help! new motor dies when I give it gas

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walander

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Aug 27, 2010
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Ok, so I have been battling the chain for weeks now, finally got the chain aligned and its staying on, however, now I cant get it started, its a grubee gt5, It only starts when I have the choke wide open ( when its closed I cant get it to start at all ) If I peddle like mad and drop the clutch, it starts, but it wont idle unless im peddling and if I give it some throttle, it gives me a 3 second burst of power then it chokes out and dies, whats wrong here? any help would be great, thanks
 

2door

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Sep 15, 2008
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Why are you trying to run it with the choke on (closed)?
Any engine will die if it can't get air. If you don't have any air leaks in the induction system, carburetor, intake manifold, etc, then the engine will not run with the choke on.
All of these little 2 strokes seem to like different approaches to starting. Some like a lot of choke, some won't tolerate any. Try starting with the choke off, (lever down) and see what happens. Maybe half choke is the secret with your particular engine. The choke is only used for starting, if needed, then after a few seconds of run time the choke should be opened completely...and left open.
As for other reasons for not starting keep in mind you need three things: Fuel, air and an ignition source. Confirm you have all three then get back to us if you still have problems.
Tom
 

walander

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Aug 27, 2010
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Ok, As I said, its running with the choke OPEN, not trying to run it closed ( and I have the high performance carb with the choke lever on the handle bars) but anyways got it running ( carb had been knocked at an angle, straightened it out, now it runs. however, it ran for a mile or so, when it shut of, it was smoking grey smoke from the exaust pipe, ran it again a few hours later, it now runs like crap, sputters and hardly moves at all, and now no more smoke, the smoke meant it was running rich right? should I change my oil to fuel ratio? I had 16:1 then read that you should run 32:1 for break in, so I changed it, was it running the old 16:1 through the line and started running like crap after it started sucking in the new 32:1 ratio? should I add more oil again?
 

Allen_Wrench

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Feb 6, 2010
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Ok, As I said, its running with the choke OPEN, not trying to run it closed ( and I have the high performance carb with the choke lever on the handle bars) but anyways got it running ( carb had been knocked at an angle, straightened it out, now it runs. however, it ran for a mile or so, when it shut of, it was smoking grey smoke from the exaust pipe, ran it again a few hours later, it now runs like crap, sputters and hardly moves at all, and now no more smoke, the smoke meant it was running rich right? should I change my oil to fuel ratio? I had 16:1 then read that you should run 32:1 for break in, so I changed it, was it running the old 16:1 through the line and started running like crap after it started sucking in the new 32:1 ratio? should I add more oil again?
I've started to wonder how your needle valve is set. As I'm guessing you already know, the throttle cable moves the needle valve up and down, increasing or decreasing the air-fuel mix headed for the combustion chamber, This needle valve has a C-clip at the top, and notches in it for clipping the C-clip further up or down. Many of us put the C-clip in the second notch from the top end of the needle valve, if it does not come that way. May I ask, where is yours clipped?
 

walander

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Aug 27, 2010
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I've started to wonder how your needle valve is set. As I'm guessing you already know, the throttle cable moves the needle valve up and down, increasing or decreasing the air-fuel mix headed for the combustion chamber, This needle valve has a C-clip at the top, and notches in it for clipping the C-clip further up or down. Many of us put the C-clip in the second notch from the top end of the needle valve, if it does not come that way. May I ask, where is yours clipped?
ok, so I changed the c-clip to the second notch to the top, it helped, however, I find that I have to have the throttle at just the right spot ( not full, maybe half) for the engine to run right, if I give it to much or to little gas, it starts to sputter, also, it tends to break up and sputter at higher speeds, change the c-clip again?
 

Allen_Wrench

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Feb 6, 2010
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ok, so I changed the c-clip to the second notch to the top, it helped, however, I find that I have to have the throttle at just the right spot ( not full, maybe half) for the engine to run right, if I give it to much or to little gas, it starts to sputter, also, it tends to break up and sputter at higher speeds, change the c-clip again?
It COULD be that it's just still breaking in, but somehow I think there's more to this. If only I could be right there to watch it run, I'd probably go "Oh, I know what it is - here, watch this!" But it's harder, diagnosing MB quirks this way. I imagine better experts than myself will chime in soon (I hope).
 

walander

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Aug 27, 2010
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The other thing I have noticed with it is that when I shut of the fuel valve, and run the fuel out of the line, it goes like a bat out of heck a minute or so before the gas runs out, why is this? any one know?
 

