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Bench syncing carbs baseline question

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15 May 2021 19:59 #848509 by katit
Need some help with baselining or "where to start". I look at FSM and I look at article on bench syncing from file base.
Carbs I have were WAY out of sync, you can see it on pics. 1 shut, 2 tad open, 3 more open and 4 has like 1/8 gap. Thats how it was. I didn't touch adjustments yet.

See attached images from FSM. I am trying to understand, what is this "gap" and why it is there? I am guessing it's to positively shut slides when decelerating. Then cable bracket pivots slightly on a spring. So, from what I see now - gap I have is WAY to big. Meaning I need to raise slides so pulley moves up closer to this bracket. Right now idle adjustor does not even touch pulley.

Basically I do understand how to sync all of the slides, but I need to understand how to set one of them correctly to begin with..

Or, should I go with document in archives and use thicker rod with no idle screw in place? FSM calls for think 0.5-1mm wire


 

78 KZ650B2A - resto in progress
www.kzrider.com/forum/11-projects/615161...s-1978-kz650-project
Other bikes: 1978 BMW R100/7, 1978 Moto Guzzi T3, 2016 DRZ400s

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15 May 2021 20:28 #848512 by Mikaw
Replied by Mikaw on topic Bench syncing carbs baseline question
The gap needs to be where you have drawn lines. It sets the throttle linkage in the correct range so you can have low idle and also WOT.

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
The following user(s) said Thank You: katit

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15 May 2021 20:36 #848513 by katit
Replied by katit on topic Bench syncing carbs baseline question

The gap needs to be where you have drawn lines. It sets the throttle linkage in the correct range so you can have low idle and also WOT.
Ok, I got it I think. I synced all slides, then I lowered all of them to make this gap within specs. Seems like this is it.

What about open throttle limiting screw? Any advice on setting that one? With all way in - slides still completely open. I understand needle still can move up, so how much should it be open?

78 KZ650B2A - resto in progress
www.kzrider.com/forum/11-projects/615161...s-1978-kz650-project
Other bikes: 1978 BMW R100/7, 1978 Moto Guzzi T3, 2016 DRZ400s

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15 May 2021 21:36 - 15 May 2021 21:37 #848514 by Mikaw
Replied by Mikaw on topic Bench syncing carbs baseline question
Nope. Set the gap first with the idle adjustment screw. Then adjust the slides to the spec. .07mm maybe?

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
Last edit: 15 May 2021 21:37 by Mikaw.

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15 May 2021 22:15 #848515 by katit
Replied by katit on topic Bench syncing carbs baseline question
I am confused. What 0.07mm? Nothing like this in FSM

and nothing about using idle adjustment screw. It should be loose not touching pulley. I think I got it rights. Gap about 1.6mm with closed slides

78 KZ650B2A - resto in progress
www.kzrider.com/forum/11-projects/615161...s-1978-kz650-project
Other bikes: 1978 BMW R100/7, 1978 Moto Guzzi T3, 2016 DRZ400s

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16 May 2021 04:54 #848521 by Nessism
Replied by Nessism on topic Bench syncing carbs baseline question
0.7mm is the slide gap for the VM26's.  I'm not sure about the gap for smaller carbs but it doesn't really matter.  It's just a starting point for literally the bikes after the first start so it will idle and not immediately die.

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16 May 2021 07:01 #848526 by katit
Replied by katit on topic Bench syncing carbs baseline question

0.7mm is the slide gap for the VM26's.  I'm not sure about the gap for smaller carbs but it doesn't really matter.  It's just a starting point for literally the bikes after the first start so it will idle and not immediately die.
got it! This one done using idle adjustment screw, not a big deal

78 KZ650B2A - resto in progress
www.kzrider.com/forum/11-projects/615161...s-1978-kz650-project
Other bikes: 1978 BMW R100/7, 1978 Moto Guzzi T3, 2016 DRZ400s

