Carby NT Carb Tuning Basics

lewsidius

Member
Joined
Jun 10, 2011
Messages
42
hello everyone
my engine starts but the bike doesnt take off
i move the throttle open and no change in sound
and i slowly come to a hault and the engine turns off
the engine has a good sound and a consistent rythum
i tried the bike before work after tightening the Throttle

the bike idles then as i lose speed the engine gets quiter and i slowly come to a hault

i took apart the carb and the slide is moving proper back and forth
and the spark plug definatly has a strong spark (ouch)
thanks
chris

so i dont know what to adjust or whats wrong????

hello again
i adjusted the float
and gas is leaking
but i started the bike anyway
and it actually moved
its stupid i know
but i was able to go pretty fast
and i wanted to see if it worked and it did
however it really over heated

but its helped me establish that there is a shortage of gas going in

it either barely gets enough gas and just idles
or it gets too much gas and doesn't idle but it takes off and overheats

and i only move the forks on the float ever so slightly to make this transition

when i look at the gas line when there is not enough gas it fills just to the bottom of the filter on the line

and when its overflowing
that when the entire line is full

help?
im so close
thanks!


i currently have a separate thread on the matter (sorry) i just wanted to reach a bigger audience


http://www.motoredbikes.com/showthread.php?t=34637
 


SdCruizer

Member
Joined
Jan 29, 2012
Messages
107
I just put on a bolt on larger filter k&n style
I also bought 2 jets 72, 74
Ive jetted a carb before on a scooter and knew when it was too large by the bogging at full throttle but I had more jets on hand and purposly started too large

when I tried the 74 it ran fine, just seemed to loose top speed or didnt get to full speed quick enough hard to determine going up hills
72 seems normal how I remember the stock setup felt like

I will check the plug but I was wondering I read once about a tool you can use to check jet sizes, I think they were pins or something

I want to compare the new jets to the stock jet hole

Someone posted they ran a pipe and same filter and used the 74 jet, which makes me think my 72 at the least will be fine
Since its a pain to change I never tried the stock jet
 

sekeisman1275

New Member
Joined
Feb 23, 2012
Messages
3
Bogs down uphill

I just bought a 49cc Chinese bicycle engine and I have it mounted to the frame of a Schwinn mountain bike. It is running well, but I can't seem to figure out if I have the air/fuel mixture figured out properly. I have adjusted the clip on the pin at every level and noticed a difference for each setting. I currently have it set to the leanest clip setting (1st notch) and it runs fairly well.

I know that most people say that it runs best on the second notch, but when I set it to 2nd notch the engine would bog down when I would rev the throttle quickly, and it would also 4-stroke at 80% throttle. I have taken the whole carburetor apart and checked to make sure the float was level.

The problem that I am having is that my bike has very little power when it is going up any incline at all. It does great on level ground and down-hill, but when I am facing any kind of up-hill grade it slows down significantly. I can have the throttle at 100% and I cannot feel it rev up. While going uphill it either revs down (if the hill is serious) or it stays at a mid rev sound (I'm sorry I don't know how to explain it with proper terms). Is this normal for the bike to suck so much uphill, or should I be getting some acceleration uphill on small hills? Thank you for any advice and assistance.
 
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happycheapskate

Active Member
Joined
Nov 5, 2009
Messages
1,389
I have a 49cc, with a 36 tooth cog, on a heavy beach bike. It will pull my 140lb butt and some cargo up overpasses and similar grades, as long as it was moving over 20 when I got there, not much grunt under 20mph with the small cog.

It pretty much sucked until break-in. You'll know when it gets there.
 

SdCruizer

Member
Joined
Jan 29, 2012
Messages
107
I just bought a 49cc Chinese bicycle engine and I have it mounted to the frame of a Schwinn mountain bike. It is running well, but I can't seem to figure out if I have the air/fuel mixture figured out properly. I have adjusted the clip on the pin at every level and noticed a difference for each setting. I currently have it set to the leanest clip setting (1st notch) and it runs fairly well.

