Quad bike Carby

[smith#29]

hey guys,

need some help with the old farm quad bike. its a yamaha moto 4 350. Ill start with what happen first: The bike had a bit of a rough idle and as soon as u hit the throttle it would cough and die (no matter how lightly i hit the throttle). I decided the carby hadnt been cleaned out for a while so i took it out and tore it down. soaked all the parts and the main body and blew it all out with the air (making sure all the jets and that were clear). when i was happy with it i rebuilt her back up and chucked it back in the quad. It started first go with no hesitation and idled perfect but as soon as i hit the throttle it dies straight away (if i push the throttle real lightly it will gradually pick up the revs) so i thought the A/F might be a little out so i gave it a few turns each way with still no better in throttle response. next i removed the air filter hose (which runs from the air box to the carby) which made no difference to response but when i block off the little hole (left side of the carby inlet, theres three of them left, bottom and right) it runs perfect when under throttle.

so my question is: what does this mean? have i done something wrong or what? i've tore down, cleaned and rebuilt numerous carby's with no problem like this.
so any help would be great.

cheers, and sorry for the long story i wrote lol. thanx

 

[twisties]

i dont have a huge amount of experience with bikes but maybe air/fuel ratio is out... a long way out

does it make a difference whether you have the choke on or off?

if your just bored and looknig for things to try, turn the air fuel screw all the way in (NOTE: make sure you count how many times you turned it until it stopped so you can put it back where it was if it turns out the air fuel screw isnt the problem)
then wind it back out 2.5 turns as a rough guide. if the bike runs then just make fine adjustments until your happy.

if thats not it maybe a gasket has perished and its letting air in? goodluck mate!

 

[smith#29]

cheers mate, worth a try, ill give it a go as soon as possible.

 

[smith#29]

nah mate didnt work much better, A/F screw was around 2.7 turns out so put it at about 2.5 and didnt really make a difference. Choke doesnt change how the throttle responds. kept fiddling with the screw which made no difference. checked the O rings and they look pretty good to me. got me stuffed now, dont know what else to try?

 

[minibikecr@zy]

have you checked all the fuel hoses, my mums quad (yamaha kodiak 400) was doing the same thing, me and my dad cleaned out the carby replace the inline fuel filter and bumbed up the idle, and it works fine.

 

[smith#29]

Problem Solved!!! ended up being the floats, where the valve sits on it in the middle, had a small hole/indent which would have been caused from general wear and use, this causing the float valve to get stuck at its highest point causing the carby to run dry, so just filled it up with sellys kned-it and smoothed it down and all sweet! quaddy runs beautiful now.

thanx for the help,

cheers.