Idle problem

[RUQKENF]

This is my first time posting on the site. I recently bought a 2004 yz125 and I am having a problem getting it to idle. It will not stay running unless I rev it manually and hold a steady rpm. I tried adjusting the idle screw and it has no effect at all on the bike, no matter where the screw is set the idle does not change at all. I checked the air/fuel screw and it is set correctly. Any ideas?
Thanks,
Tony

[noobish]

You sure the engine is okay? My kids two strokes wont idle when the crank goes out, they start, but they wont idle

[triplendo]

Welcome to , If the bike has been setting for a while the carb. and jets probably need a good cleaning. Thats the first thing I'd try, if it still won't idle you may need to replace the crank seals. If the air screw does'nt effect how it runs it usually means that the jets are plugged or your getting air in from somewhere that you should'nt.

[RUQKENF]

Thanks for the replys, I am going to try to clean the carb first. The engine seems ok, I will do a compression test and see what I come up with.
Thanks,
Tony

[dhighlan]

Hey Tony where in Chi town are you from? It could be a few things but first clean it out (the carb) set the float and make sure you have good gas (93) and a nice clean air filter. Start out with the air screw 1/2 turn out while someone has the throttle to keep it from dying, allow it to rev and drop down each quarter turn on the air screw. I bet you will find the highest idle and then go from there. Write down the jets and settings and post here.

[RUQKENF]

I live on the northwest side near Ohare. I havent had a chance to pull the pilot jet out and clean it yet. The Pilot Jet is a Stock 40 and I believe the main jet is a 430, the manual calls for a 410 stock. I went out and got a new air filter today and a couple of new plugs. It has a FMF Factory Fatty and a Titanium2 Silencer. Thanks for the replies.
Tony

[RUQKENF]

Well, I cleaned the carb and it still idles bad. The only way to get it to idle is if I run the idle screw all the way in until it is flush with the lock nut. I also found out that it has Vforce3 reeds in it. What would cause it to need the idle screw all the way in like that? Could it be too rich on the pilot? The needle clip is on the 3rd postion.
Thanks,
Tony

[jambo]

hi m8 when was the last top end rebuild i had same probs on a cr.
i rebuilt the top end just for pease of mind and it idled straight away i ran it in then ajusted to suit. also check the reeds for any splits cracks holes etc.

[RUQKENF]

It will idle, but the screw needs to be all the way in. I am not sure when the last top end rebuild was though, I just bought the bike. It runs great even with the idle problem.
Thanks,
Tony

[dhighlan]

Tony
I missed your other replies, sorry about that, did you set the air screw? It could be the air screw is set too far in as well. It could be the pilot too rich(which I doubt) but I need to know about the air screw. When the top end is getting suspect the idle because suspect and becomes difficult. Really sounds like the air/fuel screw to me.

[RUQKENF]

I have the air screw at 1 3/4 out.
Thanks,
Tony

[yamahayz125]

i had the same prob with my 03 i just had a top end put in it and changed mix oil to castor927 with premium unleaded gas and it worked fine.

[roostertail6]

Welcome, I am also a newbie to this site but not to repairs. What i would do is check all the basics. fresh fuel,air filter,hoses etc. If all is well there then take carb off and take it apart down to jets. Do this in a way you can lay the parts out in the order they came out. Not necessary to remove jets, this can go bad sometimes as the slot for screwdriver is easily messed up because it is brass and very soft. Use carb clean and spray parts off. This part is the most important, use whatever light you find suitable to see thru jets. they MUST be clear. Weather they are clear or not use compressed air and blow them out. Reassemble carb. Chances are if your carb is not overflowing fuel (coming out) or starving when you rev engine you will not have to mess with float height. If you need or want to check float height use the book. It is rare that i need to adjust a float unless replaced. Check the compression of the cylinder at this time too. Generally, 90 psi or lower is bad. The book may say 160psi but that is optimal. Good luck and take your time.

[levioveracker]

if all else fails, check out your clutch and your tranny for some kind of dragging problem.