are 2 stroke engine kits the same?

Discussion in '2 Stroke Bicycle Engines & Kits' started by paul, Nov 13, 2008.

  1. paul

    paul Active Member

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    absolutely not! i have been researching this to try to find the answer. their is numerous company's producing the motors in china. they may look the same but they are not. what made me look into this is my first motor was the cheapest i could find and it had bushing bearings and wanted to replace them with roller bearings but they would not fit. the similarities in the motors is basics like carburetors and exhaust mounts are the same. however their is like 4 different styles and lengths of exhaust available of different kits i have found. same with cdi's. they may look the same but they are different depending on who manufactures them. some have less winding and less windings mean less power. the ohms on the cdi's can range from 257 ohms to 353 ohms of course the 353 ohm cdi is the better of them. same with carburetors. their is 2 different size slides and one will not work on the other. the bigger one is 1.5 mm larger. spark plug wires i know this from my kit. it was a piece of junk and it was like having a new motor when i replaced it. the engine itself some use 6mm cylinder studs, others use 8mm, Counter shaft sprockets are different. Some have larger cooling fins, and more. Here is what items I have found that are similar and can work with most of the other engines. Side covers, Magnetos, CDI's, Spark Plugs, Carbs. kinda like some car parts are interchangeable or AA batteries all look the same but they sure the heck are not. however things like pistons, rings, bushings ect are not interchangebable. so to wrap this up they may look the same from the outside but inside these engines are different and each manufacture in china has thier own inhouse inspections. take your time when you buy an engine and make sure it has a good cdi, wires, bearings ect. hope this helps clear things up a little
     
  2. thatsdax

    thatsdax Member

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    you got it. What you are saying is true. I do not know how to convey it any better that what you have done. . I am not the best at those things. But I can tell you this Paul. You understand what the deal is with these engines and how they differ. And they are not the same. Only if they come from the same factory will they be the same. Thanks again.. Sincerely.. Duane...
     
    #2 thatsdax, Nov 13, 2008
    Last edited: Nov 13, 2008
  3. xlite

    xlite New Member

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    I agree too. Most who say they are all the same are talking through their hat. You really find out when trying to get replacement part after a couple years.

    In fact it's difficult to get similar motors from the same vendor!
     
  4. Motor Boys

    Motor Boys New Member

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    All very good points Paul, and all very true, a buyer should do there homework.
     
  5. yojimbo

    yojimbo New Member

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    where can i find quality kits UNDER 49cc's? i live in il and they just passed a law limiting the size and hp right when i was about to open shop!
     
  6. Nougat

    Nougat New Member

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    yojimbo, many of the kits I've seen advertised rate the "small" engine at 48cc. My RAW kit is marked 48cc.

    Also, the only IL state law I'm aware of actually legalizes "low-speed gas bicycles" to 1HP, but says nothing about displacement:

    Illinois General Assembly - Full Text of SB0236
     
  7. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    My research tells me much the same as what is stated above. You have to learn a little about the engine before you buy, read what others say. I feel safe with ThatsDax for that reason. (...And I am not affiliated, nor have I been paid or pressured to endorse.)
     
  8. analogtom

    analogtom New Member

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    What is the highest quality engine being sold? With the highest quality parts etc...

    What would you buy now to build a bike with?

    Or is there a Best Company that can be trusted ?

    I like the simplicity of the motors but am looking for a quality motor for my next build, I am looking at 4 cycle engines due to quality of the brands (ie honda.... )
     
  9. stuartracing

    stuartracing New Member

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    Ok I have 2 motors....One is the bushing type rod bearing motor(small end)....And the other is cage type bearing....Piston pin location is way different too....I bought a spare piston,but ony good for the cage bearing motor because of the pin location on the piston....
    So would the billet head work on either of these 2 motors or would you need to use another head gasket on it????
    Paul.....
     
  10. wildemere

    wildemere New Member

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    Bushing motors use a 11mm wrist pin, Bearing motors are 10mm.

    The rod length is also different.

    Parts are not easily interchangable between the 2 setups.

    Bushing motors seem to run faster though.
     
  11. jamrhein

    jamrhein New Member

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    So far this is my 3rd bicycle motor kit. The first one was stolen with a set of bolt cutters, as it was locked up outside, and I never got to finish breaking in that motor, of which I paid $170.00 for including S & H. Although, even so in the short time I had it, I travelled probably 100 miles, and either the CDI or magneto failed, probably due to overheating of the motor. I bought this motor local, from Pirate Cycles, right here in Massachusetts. After replacing the blown electrical part, the motorbike was stolen.

