hi i have an 06 gas gas 250 and use 70:1 mixture of putoline oil, when i open the throttle nd then shut it off quite quickly or let go of it there is a small knock noise as if the slide is hitting the bottom of the carb or something can anyone tell me what this is please??

cheers

i think that this has been a topic before but cannot find it

Well isnt it just hitting the bottom of the carb or what ever it does like its supposed to think you can hear the throttle like knocking when it returns quickly.

Track down some Tesco 99Ron or use Optimax or another 98RON fuel. If the noises disappear then you have pre-ignition.

Check out your front disc guard. They sometimes vibrate like crazy and make a rattle. I'm assuming it's not just one knock and it does sound like pinking

Edited March 15, 200620 yr by windlestone

Whats pinking sound like ?

hi i have an 06 gas gas 250 and use 70:1 mixture of putoline oil, when i open the throttle nd then shut it off quite quickly or let go of it there is a small knock noise as if the slide is hitting the bottom of the carb

I am going to assume the bike is running when this happens? It's kind of a "clack" sound...like you tapped the motor with a small hammer? If this is accurate, it's likely a lean condition at idle causing this. It is sort of "pinking", which is caused by detonation and is normally noticed most under heavy load and open throttle...sounds sort of like a bag of marbles being shaken. This too is usually a sign of a lean condition.

If the noise your hearing is similar to what I described above, I suggest you turn the fuel screw (little brass slot screw on the side of the carb) out 1/2 to a full turn and see if it improves.

thanks for your replies guys and yeh it is like u explained jtt i will try it next time im out and i use tesco fuel and its not the front disc guard knocking

If 1-2 turns on the screw doesn't fix it, pick up the next size up pilot jet. I've found I can run one richer on the pilot on every Pro I've owned.