gpx 125 problems

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lankyman

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I've got a Chinese pitbike with a gpx125 engine and when I start it it won't idle or rev for about half a minute and when riding it is coughing and spluttering what could the problem be?
 
I reckon it would be something like a dirty Carby (inside), or possibly Spark/Earth issues.
What carby is on it?
Have you pulled the carby down and given it a thorough clean out, all 3 jet's out, mixture screw out etc ?
 
I reckon it would be something like a dirty Carby (inside), or possibly Spark/Earth issues.
What carby is on it?
Have you pulled the carby down and given it a thorough clean out, all 3 jet's out, mixture screw out etc ?
Where you gettin these 3 jet carbs lol
What my67xr said sounds right though. Clean the carb out thoroughly, if that doesnt help replace your sparkplug.
 
Its a close to new 28mm molkt car by,if it helps it doesn't happen when its full throttle
 
I was thinking its too big to but I've got a mate with the same engine and carby on his bike,could the mixtures be out?
 
If your pilot jet is blocked it will give your symptoms, I know its near new but you can get carbs that are blocked from new. Remove your carb, drop the bowl off, pull your pilot and main jet out and clean the holes with some fine wire and carby cleaner. Spray the cleaner up through the jet mounts, the holes in the intake and the little hole at the rear of the carb
 
Flathead screwdriver and unscrew them. Nothing sounds stupid, everyone needs to learn mate. Best advice I can give you is spend half hour watching a couple of youtube tutorials on pitbike carbs if your not overly familiar with them, then tackle yours :)
 
I've done basic work/cleaning with carbs just havnt pulled jets just mainly quick cleans
 
There are 3 jet's in the carby Pilot Jet, Main Jet, and Needle jet (emulsion tube)

https://www.ooracing.com/store/jet-...-carbs-15-0-to-37-5-in-increments-of-2-5.html

https://www.ooracing.com/store/jet-...-dirtmax-85-180-in-2-5-or-5-0-increments.html

https://www.ooracing.com/store/needle-jet-micon/molkt/dirtmax.html


The pilot jet is the one making it hard to start and warm up, if it's not the jet then it could be the mixture screw tuning/adjustment, or a possible blockage in the pilot circuit
Has it been tuned before ?
 
There are 3 jet's in the carby Pilot Jet, Main Jet, and Needle jet (emulsion tube)

https://www.ooracing.com/store/jet-...-carbs-15-0-to-37-5-in-increments-of-2-5.html

https://www.ooracing.com/store/jet-...-dirtmax-85-180-in-2-5-or-5-0-increments.html

https://www.ooracing.com/store/needle-jet-micon/molkt/dirtmax.html


The pilot jet is the one making it hard to start and warm up, if it's not the jet then it could be the mixture screw tuning/adjustment, or a possible blockage in the pilot circuit
Has it been tuned before ?
Fair enough, I have only ever known it as the emulsion tube, and as the main jet runs through it never figured it was a "jet"so to to speak. No biggie, I was just having a joke anyways.
 
I've done basic work/cleaning with carbs just havnt pulled jets just mainly quick cleans
 
Fair enough, I have only ever known it as the emulsion tube, and as the main jet runs through it never figured it was a "jet"so to to speak. No biggie, I was just having a joke anyways.

On the Mikuni's and Oko's, Molkt's etc, the hole on the end of the needle jet/emulsion tube where the taper of the needle sits is a jet.
there are different sized jets for different set up's/tunes, just like the different sized / length / taper needles.

VM26_Rebuild_Kit.jpg
 
I've only ever done the idle speed,I'll try tuning the mixtures and see how that goes
 
I tried getting the mixtures sorted out but I just could get it running right,I also set the valve clearences and I noticed the spark plug was black so I'm starting to think the jets or the carby itself is too big
 

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