    The second motor, I bought from California from "Boy Go Fast" and I ran it over 20 mph during the break-in period, against the manufacturers recommendations for a short time, and noticed the motor wasn't breaking in properly, as the performance was starting to decrease noticably, so I filled the gastank with 16:1 2-stroke pre-mix, locked it by chaining it to a tree in my backyard, and figured I'd let in run of of a full tank of gas twice, so I could guarantee I didn't drive it over the recommended 20 mph to finish off the break-in period. The motor ran thru about half the tank of gas before it stopped running for some reason. I restarted the motor, and tried to get it to run thru the other half a tank of gas. It died again before running out of gas, and I wasn't able to get it to run since. It looked identical to the motor I bought from Pirate Cycles, made in China, as well, so I figured it must be a common problem and suspected the same ignition electrical problem. Since there was no repair manual available for purchase, with the ohms specifications, and/or other testing procedures for the CDI box and the Magneto coil, I purchased both and installed them, along with a new spark plug although the motor still wouldn't start, even with a spark present.
    I tried squirting ether starting fluid in the carburetor. I also took out the spark plug, and squirted a small amount of 2-stroke oil into the spark plug hole, to seal the rings, in case it had too low of a compression to try to get it to start in this manner, which always works, but didn't in this case either. It should have started in one of these manners, althogh it didn't. The compression tested around 60 psi, which seemed low, but should have started anyway. The motor wasn't completely broken-in yet, although that could have been normal at that stage; again with no availability of a repair manual, I had no way of checking it against manufacturers specifications.
    So I gave up on this motor, and ordered a new motor only, not the whole kit.
    I ran this motor meticulouly under 20 mph for a 20-mile round trip after I first installed it. It seemed to be running kind of hot after the first 10 miles, so I turned around, and drove it home trying not to drive it anymore than possible 'til I figured out the problem.
    I had a 16:1 mix of gas in the tank, although when I looked at the clear fuel line, there was no hint of color due to the color of the 2-stroke oil mix passing thru it, and I figured somebody around here may have dumped some straight gas unmixed into the tank leftover from mowing the lawn, thinking they were doing me a favor, not realizing it requires a 2-stroke mix; but the gas in the tank did have a hue of green color in it, obviousy being in such a larger concentration compared to the thin fuel line.
    Also, I was using some cheap 2-stroke oil, Itasca, of which I never heard of, that I bought from a supermarket instead of an auto parts or hardware store; and it's possible the cheap oil could have contributed to the problem, but I'm not sure.
    I added some more 2-stroke oil and gas to the tank to bring the gas mix down to around 12:1, which helped, a bit, but the motor developed a very noticable piston rap, over the next few days, meaning the piston to cylinder clearance was so excessive, the piston was actually slapping around in there instead of just sliding up & down, as it should; which causes the piston knock or rapping sound, and also causes premature destruction of the motor if not fixed.
    So I decided to tear open the previous motor I still had laying around, the one I gave up one, and measured the piston to cylinder clearance in 6 different locations; of which varied from .004 inches to .015 inches, which is clearly unacceptable. Normal clearance for similar motors is .001 to .002, although, again, no manufacturer's specs available for comparison.
    I emailed customer support and they were guessing the catalytic converter, which is an upgrade used in my kit from the non-upgrade standard muffler, may have been causing the motor to overheat.
    It seems mostly unlikey to me, since the cat. converter is a straight-thru design; in that there is no restriction of the flow of exhaust gases as it passes thru it. And since it's long, I would imagine it would act as a heat sink, drawing heat away from the motor instead of back to it. Although, it was odd that I noticed the cat. converter didn't smoke one bit on this new motor, as it did on the previous motor, which is weird and somewhat seems like it seemingly could be running so hot that it's burning up all residual unburned 2-stroke oil-in the form of smoke, in the similar manner that it does to unburned gas, as it was made to do.

    These motors don't seem too reliable, although maybe they are if they are broken-in properly, of which I haven't be able to get to that point with these first three.

    Has anybody noticed such similar problems? Are there much more reliable motors available that break-in easy and don't have this problem and have some type of longevity to them? All three of these were the 66/80cc made in China motors.
    I'd like to stick to the highest displacement unless the smaller, say 48 or 49cc motors have the same power. And is there a better way to break-in these motors, which will run fine thereafter for a good longevity?
     
