Author Topic: Bench sync carbs, does this look ok?  (Read 1932 times)

Offline SteveW

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Bench sync carbs, does this look ok?
« on: June 27, 2018, 04:24:35 PM »
My 550 K0 with 022A carbs has been running perfectly except for number 2 overflowing.

I have stripped the carbs today, with new o-rings from Gerben.

Just done the bench sync with a 3.2mm drill bit, throttle stop screw all the way out.  Adjusted for the same gap on all 4 carbs, repeated several times, all bang on the same now.

Noticed that there are more threads showing on the adjuster for carb 1 than the other 3, does this matter?

Haven't refitted the carbs yet, wanted to know if it was ok first.

First pic is 1 and 2, second 3 and 4.

« Last Edit: June 27, 2018, 04:35:14 PM by SteveW »
1974 CB550 K0
1980 CB650
2000 CBR929RR Fireblade
1966 Lambretta LI150 Series 3
1981 RD350LC
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Re: Bench sync carbs, does this look ok?
« Reply #1 on: June 27, 2018, 06:35:40 PM »
I don't think that'll work,  Bryanj has written a really good procedure for this so hope he'll correct me if I'm wrong.

Set the fixed/reference ( number 2?) carb by using the tickover adjust screw to accept the drill bit you are using as a gauge. Then don't adjust the slide on that carb.

Next, set the other three slides to match the reference slide using the same drill as gauge.  Finally, lower the whole set back down to running level with the tickover adjust.

Offline SteveW

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Re: Bench sync carbs, does this look ok?
« Reply #2 on: June 27, 2018, 06:44:41 PM »
Is there a fixed / reference one, there is an adjuster for each carb?
1974 CB550 K0
1980 CB650
2000 CBR929RR Fireblade
1966 Lambretta LI150 Series 3
1981 RD350LC
1972 Raleigh Chopper
1974 Raleigh Tomahawk
2011 Henry Hoover

Offline Nurse Julie

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Re: Bench sync carbs, does this look ok?
« Reply #3 on: June 27, 2018, 06:54:20 PM »
Bryan also suggests suggests using a drill shank that is less than 1mm. I use Bryans method whenever I bench sync carbs and, touch wood, so far have never had a set of carbs that haven't started the bike first time without making further adjustments.
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Offline SteveW

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Re: Bench sync carbs, does this look ok?
« Reply #4 on: June 27, 2018, 06:58:35 PM »
1mm ? I dont think my slides will go down that far  :-\

Really confused now  :o
1974 CB550 K0
1980 CB650
2000 CBR929RR Fireblade
1966 Lambretta LI150 Series 3
1981 RD350LC
1972 Raleigh Chopper
1974 Raleigh Tomahawk
2011 Henry Hoover

Offline Nurse Julie

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Re: Bench sync carbs, does this look ok?
« Reply #5 on: June 27, 2018, 07:04:40 PM »
They will if you release the tickover adjust screw.
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Offline kevski

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Re: Bench sync carbs, does this look ok?
« Reply #6 on: June 27, 2018, 07:06:54 PM »
They should go down that far.

Offline SteveW

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Re: Bench sync carbs, does this look ok?
« Reply #7 on: June 27, 2018, 07:16:27 PM »
Tickover screw was right out.

Going out to garage now to have another look.
1974 CB550 K0
1980 CB650
2000 CBR929RR Fireblade
1966 Lambretta LI150 Series 3
1981 RD350LC
1972 Raleigh Chopper
1974 Raleigh Tomahawk
2011 Henry Hoover

Offline SteveW

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Re: Bench sync carbs, does this look ok?
« Reply #8 on: June 27, 2018, 07:31:22 PM »
Sorry if this is a stupid question, drill bit in air box side or engine side?
1974 CB550 K0
1980 CB650
2000 CBR929RR Fireblade
1966 Lambretta LI150 Series 3
1981 RD350LC
1972 Raleigh Chopper
1974 Raleigh Tomahawk
2011 Henry Hoover

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Re: Bench sync carbs, does this look ok?
« Reply #9 on: June 27, 2018, 07:32:39 PM »
The side with the half moon shape at the bottom of the slide.
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Re: Bench sync carbs, does this look ok?
« Reply #10 on: June 27, 2018, 07:48:21 PM »
Is there a fixed / reference one, there is an adjuster for each carb?

It's usually number 2 carb on many setups.

If you use the adjuster on that carb it moves the whole set of slides (in effect) relative to the whole throttle mechanism,  twistgrip, cable actuating quadrant etc.  You, as loose the ability for the system to fully close itself when released as you take the slides out of range of tgeycable setup.

If you put the reference back to where it was by looking at the fading mark on the screwdriver adjuster,  then match the others to that as described above it should get you back where you need to be.


Offline SteveW

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Re: Bench sync carbs, does this look ok?
« Reply #11 on: June 27, 2018, 07:50:00 PM »
Just tried again, idle screw all the way out.

All 4 adjusters all the way in, the slides are down but I can get a 3mm drill in.
1974 CB550 K0
1980 CB650
2000 CBR929RR Fireblade
1966 Lambretta LI150 Series 3
1981 RD350LC
1972 Raleigh Chopper
1974 Raleigh Tomahawk
2011 Henry Hoover

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Re: Bench sync carbs, does this look ok?
« Reply #12 on: June 27, 2018, 08:19:43 PM »
Something defo not quite right there, the slides should be all the way down, bottoming out. Can you post a picture?. Just out of interest, you are screwing the idle screw all the way out, not in?
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Re: Bench sync carbs, does this look ok?
« Reply #13 on: June 27, 2018, 08:59:48 PM »
The method used here and first described in original post has just moved the adjustment that should've been on the tickover screw to incorporate it into the slide adjusters.
It's because you've started by backing out the tickover adjuster,  then raised the slides by adjusting each one of them to give that 3mm gap.  It's just transfered from one screw thread to the four individual one's.
It seems a benign point but it's the wrong way round and will give you an error you can't later adjust out correctly.

You need to drop the slides back down to where they were,  lift the whole lot on the tickover screw to get the drill bit in and then sync from there.
It doesn't really matter the drill size as long as you can get it in there by raising the slides on the tickover screw to accomplish it.

Offline SteveW

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Re: Bench sync carbs, does this look ok?
« Reply #14 on: June 27, 2018, 09:14:24 PM »
The idle screw is all the way out so its not even contacting with the linkage.

This is a pic of the absolute lowest position i can get the slides. Even if i disconnect the linkage the slides wont go down any further.

This is a pic of carb1, (nearest choke lever), the gap is 3mm.

1974 CB550 K0
1980 CB650
2000 CBR929RR Fireblade
1966 Lambretta LI150 Series 3
1981 RD350LC
1972 Raleigh Chopper
1974 Raleigh Tomahawk
2011 Henry Hoover

 

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