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 Post subject: Carb Adjustment
PostPosted: Sat Jan 22, 2011 9:23 pm 
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Joined: Sun Jan 09, 2011 4:59 am
Posts: 36
Location: Victorville, California, USA
model: 750 Paso
year: 1986
Hey guys I need your help. I have rebuilt the carb and it now starts and runs but off idle is it flat. but seems ok at the upper end.
My questions is when I disassymbled the card I counted turns on the Idle Mixture screws and the air by pass.
I had 5 turns out on the idle Mixture and about a half a turn on the air bypass.
Can anyone give me an idea of what they should be?

Thanks, Jeff


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 Post subject: Re: Carb Adjustment
PostPosted: Sat Jan 22, 2011 9:29 pm 
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paso grand pooh-bah
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Joined: Sun Aug 01, 2004 12:00 am
Posts: 1097
Location: siena, italy
model: 750 Paso
year: 1988
Manual says to close one of the air bypass and open the other to have a correct balance. in the 750paso FAQ topicthere's a post of mine with the complete carb balancing suggestions :thumbup:

Have a nice job, and

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ex...Red "smooth" 753349 :-(


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 Post subject: Re: Carb Adjustment
PostPosted: Sat Jan 22, 2011 11:15 pm 
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paso grand pooh-bah
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Joined: Tue Jul 29, 2008 9:50 pm
Posts: 3259
Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
mixture screws if the jetting is proper and there are no blockages in the carb should be 1 to 1.5 turns,air bleeds one closed the other about .5 turns out, assuming you have them balanced as per the previous post

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If it ain't broke keep fixin it till it is
88 750
90 906
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 Post subject: Re: Carb Adjustment
PostPosted: Sun Jan 23, 2011 1:22 am 
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Joined: Sun Jan 09, 2011 4:59 am
Posts: 36
Location: Victorville, California, USA
model: 750 Paso
year: 1986
Thank you that helps a lot.
I am confused as this is just a 2 throat weber with one butterfly shaft opening both throats. I dont understand the balance part?


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 Post subject: Re: Carb Adjustment
PostPosted: Sun Jan 23, 2011 3:21 am 
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paso grand pooh-bah
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Joined: Tue Jul 29, 2008 9:50 pm
Posts: 3259
Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
The air bleeds allow you to compensate for minute differences in the flow of air in each throat of the weber caused by very small differences in tolerences between the two throttle plates and chokes. You need a u-tube manometer to measure the difference in air flow between the two,which is why you only need to adjust one of the bypass air screws to compensate. when you measure this difference with the manometer you will see that one side(could be either of the two) will flow less than the other so you will need to allow more air to flow into the other sides bypass circuit to equalize the two to the same level of flow....balanced air flow for both sides of the carb
Hey just to add confusion to all this :lol: :lol: :lol: Adjusting your cam timing between cylinders is in fact accomplishing the exact same thing, balancing airflow into each cylinder

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Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie


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 Post subject: Re: Carb Adjustment
PostPosted: Sun Jan 23, 2011 4:31 am 
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Joined: Sun Jan 09, 2011 4:59 am
Posts: 36
Location: Victorville, California, USA
model: 750 Paso
year: 1986
Ok, got it!....sorta! so the it is measured on the vacuum port on each throat?


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 Post subject: Re: Carb Adjustment
PostPosted: Sun Jan 23, 2011 7:06 am 
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paso grand pooh-bah
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Joined: Sun Aug 01, 2004 12:00 am
Posts: 1097
Location: siena, italy
model: 750 Paso
year: 1988
under the throats, on the maifolds, plugged with a 5mm screw

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Black "DUKE" 751582
ex...Red "smooth" 753349 :-(


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 Post subject: Re: Carb Adjustment
PostPosted: Tue Jan 25, 2011 9:07 pm 
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Joined: Sun Jan 09, 2011 4:59 am
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Location: Victorville, California, USA
model: 750 Paso
year: 1986
Can I use 2 vacuum gauges to balance the air bleed on the carb?


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 Post subject: Re: Carb Adjustment
PostPosted: Tue Jan 25, 2011 9:18 pm 
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paso grand pooh-bah
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Joined: Tue Jul 29, 2008 9:50 pm
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Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
Yeah you could,a utube manometer is simple to make and much easier to use. All you need is about 6 or 8 feet of tubing, something to mount it on and the adapters to tap into the manifolds

_________________
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie


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 Post subject: Re: Carb Adjustment
PostPosted: Wed Jan 26, 2011 7:24 am 
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paso grand pooh-bah
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Joined: Sun Aug 01, 2004 12:00 am
Posts: 1097
Location: siena, italy
model: 750 Paso
year: 1988
have a look at my gallery to see how I made it

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have a nice ride, Nicola

Black "DUKE" 751582
ex...Red "smooth" 753349 :-(


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 Post subject: Re: Carb Adjustment
PostPosted: Wed Jan 26, 2011 8:47 am 
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Joined: Thu Oct 22, 2009 10:38 am
Posts: 247
Location: Mildura ,Australia
model: 750 Paso
year: 1986
Look on Ebay for 'Synchrometer' :cool: :cool: :cool: .Much easier than messing around with the other stuff,very accurate and will fit webers ,dellorto's as well as many other carbs for $30.00. :thumbup: :thumbup: Jay.


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