blaster running poorly

[cr125fx]

ok so my friend practicly gave me this 2000 yamaha blaster becuase he couldent figure out what was wrong with it. he messed with it for a while and finally gave up and now its my headach. i have put many hours into this thing it starts up runs fine for a min or so then when i get on it it starts to bog backfire and sputter and knock and eventually dies out. i have done everything i could think of such as cleaning the jets moving the clip on the needle checking the flywheel key cleaning the wire connections removing the tors checking fuel flow and more. the choke has a problem staying out i dont think that is much of a problem and the moter seems to be hot after i run it ill let it sit for a while ill go back it will run good for a min or so and then die. when i removed the tors i cut the wires to the top of the carb and connected the ones together at the throttle. so im not sure carb or electacal. any suggestions would be greatly appreciated.

 

[Brute71]

could be that the motor/rings are worn out. Any mods that are done could help too. Checking the spark plug wouldnt be a bad idea either.

 

[cr125fx]

spark plug is brand new and has 125lbs of compression

 

[Mrbrocco]

you say it idles but doesnt go past 50% throttle?

 

[cr125fx]

no it runs ok for only about 30 seconds to a min i can go from idle to full throttle perfect i will take it up the the road get to about 3rd gear and it will jerk make knocking noises and die out i will let it sit and it does the same thing all over

 

[rrawlings]

Check and make sure you have good fuel flow to the bowl of the carb. Check the petcock and the needle and seat, if flow is slow it could be starving and refilling very slowly.

 

[cr125fx]

i checked both lol i thought the same exact thing but when i opend it up gas flowed freely when the float was down and stopped when the float was up

 

[ron89]

maybe it has a airleak and is running very lean?. how did the old plug look like the color?.

 

[2smoker85]

check your reeds? air leak, check your plug boot, air filter could be sh*t, jets could be clogged, these are all steps to take. it is time consuming but you and frustrating, i know been there, lol, take a pic of the plug and let us see the color, if it is mocha/brownish cardboard you are good, what jets are you running?

 

[cr125fx]

i have checked all of those the plug looks fine its checked all connections good spark jets are clean im not sure what the jet size but i know its stock because the whole quad is stock

 

[blaster99]

well check em again

 

[quam]

did you try disconnecting the 2 tors wires at the throttle? some models need em jumped, some need em separated.
again, let us know what the plug looked like. the spark plug will tell you everything you need to know about jetting.

 

[quam]

also, i assume the airbox lid is still on?