  12. GearNut

    GearNut Active Member

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    Break in the engine with 20:1 pre mix ratio. Use a quality pre mix oil made for motorcycles. Opti2, Amsoil, or Maxima brands come to mind.
    Do NOT use pre mix oil made for outboard engines they are water cooled and have different requirements than air cooled engines.
    Do not be afraid to go over 20 mph for SHORT bursts, like 100 yards or less, once in a great while.
    It will actually help break in the piston rings better and faster.

    Ride the engine for 15 minutes or so and then let it cool down completely, a 1/2 hour minimum.
    I would ride it for 5 minutes and let it cool down. Then 10 minutes and cool down. Then 15 minutes and cool down, ect.
    Long trips on an new engine will kill them if you do not let them cool down frequently.
     
  13. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    16:1? 12:1?!? That can cause a lean condition (fuel to air) and can cause other problems as well.

    24:1 is really too much oil, but I recommend running a tank at 24:1 then going to 32:1 or even 40:1 for the next couple hundred miles. Always check the plug when you make ANY changes and see what the engine is doing mixture-wise.
     
  14. stuartracing

    stuartracing New Member

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    What is the deal with these people who think that breaking in a motor without actually riding it is going to work....Met one dude who strung his bike up in a tree and let it run through a tank of gas to break it in.....It don`t work that way....Ya have to put a load on it.....Ride it brother....I`ve had 4 of these and to tell ya the truth,I never worry about breaking it in....I just take It a little easy at first to get it dialed in and then go out and have fun with it....My motors all worked great.....
     
  15. Goat Herder

    Goat Herder Gutter Rider

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    The rings don't seat in proper without a load.
     
  16. jamrhein

    jamrhein New Member

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    The recommended mixture of gas to 2-stroke oil by the manufacturer is 16:1 during the break-in period, to ensure the internal parts of the motor are lubricated properly. A higher ratio of fuel to gas such as 24:1 or 32:1 means the new engine is getting less oil to lubricate the new motor, and more of the chance of ruining the new motor due to lack of adequate lubrication.
    Not only does oil lubricate the motor, it also cools the motor, of which is an air-cooled motor, and needs all the cooling it can get during break-in, unlike water-cooled motors, as there is a lot more friction inside the cylinder, until the cylinder reaches a slippery, shiny surface, with less friction, and thus doesn't need the extra lubrication and cooling as a non-broken in, new motor, which hasn't achieved that slippery/shiny surface, which can run on less oil, for more horsepower.
    A lean gas to air condition is controlled by the carburetor, not the gas to oil mixture.
    Some carburetors have an air mixture adjustment screw for controlling the richness/leanness of fuel/air mixture, although mine doesn't.
    Other than that, the only other ways of controlling the air/fuel mixture are to change the size of the tapered needle jet, which controls the air/fuel mixture during mid-throttle use; and change the main jet size, which controls the air/fuel mixture during full throttle use.
    Also the choke can be applied partially during running application, to make the air/fuel mixture richer, which in turn will also allow more gas/fuel mixture to enter the motor in relation to the air entering it, and will help cool and lubricate a new motor for break-in purposes.
     
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  17. GearNut

    GearNut Active Member

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    Given the carburetor jetting remains constant, not altered, a 16:1 ratio will run leaner than a 32:1 ratio due to the fact that the oil mixed with the gas affects it's specific gravity. In other words 16:1 weighs more than 32:1.
    At any throttle position, 16:1 would allow less fuel through the same jet than 32:1.

    16:1 can be lean and 32:1 can be rich if the jetting is not set appropriately for the fuel/ oil ratio being burned.
     
  18. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    There is so much wrong with the above statement, I don't even know where to begin.....so I won't.

    Apparently, you read the instructions that come with some kits, in which case you should have known better than to believe part of them (16:1).
     
  19. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    GearNut is correct.
    So is Goat Herder.
    jamrhein....not so much.
     
  20. talltommy46

    talltommy46 New Member

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    I'm a new guy on these pages.. But, just had to add my 2c on this topic... Bikeguy Joe, and the others are absolutely right! No question! I have 30yrs of racing dirtbikes under my belt, MX, Offroad, and some RR too.. 90% on 2stroke engines.. I can jet a 2stroke by the feel sound and smell.. Have a stable of vintage racebikes, most run at 12-13.5 comp ratios and VP Racegas at 50:1 mix... Mmmmmm, love the smell of premix in the morning! Yes, go with the 24:1 mix for breakin and 30:1 for reg use... After ya get it fine tuned(jetted), then move up to 40:1, and rejet again... Remember every mod, will need a rejet..
     
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