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Thread: 125cc Carb on 70cc

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    Default 125cc Carb on 70cc

    Yesterday i brought a new 125cc future carb and put it on my stock 70cc on stock mainfoild and removed the airbox.
    But it was too rich on fuel, there was black carbon on spark plug.
    I did every thing to reduce its fuel to air ratio, e.g. that adjuster screw beneath the carb, float height. but useless.
    The stock jets in that carb are 88 and 38 lable.
    now i don't know why is it too rich on fuel ratio? and how to reduce that ?

    ------------------------------------ALTERATION/MODIFICATION SEPARATE HUMAN FROM BEAST-----------------------------------------

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    amazingly no one yet
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    i am not a expert but its simple you are putting a cg carb and its jets are bigger for small 70cc bike which is half the size of cg so u needs a carb of 70 which is mada for 70cc bike

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    its sucking air accordingly isn't it !
    you may be right thats why i was also thinking of my custom built mainfold for that, lets see if this help a bit, IF it did help than the next part will be increasing combustion chamber size etc.
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    My younger brother has installed a CG carb on a Chonda 78cc....... works fine. We got the mixture setting right quite easily on my brother's bike..... the spark plug tip came out chocolate brown.

    You have done everything which I could think of with the carb....... I really am not sure whats going wrong...... or just maybe I do

    Do you have any sort of air filter on it currently. Maybe you are sucking way too much air..... venturi of CG carb is obviously bigger...... try restricting the air flow... either use a air filter or cover up half of the carb's venturi with some electric tape.

    You might think....Im already running rich..... why the hell should I restrict the air even further ......... try it plz....... if it works I'll tell you my theory behind this advice. You have to try it first!
    Bikes don't leak oil, they mark their territory.

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    Some pics of newly brought carb

    125cc Carb on 70cc -1411408125cc Carb on 70cc -1411409125cc Carb on 70cc -1411411125cc Carb on 70cc -1411412125cc Carb on 70cc -1411413125cc Carb on 70cc -1411414125cc Carb on 70cc -1411415125cc Carb on 70cc -1411417125cc Carb on 70cc -1411418125cc Carb on 70cc -1411419125cc Carb on 70cc -1411421125cc Carb on 70cc -1411422125cc Carb on 70cc -1411424125cc Carb on 70cc -1411425
    ------------------------------------ALTERATION/MODIFICATION SEPARATE HUMAN FROM BEAST-----------------------------------------

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    Okay aximaximi will try experimenting with this, it will suck less air so less fuel gets in !

    how to get it lean, turning inwards or outwards ?
    ------------------------------------ALTERATION/MODIFICATION SEPARATE HUMAN FROM BEAST-----------------------------------------

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    Quote Originally Posted by Fahd150 View Post
    Okay aximaximi will try experimenting with this, it will suck less air so less fuel gets in !

    how to get it lean, turning inwards or outwards ?
    Clockwise rotation = richer mixture
    Anticlockwise rotation = leaner mixture.

    I cant remember which one but either amjad635 or asjdsm did a great write up on how to tune carb.
    I tried but was unable to find the post.
    Maybe they can help with your issue.
    Bikes don't leak oil, they mark their territory.

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    first make sure that the carb bend is flush with the carb venturi and inlet manifold.

    buy qingqi cd100 rickshaw manifold from pirwadahi. then use any drill machine with grinding stones to increase and match the inner of the bend pipe to the sizes .

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    Trust me, carb ke sath joogrd karny se koi farq nai parta, its just this eras's trend to jo manjan with chonda's engine and carb. speed come with engine's specs. good fuel average comes with original carb.

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    @ asjdm yes it is flush and bolt on fit.
    i have a planed to use a water pipe fitting bend which is biggest in diameter and both the end part will be made by kharidia than i will weld them together to make a main fold !
    but i will also visit pirwadahi.
    ------------------------------------ALTERATION/MODIFICATION SEPARATE HUMAN FROM BEAST-----------------------------------------

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    Clock wise rotation = lean mixture.
    Nothing can be done to reduce fuel ration in mixture.

