Pretty little 49cc engine!

Discussion in 'Motorized Bicycle General Discussion' started by maniac57, Nov 13, 2014.

  1. maniac57

    maniac57 Old, Fat, and still faster than you

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    I was lucky enough to have this beautiful little 49cc motor come across my bench this week.
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    It's got one of the best quality cylinder castings I have ever seen on a Chinadoll with a huge round exhaust port and exceptionally clean fins.
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    It also has the long curved clutch arm I normally only see on recent motors, but the rest seems like a much older better quality engine.
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    It has the square head with the tiny 10mm head nuts and the older style, high quality machine grey paint (like the old bridgeport mills had)
    Overall it looks to be a much better built engine than you usually see.
    The huge exhaust port has me thinking it might be time for me to pick up a porting tool again after all these years since this one looks to be worth the effort even though it's only a 49cc. I recently gained access to a compressor so all I need is a die grinder and a few carbide burrs.
    It's been my experience that the older 49's will rev a lot higher than most any 66cc with the better crank balance inherent in the smaller displacement.
    With that huge exhaust port, it needs is a bigger intake and some transfer aiming and case-to-cylinder matching and it should really wake it up. Nice thick casting with PLENTY of room for any sane porting makes me think it will be fairly durable too!
    Can't wait until it warms up a bit here to slap it on something and see what I get for a baseline!
     
    #1 maniac57, Nov 13, 2014
    Last edited: Nov 13, 2014
  2. maniac57

    maniac57 Old, Fat, and still faster than you

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    More pics
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  3. Dan

    Dan Staff
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    Cool, Manic


    What ya gonna put her on?
     
  4. maniac57

    maniac57 Old, Fat, and still faster than you

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    Don't know yet Dan. That's half the fun!
     
  5. HotRodRob

    HotRodRob New Member

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    Wow, those castings are very nice. Even around the outside of the ports is all smooth which I have never seen. That exhaust port is awesome. Is the exhaust port round on the inside of the cylinder? A closer pic would be cool. Also, I'm interested in what the intake port looks like. Have you had a look inside the cylinder? I bet with a lil elbow grease you can have her lookin good as new. Nice find Maniac.
     
  6. 2door

    2door Moderator
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    Have you actually measured the bore and stroke to confirm the CCs? Obviously someone has installed an aftermarket slant head. I don't know of any (I might be wrong here) that had 6mm stud holes so the head must flop around somewhat on the small studs. Will that present a problem seating the head on the gasket sealing surface or are you going to use a 49 head?

    Tom
     
  7. MotorBicycleRacing

    MotorBicycleRacing Active Member

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    That is the original head off a Naitong JaiLi 48cc motor and they have 6 mm holes. The 48 cc cylinders had 6 mm holes too.

    Mine had the JL logo cast on the underside of the head and on some of the covers.

    They also made a 48cc with the same round exhaust port and an iron liner.
    The carb bolted right on the back of the cylinder so did not use an intake.
     
  8. fatdaddy

    fatdaddy New Member

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    DAAAAAANG, that exhaust port is enormous The 66 aint even close. are ya sure it's a stock cylinder?
    fatdaddy
     
  9. maniac57

    maniac57 Old, Fat, and still faster than you

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    The head has weird little cast-in pedestals rather than washers under the head nuts. Clearly NOT a normal slant head. Has much smaller chamber that fits this smaller bore perfectly. Really nice engine!
    Thanks for the input on origins Neil, I'll check for marks when I dejug it.
     
  10. 2door

    2door Moderator
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    Thanks for the input, Neil. These little guys must be somewhat rare?

    Tom
     
  11. Davezilla

    Davezilla New Member

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    That does look nice and with that exhaust port sized and shaped the way it should be... Maybe this is an early engine before they figured out which corners they could cut and it still runs, but it sure is a nice one.
     
  12. maniac57

    maniac57 Old, Fat, and still faster than you

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    Pulled the engine down today and found more excellent quality! It has the huge intake flange, same size as a 66cc exhaust but with an even bigger port! This thing is gonna SCREAM!
    The rod feels nice and tight on both ends and the pin is unmarked, as is the piston and cylinder. Top end is totally useable and in great shape.
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    Now for the BAD news...
    The mains are wasted. Binding and crunchy bearings mean I have to split the cases.
    I'm hoping it has the same size mains as the 66cc so I won't have to wait for a set of bearings...
    Anyone out there know if the 49 has the same mains as the 66?
     
  13. Dan

    Dan Staff
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    Really nice to read "excellent quality!" for a change.
     
  14. Greg58

    Greg58 Well-Known Member

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    Mains are the same size, I built one of my engines the first of the year. Maniac did you notice how close the cases are to the crank? No need to stuff or anywhere to put anything for that matter. The crank in both of my 48cc engines fit the same way, neither cylinder has those size port tho.
     
    #14 Greg58, Nov 19, 2014
    Last edited: Nov 19, 2014
  15. maniac57

    maniac57 Old, Fat, and still faster than you

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    Thanks for the confirm Greg! Every part I've seen looks great so I expect nothing different inside the case...
    This one is going under the grinder before I place it back in service! Those huge ports are just BEGGING for a performance build....
     
  16. maniac57

    maniac57 Old, Fat, and still faster than you

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    That gigantic intake cave needs a nice custom manifold and a big dirtbike carb to take advantage of all that flow potential I'm thinking....
    With a port like this, there's no reason to stick with the tiny stock induction!
     
  17. KarenH

    KarenH New Member

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    Obviously I've got a lot to learn still. Any one have a basic/generic diagram identifying all the parts? That's what I need so I can better communicate my issues and better understand the help I get! lol
     
  18. Dan

    Dan Staff
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  19. maniac57

    maniac57 Old, Fat, and still faster than you

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    Well I got some bad news...
    The mains are NOT the same size as the 66cc. They are bigger! (And seriously wasted!)
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    The third picture shows a standard 66cc main bearing in the 49cc case. Quite different unfortunately.
    Now I'm dead in the water since I cannot afford to buy bearings at this time.
    :(
     
  20. MotorBicycleRacing

    MotorBicycleRacing Active Member

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    One of the selling points of those 48cc motors was bigger bearings.
     
    #20 MotorBicycleRacing, Nov 20, 2014
    Last edited: Nov 20, 2014

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