I know that most people say that it runs best on the second notch, but when I set it to 2nd notch the engine would bog down when I would rev the throttle quickly, and it would also 4-stroke at 80% throttle. I have taken the whole carburetor apart and checked to make sure the float was level.

The problem that I am having is that my bike has very little power when it is going up any incline at all. It does great on level ground and down-hill, but when I am facing any kind of up-hill grade it slows down significantly. I can have the throttle at 100% and I cannot feel it rev up. While going uphill it either revs down (if the hill is serious) or it stays at a mid rev sound (I'm sorry I don't know how to explain it with proper terms). Is this normal for the bike to suck so much uphill, or should I be getting some acceleration uphill on small hills? Thank you for any advice and assistance.


heres a stupid idea, but check the plug gap
my stock came set at 50 and while it worked just fine I put in a new plug after break in and copied the gap at 50 and it struggled up hills, but flat ground it was fine

maybe your plug is fouling who knows but check it out

any changes your making with the needle may change once you break in and change the mixture
whats your ratio at now?
 
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sekeisman1275

New Member
Joined
Feb 23, 2012
Messages
3
So I changed my plug wire and my spark plug. I am using a NGK bp5hs plug with a gap of .030 but it seems that my bike is still having the same problems.

Additionally, after I warm up the engine and have it sitting still at an idle if I try to crank the throttle to get it to rev up from a stand still it totally kills the engine. I will twist the throttle grip at an idle and It sounds like it bogs really low and then it just dies. I have tried this on every needle setting and it seems to have less problems when the needle is at the 1st notch (top position), but it isn't any significant difference.

Also, my ratio on oil/gas is 16:1 because it is the second tank of gas I'm running through.
I am not getting any kind of good mpg by the way. I went through my first tank and only got like 40-50 miles on the whole tank.
 

bms420

New Member
Joined
Mar 11, 2012
Messages
5
no matter what I try I can't get mines to stop 4stroking.... I have the C clip at the very top less four stroking but still there even more the lower I go..... Help!
 

happycheapskate

Active Member
Joined
Nov 5, 2009
Messages
1,389
Have you tried checking your fuel filter? (disconnect the line from the carb, into a jug, and see if it flows freely.) Also a good time to see if your fuel cap is venting. (do the same thing, if it is not flowing, and open the gas cap a little. If flow speeds up rapidly, its the cap). Be safe. Don't spill gas on the engine or ignition, and be ready to plug/crimp the fuel line, move it to a gas can, or shut off the fuel valve.

Using thick oil or a lot of oil can clog up some fuel filters, especially paper ones not made for gravity feed lines or for mix-fuel.

So I changed my plug wire and my spark plug. I am using a NGK bp5hs plug with a gap of .030 but it seems that my bike is still having the same problems.

Additionally, after I warm up the engine and have it sitting still at an idle if I try to crank the throttle to get it to rev up from a stand still it totally kills the engine. I will twist the throttle grip at an idle and It sounds like it bogs really low and then it just dies. I have tried this on every needle setting and it seems to have less problems when the needle is at the 1st notch (top position), but it isn't any significant difference.

Also, my ratio on oil/gas is 16:1 because it is the second tank of gas I'm running through.
I am not getting any kind of good mpg by the way. I went through my first tank and only got like 40-50 miles on the whole tank.
 

happycheapskate

Active Member
Joined
Nov 5, 2009
Messages
1,389
Try another spark plug, too, esp a known good one with a lesser gap. I ran a champion lawnmower plug for a while, on a happytime. It ran ok once the engine was good and warmed up, then ran a little hot, but the engine sputtered and was temperamental until then.
 

tooljunkie

Member
Joined
Apr 6, 2012
Messages
110
i resized my carb jet from a 70 (.028") down to a 74(.0225").
still four stroking,needle is on top groove.
i put the jet into a cordless drill,and held the number drill in my pin vise.drilled out easily.
my pin vise is a tip drill used for cleaning cutting torch tips.
 
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