Allen_Wrench

Resident Mad Scientist
Feb 6, 2010
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The other thing I have noticed with it is that when I shut of the fuel valve, and run the fuel out of the line, it goes like a bat out of heck a minute or so before the gas runs out, why is this? any one know?
Okay, well, now we know there's a fuel uptake problem somewhere in the system but, whatever you do, PLEASE don't keep running her out of fuel. It's bad, bad, bad, bad, bad, for the engine. Other members here have warned about it too, and it makes sense. The fuel has the engine's lubrication in it. Running her dry means she runs out of lube just before she dies. It's a bit harsh.
 

walander

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Aug 27, 2010
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Okay, well, now we know there's a fuel uptake problem somewhere in the system but, whatever you do, PLEASE don't keep running her out of fuel. It's bad, bad, bad, bad, bad, for the engine. Other members here have warned about it too, and it makes sense. The fuel has the engine's lubrication in it. Running her dry means she runs out of lube just before she dies. It's a bit harsh.
Noted, thank you for the warning. I have been reading on here that it could be an air leak causing it to sputter, Now, I have this high pro carb http://www.gasbike.net/bike-motor-engine-high-performance-carburetor.html it has all those tubes comming off of it, it says to leave them free, but should I plug them? what do they do? also, gas slowley drips from the hose near the bottom of the carb, if gas is comming out, could air not be going in? I didnt order the carb, but they sent it anyway ( its a $20 add on to my kit, so im not complaining)
 

Allen_Wrench

Resident Mad Scientist
Feb 6, 2010
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Noted, thank you for the warning. I have been reading on here that it could be an air leak causing it to sputter, Now, I have this high pro carb http://www.gasbike.net/bike-motor-engine-high-performance-carburetor.html it has all those tubes comming off of it, it says to leave them free, but should I plug them? what do they do? also, gas slowley drips from the hose near the bottom of the carb, if gas is comming out, could air not be going in? I didnt order the carb, but they sent it anyway ( its a $20 add on to my kit, so im not complaining)
That's a carburettor I'm not familiar with. HEY everybody! We may need the help of somebody who has one of these carburettors, I've seen where they've been finagled into working condition, but I don't know how myself. Thanks guys.
There, we'll see who chimes in. I know there are other people with those things. They'll take care of you.
 

FreeWheeler

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Jun 22, 2010
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The other thing I have noticed with it is that when I shut of the fuel valve, and run the fuel out of the line, it goes like a bat out of heck a minute or so before the gas runs out, why is this? any one know?
Runs like heck because it runs lean just before it dies out. Lean running is the devil you want to keep out of your engine. Your plug will tell you if youre running lean as a general condition. Intermittent fuel starvation will cause a brief lean condition, as it dies, which the plug might not indicate. Still, check the plug.


Search for CNS carb and read everything you can, even stuff which seems unrelated. Someone has had the same problem somewhere and even if not exact it could give clues.
 

FreeWheeler

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Jun 22, 2010
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One more thing, if you look at the pictures of the carb. The line near the air filter is shown as looped into the other nipple on the other side carb. That doesnt mean it is right, but it contradicts the first picture which says disconnect(free). They only show one line hanging loose which is the one on the bottom. I'd follow the pictures. Also, if you look at other bikes with the CNS carb, see if you can see those lines.
 

walander

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Aug 27, 2010
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Ok, so funny thing, I sold that bike and got another bike and kit, and it does the same thing, well, sort of, the c clip is on the second notch from the top, I have to run it with the choke at half for about a mile or two and at half throttle, If I go WOT, it cuts out and dies, bogs down, after a mile or so I can the open the choke all the way and it will then have no power on the low end, but I can then run it WOT, what the heck?!!