engine sputters and sounds like it's going to die

GoldenMotor.com

2tontarantula

New Member
Dec 4, 2012
9
0
0
Las Vegas NV
I had a prev issue with the CDI and was able to fix it by installing a new CDI. However. I took a long ride a couple of days ago and notice midway that the engine sounded like it was dying, like lack of gas sounds or I left the choke on. When I got home I noticed that my choke was on just a bit and thought that was the issue. I took it out for a ride today and that was not the case. I made sure the choke was all the way off once the bike was warmed up.
When I would floor it, the bike would accelerate for a couple of seconds and then it would start to sputter and lose power. I'm sort of new to the 2 stroke scene and don't know if this is just what happens when you floor it or if this is something I can fix. any and all help would be greatly appreciated.
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Start by assuring that you have good fuel flow from the tank to the carburetor. Pull the fuel line from the carb and open the fuel petcock. You should see a steady flow of fuel. It doesn't need to look like a fire hose but it should run a steady stream and not drip. If you don't have a steady stream the in-tank fuel filter might be clogged. We always suggest that a new tank be flushed and cleaned before installation and that an in-line fuel filter be installed between the tank and the carburetor.

Second, check you fuel tank cap for venting. Many have had problems with the cap that will not allow the tank to vent and the engine will starve for fuel do to a vacuum created in the tank which is unable to vent to the atmosphere. Try loosening the cap and riding and see if that cures your problem.

Let us know what you find.

Tom
 

biknut

Well-Known Member
Sep 28, 2010
6,631
409
83
Dallas
Fuel venting, or lack of, is a common problem as Tom mentions above. Usually the symptom is, it runs well for about 1/4 mile, and then dies like it's out of gas. If you loosen the gas cap to relieve the pressure, and if runs fine after that, it's probably a venting problem caused by the cap not having a vent hole.

If it turns out not to be that, another good suspect is the magneto coil. It can fail and act almost exactly like a fuel problem, where it starts fine cold, but as it warms up it can sputter a little and die. CDI modules don't fail very often, but the mag coil doesn't fare as well because of the stock kill switch being used to short the coil windings out to kill the ignition.

You can check the magneto coil with an ohm meter. You should read about 35 ohm between the blue and black wires on the mag coil when the CDI is disconnected.
 

2tontarantula

New Member
Dec 4, 2012
9
0
0
Las Vegas NV
the bike runs fine and I've riden it for over an hour. Not once did it die. My issue is just when I give the gas too much throttle/gas the engine sounds like it will die but it doesn't cause I throttle down at that point and the bike runs normally. It's just when I seem to go over a certain point. The engine sputters loses some power. When I let go of the throttle or throttle down the bike behaves like normal.
 

biknut

Well-Known Member
Sep 28, 2010
6,631
409
83
Dallas
That sounds like bogging. That can be caused by running rich. How's the idle? How loud is the exhaust?
 

larry57

New Member
Mar 20, 2012
20
0
0
st james ctiy ,fl
what kind of carb you running ,,i had the same problem with the CNS hi-pref,carbs ,,there junk ,,don't think there really matched to the motor ,,i have 3 i can't give away
 

2tontarantula

New Member
Dec 4, 2012
9
0
0
Las Vegas NV
thanks so much for all the advice. Unfortunately I've got Christmas obligations before I can play with my toys. I will try to sneak out for a bit and check some of the stuff out. Merry Christmas/Kwanzaa/Hanuka!!!
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Keep in mind that the needle only controls fuel flow from idle to about 3/4 throttle. Anything above that is controlled by the main jet orifice size. If you're bogging at wide open throttle it isn't because of needle or 'C' clip location.

How many miles/gallons of fuel on this engine? Until you've burned at least two gallons I wouldn't worry too much about how the engine performs. They all gain power as they accrue milage. New engines, or ones that are not broken in never perform to their full potential.

What fuel/oil ratio are you running?
What is your spark plug gap?

Tom
 

2tontarantula

New Member
Dec 4, 2012
9
0
0
Las Vegas NV
Seems that I just killed my engine. I checked the needle to see what the clip setting was on and thought I put it back together properly. When I started my bike it (without the choke on) it started right away but sounded like the throttle was stuck all the way on. and I was speeding up really fast. Right about the same time I hit the shut off button there was an ugly crunch sound and I heard something fall off the bike. Once stopped I looked down and my choke lever was gone. Could not get the bike started again because now it seems like the engine is not even turning from the sound of it or lack of sound coming from it. Once I pedaled it back home and checked some more stuff I noticed that my spark plug boot was loose. I pulled it off the spark plug and it fell apart. So now I guess I have a worse problem than before. I think I may need to buy another engine unless anyone thinks I can salvage what I've done to it.
 