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  • SWest
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  • 10 22 2014
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16 May 2021 08:39 #848529 by SWest
Replied by SWest on topic Bench syncing carbs baseline question
Many carb racks have a "lead carb". Mine is #3 so I set it using irrigation wire then make the rest the same using the adjusters on the other carbs. Jeff @ Z1E says he just bench syncs his  and doesn't use vacuum gauges on his 1000's. I've been doing the same on mine since mine broke. I have to keep the  idle up a little more than normal but it's fine. On the smaller fours you need the gauges or you'll have rattling noise from the primary chain the 1000's don't have at idle. 
Steve
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16 May 2021 08:46 #848531 by katit
Replied by katit on topic Bench syncing carbs baseline question

Many carb racks have a "lead carb". Mine is #3 so I set it using irrigation wire then make the rest the same using the adjusters on the other carbs. Jeff @ Z1E says he just bench syncs his  and doesn't use vacuum gauges on his 1000's. I've been doing the same on mine since mine broke. I have to keep the  idle up a little more than normal but it's fine. On the smaller fours you need the gauges or you'll have rattling noise from the primary chain the 1000's don't have at idle. 
Steve
Thank you! That was my next question (s)

 I just ordered adapters with clear tube for level checking

1. what is the easiest way to bench mount carbs for checking?

2.,what tool do you recommend for adjusting fuel screws on a bottom? When on a bike? I set them to 1 1/8 out per instructions but I understand adjustment will be needed

3. any specific vacuum gauges recommended? There is plenty of cheap ones on Amazon. Will they do or $60-$90 units will be much better?

78 KZ650B2A - resto in progress
www.kzrider.com/forum/11-projects/615161...s-1978-kz650-project
Other bikes: 1978 BMW R100/7, 1978 Moto Guzzi T3, 2016 DRZ400s

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  • SWest
  • Offline
  • Sustaining Member
  • 10 22 2014
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16 May 2021 09:28 #848532 by SWest
Replied by SWest on topic Bench syncing carbs baseline question
I've got my eye on the Morgan carb tune. A little over $100. You set the fuel screws at best idle then I raise the RPM's to 3500 and dial out the misfire if any. Stock you shouldn't have to do that if the float levels are right. I have a thread on my 33's but the procedure is the same. 
Steve

kzrider.com/forum/13-bike-related/597654...aw?start=1104#848484

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16 May 2021 09:37 #848533 by Mikaw
Replied by Mikaw on topic Bench syncing carbs baseline question
Swest beat me to it. I forgot to mention or ask if you rack has a slide that is fixed, no adjustment. If so then you need to select that carb. Use the gage wire .07mm maybe. And adjust the idle screw till the gage wire is a light friction fit to the fixed slide. See picture below that I marked up. Just continue to read from the green highlighted area. On the next page were I placed the green arrow illustrates how to use the gage wire, and it will tell you what size to use. I agree with Nessism, the size of the gage wire isn’t critical as long as you don’t use one that is massively larger. It’s more important that the slides are set to the same height. 

 

here is the stand I made to hold the carb rack for setting float levels and bench sync. An old mower tank is great for auxiliary while setting floats.

 

I use Morgan Carbtune 
www.carbtune.com/

If your buying a dial gauge set get ones that are adjustable. Ive seen the cheaper set on evilbay and scamazon at rest have needles pointing all different directions. 

I think Motion Pro sells a 90deg idle adjustment screwdriver. 

 

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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16 May 2021 09:57 #848534 by Nessism
Replied by Nessism on topic Bench syncing carbs baseline question
The standard type VM carbs don't have a "master carb" or anything to that effect.  I'm not sure about the smoothbore VM's though.  Anyway, if you have a slide that is too low, and cranking the adjuster won't lift it and causes the other slides to move, that means the slide you are trying to lift has an adjuster that is topped out.  I just went through this on a set of VM26's and it stumped me for a few minutes before realizing what what going on.  

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