    I ride it today without air filter and air box. It was accelerating very smoothly on 15-38 sprockets and it wasn't feeling any load while shifting gears but in 4th gear there was a little bit decline in acceleration. just to guess the effect of new bigger carb i compete with few 125cc and amazingly it beat them in first 3 gears with a margin of 5-8 meters. But it 4th gear they merely passed me or it was giving them a fight in forth.

    so altho this carb is very rich in fuel but it is very power full next step will be to put a larger diameter bend and con filter and replace ideal jet with a smaller one. current jets are labeled 34 and 88 because on current rich mixture it is impractical.
    ------------------------------------ALTERATION/MODIFICATION SEPARATE HUMAN FROM BEAST-----------------------------------------

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    Quote Originally Posted by Fahd150 View Post
    Clock wise rotation = lean mixture.
    Nothing can be done to reduce fuel ration in mixture.

    I ride it today without air filter and air box. It was accelerating very smoothly on 15-38 sprockets and it wasn't feeling any load while shifting gears but in 4th gear there was a little bit decline in acceleration. just to guess the effect of new bigger carb i compete with few 125cc and amazingly it beat them in first 3 gears with a margin of 5-8 meters. But it 4th gear they merely passed me or it was giving them a fight in forth.

    so altho this carb is very rich in fuel but it is very power full next step will be to put a larger diameter bend and con filter and replace ideal jet with a smaller one. current jets are labeled 34 and 88 because on current rich mixture it is impractical.
    I think the loss in power in the 4th gear is bcoz the engine is not producing enough torque for altered sprockets you have installed. The issue of rich mixture is another issue altogether. Have you tried restricting the air flow?
    Bikes don't leak oil, they mark their territory.

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    restricting air flow DO NOT WORK.

    It is not actually power loss, the power is spread over long 4th gear.

    I will change gets then it will work fine ideal jet is more troublesome.
    ------------------------------------ALTERATION/MODIFICATION SEPARATE HUMAN FROM BEAST-----------------------------------------

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    125cc Carb on 70cc -1414298
    ------------------------------------ALTERATION/MODIFICATION SEPARATE HUMAN FROM BEAST-----------------------------------------

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    hi @asjdsm i want to increase some acceleratoin n top speed in cd 70, what modification i can do on carb jets i got on spare carb, so want to experiment on that, i notices jet no. was 35, in both cd 70 carbs, but there was holes size difference, like bigger jet cylinder holes were big, but smaller jet was samller, while one other carb bigger jet holes was smaller, and smaller holes was bigger...
    secondly as advised by @aximaxim i am using 16-41 sprocket for cd 70. model is 2006.

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    Quote Originally Posted by ars.gha View Post
    hi @asjdsm i want to increase some acceleratoin n top speed in cd 70, what modification i can do on carb jets i got on spare carb, so want to experiment on that, i notices jet no. was 35, in both cd 70 carbs, but there was holes size difference, like bigger jet cylinder holes were big, but smaller jet was samller, while one other carb bigger jet holes was smaller, and smaller holes was bigger...
    secondly as advised by @aximaxim i am using 16-41 sprocket for cd 70. model is 2006.


    Try this link may be it can help, I am facing the same thing but I guess Acceleration and Top Speed both cannot be attained at the same time.

    Adjusting Your Drive Ratio - Changing Your Sprockets for Maximum Performance - Chaparral Motorsports

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    125cc Carburetor in a 70cc Motorcycle...???

    WOW!!! AMAZING!!! Now we don't need to buy a CG125 cause we can make our CD70s as fast as a CG125, LOLz...!!!

    Sorry to say; but our "AWAM" need a little knowledge about engines and their working principal...

    There's a reason why one can't run a car on bloody DISTILLED WATER LOLz...!!! The reason is simple; "You can't bend laws of physics"...

    It's not THE MATRIX & you're definitely not NEO...!!! It's the UNIVERSE and everything has a principal!

    Allow me to elaborate:To make more power; you need a bigger EXPLOSION!!! BIGGER BOOM in the cylinder!!!And for that you need bigger combustion chamber, bigger piston, bigger air port, bigger valves to let more air in the combustion chamber, stronger crankcase, chassis & transmission and etc etc to name a few...

    You can't just feed more fuel into the chamber and hope that it'll beat a YAMAHA R1, Ha! It won't 'make' more power, although it'll definitely make more 'smoke' because of wasted un-burnt fuel...

