OzVMX Forum

Clubroom => Tech Talk => Topic started by: zman on August 23, 2009, 05:47:48 pm

Title: carby headache
Post by: zman on August 23, 2009, 05:47:48 pm

gday ive got an 82rm250 that wont idle at all my mechanic said there not meant to ???. but im sure they did when they were new anyway it has standard jetting 60-300 and the motor is in good nic with no air leaks the clip 2nd pos from the top. should i turn the air screw out or in is there a set prosedure on how to go about it cheers :)

Title: Re: carby headache
Post by: lms6201 on August 23, 2009, 06:51:05 pm

does it have an idle speed adjustment screw ?  raises or lowers the throttle valve (slide) not the low speed mixture screw , i had a kx 420 about the same year ,no idle setting , so when hand comes off , shuts fully 

Title: Re: carby headache
Post by: oldyzman on August 23, 2009, 07:34:17 pm

Hey Z man,
 Try the AIR JET, I have just had major issues trying to tune a YZ250, in the bell (inlet) of the carby there should be a jet fitted right in line with the needle which regulates how much air goes to the needle jet. this should maybe be a 2.0mm. After all of my try's to tune i discovered this was not present once i put one in the thing ripped on std jetting. All this is considering that you have a mikuni round slide carby.
OLDYZMAN

Title: Re: carby headache
Post by: zman on August 23, 2009, 07:42:52 pm

no its the standard flat slide carb and the air scew is towards the back with no other ajustment on it

Title: Re: carby headache
Post by: paco on August 24, 2009, 05:56:43 am

Try to adjust the idle by using the cable adjuster.Good luck..everything should idle.

Title: Re: carby headache
Post by: All Things 414 on August 24, 2009, 09:43:05 am

Quote from: paco on August 24, 2009, 05:56:43 am

Try to adjust the idle by using the cable adjuster.Good luck..everything should idle.

I think this option is taking the road best travelled by pain...... :(. You really should have some play in your cable or it's probably going to rev up with the bars turned one way and your choke systems not going to working properly either (with the slide open a fraction).
If your pilot jet is right and the air mixture correct (assuming all else is right and proper) you should be able to get it to idle to some degree (mine usually cut out if I haven't blipped the throttle after 20 seconds or so.)
I usually only use the idle speed adjustment screw to help when I'm playing with the air screw. Once I think I've got it about right I back the idle screw (slide adjustment) right off.  

Title: Re: carby headache
Post by: paco on August 24, 2009, 01:25:18 pm

quite right.

Title: Re: carby headache
Post by: zman on August 24, 2009, 08:38:42 pm

well i played with the air screw today and turned it out 2 turns no idle then 3 still wouldnt idle. so i checked if there was any movement  in the crank and theres about 2 maybe 3mm play in it so can ya get away with that much or not