2tontarantula

New Member
Dec 4, 2012
9
0
0
Las Vegas NV
At this point the only thing I do have that I can replace is the spark plug boot. I know I'm gonna have to pull the engine apart to see what the damage is unless anyone has a better idea. Other than giving up and buying a moped. I would rather get dirty repairing this bike than resort to getting a moped.
 

biknut

Well-Known Member
Sep 28, 2010
6,631
409
83
Dallas
Seems that I just killed my engine. I checked the needle to see what the clip setting was on and thought I put it back together properly. When I started my bike it (without the choke on) it started right away but sounded like the throttle was stuck all the way on. and I was speeding up really fast. Right about the same time I hit the shut off button there was an ugly crunch sound and I heard something fall off the bike. Once stopped I looked down and my choke lever was gone. Could not get the bike started again because now it seems like the engine is not even turning from the sound of it or lack of sound coming from it. Once I pedaled it back home and checked some more stuff I noticed that my spark plug boot was loose. I pulled it off the spark plug and it fell apart. So now I guess I have a worse problem than before. I think I may need to buy another engine unless anyone thinks I can salvage what I've done to it.
If you choke lever fell off then the crunching sound you heard was probably the nut that holds the lever on getting eaten by the motor. Take the air cleaner off and look for it there first. If it's nowhere in sight, remove the cylinder head and look in there.
 

SpeedWizzard

New Member
Mar 9, 2012
93
0
0
Australia
first off your motor probably isn't ruined. and also try checking the exhaust, quite often there is a large piece of slap or defect blocking off the exhaust that oculd severly limit power output.
 

2tontarantula

New Member
Dec 4, 2012
9
0
0
Las Vegas NV
Tom,
I've not gone through one gallon yet. I was informed by the seller that the engine was already broken in and that I use a 50:1 ratio for fuel/oil. I don't have a gap thingy yet to check the spark plug gap but will get one.
Though now my problem is I think the nut that holds the choke lever in place got eaten by my engine when the throttle got stuck. (from me checking to see what the clip on the needle was set at). I don't think I put it back together properly as when the bike started it sounded like it was going full throttle until I hit the kill switch. At the same time there was a crunchy noise and I noticed my choke lever was gone. I found the lever and as stated by another post that the nut for this may have been sucked into the engine. Gonna pull the carb off to see if it's there and then move to the cylinder if it's not.
Do you think that the nut being in the cylinder would keep the engine from turning? Because I did try to start it again after the crunch and it does not turn over.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
Tom,
I've not gone through one gallon yet. I was informed by the seller that the engine was already broken in and that I use a 50:1 ratio for fuel/oil. I don't have a gap thingy yet to check the spark plug gap but will get one.
Though now my problem is I think the nut that holds the choke lever in place got eaten by my engine when the throttle got stuck. (from me checking to see what the clip on the needle was set at). I don't think I put it back together properly as when the bike started it sounded like it was going full throttle until I hit the kill switch. At the same time there was a crunchy noise and I noticed my choke lever was gone. I found the lever and as stated by another post that the nut for this may have been sucked into the engine. Gonna pull the carb off to see if it's there and then move to the cylinder if it's not.
Do you think that the nut being in the cylinder would keep the engine from turning? Because I did try to start it again after the crunch and it does not turn over.
If your engine ingested any solid object, nothing much good can happen. Pull the head and cylinder to find the damage.
A whole new top-end for these motors is fairly cheap, don't give up too soon!
 

SpeedWizzard

New Member
Mar 9, 2012
93
0
0
Australia
it would do no good at all but shouldn't stom the motor completly from turning over in one direction or the other until it hits TDC, you may have seized it or had a bearing failure running at 50:1, I highly doubt you dd but it's not too uncommon on these engines at 25:1 so i'm not sure. Hope you find the problem!
 

2tontarantula

New Member
Dec 4, 2012
9
0
0
Las Vegas NV
I checked the carb and the nut for the choke was not there as I thought. I pulled the cylinder off and there were pieces of the nut all in there. The nut got chewed up into little pieces and is all over the inside of the cylinder. I think some of it fell in the rest of the engine jamming up the gears. At this time the engine is still on the bike. I've never taken one of these apart before and was wondering if I need to take the engine off the bike just to clean out the bits. The piston is pretty gouged out as well from where the nut gut sucked into it. So I suppose I need to replace that as well. Suggestions for this noob would be extremely helpful. .shft.
 

biknut

Well-Known Member
Sep 28, 2010
6,631
409
83
Dallas
I checked the carb and the nut for the choke was not there as I thought. I pulled the cylinder off and there were pieces of the nut all in there. The nut got chewed up into little pieces and is all over the inside of the cylinder. I think some of it fell in the rest of the engine jamming up the gears. At this time the engine is still on the bike. I've never taken one of these apart before and was wondering if I need to take the engine off the bike just to clean out the bits. The piston is pretty gouged out as well from where the nut gut sucked into it. So I suppose I need to replace that as well. Suggestions for this noob would be extremely helpful. .shft.
I'll tell you the truth, you might as well get a new motor. Use the one you've got for parts.
 

Fugi93

New Member
Dec 30, 2011
144
0
0
illinois
the bike runs fine and I've riden it for over an hour. Not once did it die. My issue is just when I give the gas too much throttle/gas the engine sounds like it will die but it doesn't cause I throttle down at that point and the bike runs normally. It's just when I seem to go over a certain point. The engine sputters loses some power. When I let go of the throttle or throttle down the bike behaves like normal.
I just had that happen on my Hs 49cc. Only a little more severe. I finally blew into the right side epa tube and that fixed it. Thank you, Lord!