No power gain after installing header and bigger camshaft in HS

Discussion in 'Motorized Bicycle Trouble Shooting' started by socialdistortionkid, Jan 24, 2013.

  1. socialdistortionkid

    socialdistortionkid New Member

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    Added a header from AGK to my huasheng 142f 49cc engine and the power improvement was barely noticeable and i read on this forum that im not going to see a difference unless i added a bigger camshaft so i installed the .175 lift cam from AGK in my engine and set the valve lash at .007 with a feeler gauge. There is no noticeable gains from the Camshaft and Exhaust combo. What do i need to do to get my engine set up for the upgrades i installed?? I appreciate the help.

    -Chad
     
  2. maniac57

    maniac57 Old, Fat, and still faster than you

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    I'd try a tubular manifold and slightly bigger carb. You seem to have the exhaust side handled, move to the induction.
    I have no personal experience with this motor, but hot-rodding basics still apply.
    It's an air pump. Move more air= burn more fuel= get more power.
     
  3. Greybeard

    Greybeard New Member

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    Did you reject the carb? Both mods require a richer mixture than the stock carb has.
     
  4. BigBlue

    BigBlue New Member

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    Here's a statement from the camshaft product description:
    "Only use this camshaft for high performance applications using our big bore carb and free flowing exhaust."

    You might want to take a look at your plug color before you toast your engine.

    Good Luck,

    Chris
    AKA: BigBlue
     
  5. socialdistortionkid

    socialdistortionkid New Member

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    Spark plug is black and no im not going to put a bigger carb on my bike. I drilled it to a 0.72 and use 87 octane e10 gas.
     
  6. maniac57

    maniac57 Old, Fat, and still faster than you

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    The cam was wasted money if you don't set-up the engine to take advantage of the increased airflow. More power takes more fuel being burned. Simple as that. The grind of the cam matters too. Is is a high-rpm cam or a torque cam?
    Either way, airflow improvements are needed to fully exploit any performance cam. A big tubular manifold is relatively easy to make and small motorcycle carbs are fairly cheap. I'd try a small japanese bike like a Honda xr-75 or any small-bore engine of roughly the same size as a good starting point. Don't go too big, a small size increase is all thats needed with a good japanese carb. The improvement in metering and mixture control is WELL worth the hassle and expense. Don't give up now! Your potential is waiting to be unlocked!
     
  7. Greybeard

    Greybeard New Member

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    Pull off the air filter and make a run with it.
     
  8. socialdistortionkid

    socialdistortionkid New Member

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    I understand but where can i buy a manifold? I was thinking about getting a uni filter because it has a billet manifold but it wont fit because the seat post blocks it. And instead of buying another carburetor cant i just drill the main jet bigger for more fuel??
     
  9. GearNut

    GearNut New Member

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    You need a bigger carburetor to allow more air into the engine.

    A bigger hole in the fuel jet will not allow more air into the engine, only more gasoline which will upset the state of tune of the carburetor.
    Mess with the fuel jet more and you will have one heck of a krappy tuned carburetor.

    Your problem is not in the fuel delivery.
    You can drill away at the main jet until the cows come home and there is no main jet left to drill and you will still have the problem.

    Your problem is in the volume of air flow that can pass through the small throat of the stock carburetor.

    Get a carburetor with a slightly bigger throat.
    Tune the carburetor to deliver the proper fuel needs of your engine.

    Enjoy the new found power.


    Remember, a 4 stroke engine is just an air pump.
    1. Suck the air and gas in. (intake stroke).
    2. Squeeze the air and gas tightly (compression stroke).
    3. Ignite the gas and air (power stroke).
    4. Blow the spent charge out (exhaust stroke).

    What you have done is to almost allow more air into the engine which will increase the power output.
    You have a better exhaust = more exhaust out.
    You have a racing cam = higher percentage of cylinder fill potential at high RPM's.
    You will never see that potential if you have a dinky carburetor starving off the air that could be filling the cylinder.

    The carburetor just needs to be a little bit bigger.

    You may need a custom made intake manifold, or ask AGK or similar high performance MB stores about it. They may offer something that is not posted in their web store, or know of one that will suit your needs.
     
    #9 GearNut, Jan 25, 2013
    Last edited: Jan 25, 2013
  10. maniac57

    maniac57 Old, Fat, and still faster than you

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    You can easily build a manifold with some tubing, a welder and flat bar. I've done it for briggs engines for years.If you don't have a welder, you might find a muffler shop to weld it for you cheaply. Old handlebars are a good source of tubing. The main thing you have to match is the bolt spacing. You can find something in a scooter shop junk pile I'd bet...
    Whatever you do, don't go crazy. A couple mm bigger is all you need with a good japanese carb.
    Lem, cobra, Ktm, MotoMorini, Puch Yamaha, Suzuki, Honda, etc.all have small engines with possible donor carbs. Google and ebay for bargains if you can't find it locally.
     
  11. moonerdizzle

    moonerdizzle New Member

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    want a bigger carb? make a manifold and slap on a CNS like i did, but like stated before, a cam is useless with out a better carb and exhaust.
     
  12. socialdistortionkid

    socialdistortionkid New Member

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    I completely understand now. Thanks for the detailed explanation. I appreciate it.
     

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