things start to settle.

    A good investment for the rear sprocket is the Manic hub and sprocket setup that eliminates the rag joint, but the rag joint setup is also reliable once properly adjusted and set in.

    I definitely agree on the better quality wrist pin bearing, the stock ones are usually too narrow and leave about 2mm or so of side to side play, there are better bearings available that'll fill in this void as well as live a lot longer than the stocker.

    I'll also add getting a better head like the Puch Hi Hi head or Fred head for better cooling, the stock heads are ok for just putting around on but they're also very prone to overheating since there's not a lot of cooling surface and they're also cast kinda on the thin side.
     
  13. MadMaxed

    MadMaxed New Member

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    yeah its going to be my main transportation just looking at some ideas. But considering just leaving most stock now. but change bearing and various other parts for longevity since this is my first project ill leave the performance mods for my second build
     
  14. MadMaxed

    MadMaxed New Member

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    ^ Thanks all. Upgrading the head seams to be a great idea. I also plan on reinforcing the spokes on the back for extra security. And for sure the wrist pin,and the other four main bearing i have heard about. Other than that my kit comes in tommorw for sure ill post pics when finished. =)
     
  15. Davezilla

    Davezilla New Member

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    Sounds good... Keep us posted on your build and don't hesitate to ask if you need anything...
     
  16. mapbike

    mapbike Active Member

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    I agree with Dave on upgrading the head also, I dont un the stock heads anymore since my bike are run in this really hot dry Texas climate and I ride mine fairly harz and fastfor many miles at a time usually, I dont ride mine to my work alot but when I do its a 32 mile round trip and I run wide open a good part of that since about 22 miles of it is wide open road.

    The Puch heads do a great job, dax sells them already drilled for the 8mm studs or you can get the Puch hi hi 70cc head from treatland.tv also but youll have to drill the hole out yourself since they're set up for 6mm studs.

    The 6cc chamber Fred head is an excellent head, looks great and does a good job of keeping the engine cooler running.

    Like Dave has said for just putting around its not as big of an issue in my opinion either but for long hard runs the heads with more surface area to wick heat away from the engine add life to the engine by helping it to run cooler.
     

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