idle problems. need HELP!!!

[shinzon1]

the fuel screws are brand new i've checked them repeatedly. all the pilot holes are clear. no tips broken off. all parts and bodies were soaked for 3 days. blown threw all of them everything is clear. the bike has the mac 4 into 2 exhaust. stock air box. all orings have been replaced on the carbs as well as the intake boot rings. the intake boots themselves r still very flexible and seal tightly. i've sprayed carb cleaner around the boots while it was running and no change. so i don't think its a leak. mains are 102.5 which im sure are small, but ive never seen anything that it would affect at idle and while crusing with the throttle just barely open. pilots are 15. not sure on the needle numbers. i'm at work today, but i'll try and pull one real quick and find out. thanks!

[chuck hahn]

That all sounds real good.. except I think the Mains should be at least 110s or 115 and the pilots up to the 17.5s for a 4 into 1 setup. Then i would also set the clips in the center groove. The pilot screws at 1 out and the air screws at 1 1/2. That is the general conscensus as far as i have been to establish from all the teachings and tutorials i have read. If you want the jets i have there yours free..

[shinzon1]

the voltage is right at 12.5 volts when running. my seats do not have the screens. the only set of numbers i can find the needle on the slide is Y64. everyplace i've read says that the 17.5s are 9 times out of 10 too big? and the exhaust is a 4 into 2 not 4 into 1.

[chuck hahn]

I misread that its a MAC 4 into 2..MY BAD.

[rustybronco]

So rather than pulling the carbs and measuring 24mm or 26mm exactly and thinking they're right; the only way to really know what is happening with your fuel level, is by checking it with clear tubing - running from the drain screw hole in the bottom of the carb to the mating surface of the carb body with the float bowl.

This is really the only way to know the fuel level in the carbs and rule float height out as a factor.

idle is all over the place it might idle at 1500 or slowly start falling till it finally cuts out. it just kinda jumps all over the place.

This make me think you are having an issue with fuel levels and or flooding (too rich).

you need to externally see whats going on the the fuel levels when the idle drops.

[shinzon1]

well i think i figured the idle problem out. it would only do it when it was good and hot. i think it was vapor locking. the fuel hose ran up just a little and i think it wasn't getting enough fuel. but i'm still having the other symptoms of it running lean. i just can't figure out why it started running lean. when i first got it u couldn't keep sparkplugs in it. it ran incredibly rich! now i can't get enough fuel to it. i've got the fuel screws out 3 turns and its enough for it run smoothly but wont put any color in the plugs. the insulator is just white. the ground strap is a light gray.

[Coady]

I find it odd that vapor lock would show up at idle only; it's usually the other way around, as you are using a lot less fuel at idle and the bowls have time to fill again.

It sounds to me like someone stuffed with the jetting on these carbs before & didn't get it right. I believe that Y64 needle is from a Keyster aftermarket carb kit; the stock needle should be a 5DL36 for 1979 or 5F21 if earlier. So I'm not sure where the clip on the needle should be set.

But as i stated in an earlier post I reckon you are lean on the needle and compensating with the fuel screws. I would try the needle one clip richer and put the pilot screws at 1 for fuel and 1 1/2 for air and see how it goes. But first try and get some info on that needle and see if there is a stock position for it. I've read mixed reports on tuning carbs with those needles. You may be better off in the long run sourcing stock needles and then everyone on here and you know what they're dealing with. That's if the needles are the problem.... .

[shinzon1]

ok. i think i may know where some of the stock needles are, but would that affect it at idle though? because with them turned one turn out it will barely idle. when u try to rev it will stumble and try to cut out. i can see where the needle would affect that part just not idle? i'll try that, but it may be few days.

[Coady]

ok. i think i may know where some of the stock needles are, but would that affect it at idle though? because with them turned one turn out it will barely idle. when u try to rev it will stumble and try to cut out. i can see where the needle would affect that part just not idle? i'll try that, but it may be few days.

You probably are correct about the needle not directly effecting the idle with closed throttle; but there is a relation between the pilot settings and the needle circuit. You've got your mixture screw out at 3 turns to give extra juice to the lean needle so you don't die when you rev like you mention.

I reckon you could get a nice even idle with fuel screws at say 1 1/4 turn and turning the airscrews in a little if you try. But as you said the bike will die when you rev it.

[GS750]

It does still sound like an air leak or you are very lean. This may be the float level as steve said. But after 30 odd years the buoyancy of the floats can differ from how they left the factory.


This is really the only way to know the fuel level in the carbs and rule float height out as a factor.

EXACTLY right!!! Mine was the same as yours, the "wet level" does not lie and mine were also 4-5mm variance even though I set them on the bench and was extremely careful!

[shinzon1]

i'm definately interested in those 110 mains chuck. i sent u a PM did u get it?

[shinzon1]

ok. so i found the original needles. 3 of them r 5dl36 and one is a 5dl35. what is the 5dl35 out of? also one of the 36s has a slight bend near the point will that hurt anything? the whole thing just looks a little bowed but u can barely see it.