    Do you want smoke?

    So instead of your cute little experiments; learn about engines first and then ask yourself whether it'll make any difference??? I mean, its Plain Logic!

    Have a nice day!

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    Quote Originally Posted by k-four-nine View Post
    125cc Carburetor in a 70cc Motorcycle...???

    WOW!!! AMAZING!!! Now we don't need to buy a CG125 cause we can make our CD70s as fast as a CG125, LOLz...!!!

    Sorry to say; but our "AWAM" need a little knowledge about engines and their working principal...

    There's a reason why one can't run a car on bloody DISTILLED WATER LOLz...!!! The reason is simple; "You can't bend laws of physics"...

    It's not THE MATRIX & you're definitely not NEO...!!! It's the UNIVERSE and everything has a principal!

    Allow me to elaborate:To make more power; you need a bigger EXPLOSION!!! BIGGER BOOM in the cylinder!!!And for that you need bigger combustion chamber, bigger piston, bigger air port, bigger valves to let more air in the combustion chamber, stronger crankcase, chassis & transmission and etc etc to name a few...

    You can't just feed more fuel into the chamber and hope that it'll beat a YAMAHA R1, Ha! It won't 'make' more power, although it'll definitely make more 'smoke' because of wasted un-burnt fuel...

    Do you want smoke?

    So instead of your cute little experiments; learn about engines first and then ask yourself whether it'll make any difference??? I mean, its Plain Logic!

    Have a nice day!
    Compression is an unknown word for Desi mechanics some will actually tell you a worn engine produce more torque lol btw a carb with bigger inlet port will make bike suffer from pumping losses and this thing is totally ignored by Desi mechanics

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    Quote Originally Posted by ars.gha View Post
    hi @asjdsm i want to increase some acceleratoin n top speed in cd 70, what modification i can do on carb jets i got on spare carb, so want to experiment on that, i notices jet no. was 35, in both cd 70 carbs, but there was holes size difference, like bigger jet cylinder holes were big, but smaller jet was samller, while one other carb bigger jet holes was smaller, and smaller holes was bigger...
    secondly as advised by @aximaxim i am using 16-41 sprocket for cd 70. model is 2006.
    Bro carb is used to feed air and fuel mixed in specific ratio and specific quantity in specific amount of time.
    70 cc carb are tuned for performance and don't need any change at average working conditions.

    125 carb had bigger venturi compared to 70. So it won't create perfect turbulence in cylinder.

    Moreover there is dire shortage of needle jets availability in local market so that one can tune the carb.

    Since it's venturi is bigger so you will have to widen the inlet port too, while you have extra carb you won't have extra cylinder head.

    You can use the k&n style free flow filter and it will give best results in terms of acceleration and speed.

    I m using it with my alter bike for the past 4 years. And I haven't changed it yet. I only clean it.


    Quote Originally Posted by k-four-nine View Post
    125cc Carburetor in a 70cc Motorcycle...???

    WOW!!! AMAZING!!! Now we don't need to buy a CG125 cause we can make our CD70s as fast as a CG125, LOLz...!!!

    Sorry to say; but our "AWAM" need a little knowledge about engines and their working principal...

    There's a reason why one can't run a car on bloody DISTILLED WATER LOLz...!!! The reason is simple; "You can't bend laws of physics"...

    It's not THE MATRIX & you're definitely not NEO...!!! It's the UNIVERSE and everything has a principal!

    Allow me to elaborate:To make more power; you need a bigger EXPLOSION!!! BIGGER BOOM in the cylinder!!!And for that you need bigger combustion chamber, bigger piston, bigger air port, bigger valves to let more air in the combustion chamber, stronger crankcase, chassis & transmission and etc etc to name a few...

    You can't just feed more fuel into the chamber and hope that it'll beat a YAMAHA R1, Ha! It won't 'make' more power, although it'll definitely make more 'smoke' because of wasted un-burnt fuel...

    Do you want smoke?

    So instead of your cute little experiments; learn about engines first and then ask yourself whether it'll make any difference??? I mean, its Plain Logic!

    Have a nice day!

    Sent from my Nexus 5 using Tapatalk

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