help me please with carb adjustment

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millermike
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help me please with carb adjustment

#1 Unread post by millermike »

I just opened up carbs on 1981 xj 650. and both air screws are turned all the way tight. how far out should they be ruffly.

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HYPERR
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Re: help me please with carb adjustment

#2 Unread post by HYPERR »

Hard to say for sure but most bikes I've tinkered with seems to like around 2 turns out. Depends on the elevation too. I would do 2 turns out and then tweak it from there. Do you have access to them after the carb in on the bike? I usually put T-handle screws so I can mess with them afterwards.
2008 Ducati Hypermotard 1100
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1996 Ducati 900SS

millermike
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Re: help me please with carb adjustment

#3 Unread post by millermike »

no there inside carb 2 brass jets, im not sure if im even adjusting right screws there both tightened all the way down.

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Re: help me please with carb adjustment

#4 Unread post by HYPERR »

millermike wrote:no there inside carb 2 brass jets, im not sure if im even adjusting right screws there both tightened all the way down.
Are you talking about the jets or the mixture screw???
2008 Ducati Hypermotard 1100
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2004 Honda CBR600RR
2002 BMW R1150R
1996 Ducati 900SS

millermike
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Re: help me please with carb adjustment

#5 Unread post by millermike »

im trying to adjust mixture screw but im dummy, not really sure were located and cant afford to take it in

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Re: help me please with carb adjustment

#6 Unread post by HYPERR »

millermike wrote:im trying to adjust mixture screw but im dummy, not really sure were located and cant afford to take it in
You have the carbs out and apart?

You have four carbs, yes?

They are Minkuni CVs?
Last edited by HYPERR on Sun Jul 17, 2011 3:53 am, edited 1 time in total.
2008 Ducati Hypermotard 1100
2006 Kawasaki KLX250S
2004 Honda CBR600RR
2002 BMW R1150R
1996 Ducati 900SS

millermike
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Re: help me please with carb adjustment

#7 Unread post by millermike »

no just pulled needle valve out. my bike is running real lean and i need the mixture screw adjusted

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Re: help me please with carb adjustment

#8 Unread post by millermike »

4 carbs its a xj 650

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Re: help me please with carb adjustment

#9 Unread post by HYPERR »

millermike wrote:no just pulled needle valve out. my bike is running real lean and i need the mixture screw adjusted
What do you mean you pulled the needle valve out?

What you are talking about is the pilot screw. Those are usually capped with plastic caps or metal caps that have to be drilled out depending on the year of the bike and the severity of the emission standard of that year. I'm not sure if they even capped them in 1981, if they did, it might just be a plastic cap.

The pilot screw only adjusts the mixture at idle so it won't help much for the lean condition at rpms much above idle. For those you will need to change the jets and adjust or get a new needle.

As for the pilot screw, as a baseline, turn the pilot screw to a position that allows the highest idle. Then adjust the idle screw to get the idle back down to where it's supposed to be.
2008 Ducati Hypermotard 1100
2006 Kawasaki KLX250S
2004 Honda CBR600RR
2002 BMW R1150R
1996 Ducati 900SS

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Re: help me please with carb adjustment

#10 Unread post by HYPERR »

millermike wrote:4 carbs its a xj 650
Yes correct.

Are they mikunis?
2008 Ducati Hypermotard 1100
2006 Kawasaki KLX250S
2004 Honda CBR600RR
2002 BMW R1150R
1996 Ducati 900SS

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