Author Topic: pre-carb syncing - 022A initial setting (Read 4697 times)

c(b)hris · « **on:** June 16, 2011, 04:50:03 PM »

I've been searching and will continue, but what is the method for syncing carbs that have all four sliders adjustable? If you choose one and sync the others to that one, how do you know where to set that first one? A bench sync gets them close, but is 1/8" drill bit the optimum opening size to sync them all to?

I have 022a carbs on a 75 CB550K.

Thanks.

WarwickE36 · « **Reply #1 on:** June 16, 2011, 05:04:40 PM »

Im no expert. I have a 74 550 (so same carbs)... and I do have a vacuum sync tool. I have synced my carbs 2 times. So far what I have found is...its kind of a pain in the ass, especially if you are way out to begin with. If your bike is idling where it should to begin thats good, mine wasnt (ended up being 1 plugged idle jet)...hence the re-syncing. The first time when I finished i patted myself on the back the realized i couldnt back the main idle screw out anymore and my bike was idling at 1,500 DOHHHH. so my word of advice is leave yourself room to lower your idle when youre done. The manual may cover this... as a mechanic by trade I dont use manuals <insert tTm the toolman grunt here> I joke, i just dont own one as I should.

My procedure the 2nd time was this. Ride bike to work. Remove tank install gauges and get my 42" big country fan blowing on the motor... restart motor and idle until it was warmed up. bring RPMs to 1,500 and view the gauges... mine were all right around 20inches of merc (seems high to me, but this is where mine will all even out). you should have a feel for an average between the readings... as you adjust one blip the throttle a bit to take up any slack in your mechanical elements to the carbs. When finished adjusting snug the lock nut and blip the throttle to make sure nothing has changed. As far as a starting point to where to adjust to, my understanding is there isnt one in particular... Different cylinders will pull more air than others due to wear. A stronger compression cylinder in theory should pull more air than a weak cyl. As long as all cylinders are the same your main adjustment will do the rest. As stated above, leave room to adjust back down to a proper idle when finished. Voila youre done...

crazypj · « **Reply #2 on:** June 16, 2011, 05:08:52 PM »

Adjust all slides down, crack throttle and see if all show same amount of light.
Adjust the high one and repeat.
When they look even, knitting needles have a greater deflection than drill bits cos' they is longer

(plus, won't damage slides)

Frostyboy · « **Reply #3 on:** June 16, 2011, 05:10:58 PM »

I copied this from the Carb section in the FAQs listing http://forums.sohc4.net/index.php?topic=5410.0

I need to sync my carbs but have no vaccum meter. How do I bench-sync?
When I rebuild a set of carbs, I always bench sync them before I re-intall them. Basically, I use a 1/8" drill bit as a gage. Here's how you do it: Adjust the idle screw (the main one) until the 1 carb outside of it is open enough to just let the 1/8" drill bit through. Then adjust the _sync_ screws on the other 3 carbs until the drill bit just fits them as well. You'll probably want to close the idle screw before you bolt them back on the bike, 1/8" openeing is pretty big. This isn't a perfect sync, as there are other things that will affect the airflow to a given cylinder, but it will get you pretty close.

+ like WarickE said, leave yourself room on the main idle screw to come down if you have to.

c(b)hris · « **Reply #4 on:** June 16, 2011, 05:13:55 PM »

Ok, thanks for the replies. I did a bench sync but wondered if that was optimal before balancing them. It seems that it is, so I will move forward and continue with my current methods.

TwoTired · « **Reply #5 on:** June 16, 2011, 05:41:40 PM »

When you have all slides adjustable in a bank of carbs on the bench, you back off the big idle knob watching the slides until the first one bottoms completely on the "floor' of the carb. You just found your "master" carb. Now adjust the other slide for the same position/gap that the master carb has. You will have to give the big idle knob a twist or two to get the bike to run. Remember which carb it was when you vacuum sync (usually the highest vacuum reading). Leave that adjuster alone and adjust each of the others in turn until it matches the "master". Yes, the master will change its reading when the engine changes speed. Keep periodically dialing the big idle knob to maintain idle RPM. Eventually, all the carbs will read the same vacuum level as the master, regardless of idle knob or throttle position.

If you adjust all of them like a butterfly flitting from carb to carb, you run the risk of skewing all the slides so that they cannot close and the idle knob will no longer determine minimum RPM.

Cheers,

WarwickE36 · « **Reply #6 on:** June 16, 2011, 05:44:08 PM »

Wish I knew that before, thanks TT

c(b)hris · « **Reply #7 on:** June 16, 2011, 05:46:26 PM »

Quote from: TwoTired on June 16, 2011, 05:41:40 PM

When you have all slides adjustable in a bank of carbs on the bench, you back off the big idle knob watching the slides until the first one bottoms completely on the "floor' of the carb. You just found your "master" carb. Now adjust the other slide for the same position/gap that the master carb has. You will have to give the big idle knob a twist or two to get the bike to run. Remember which carb it was when you vacuum sync (usually the highest vacuum reading). Leave that adjuster alone and adjust each of the others in turn until it matches the "master". Yes, the master will change its reading when the engine changes speed. Keep periodically dialing the big idle knob to maintain idle RPM. Eventually, all the carbs will read the same vacuum level as the master, regardless of idle knob or throttle position.

If you adjust all of them like a butterfly flitting from carb to carb, you run the risk of skewing all the slides so that they cannot close and the idle knob will no longer determine minimum RPM.

Cheers,

Thanks very much. That's exactly what I needed to know.

crazypj · « **Reply #8 on:** June 16, 2011, 06:52:58 PM »

TT is my translator

Duanob · « **Reply #9 on:** June 17, 2011, 09:55:25 AM »

On the related subject I notice when vac syncing carbs that two seem related when changing settings. Example is the 1&2 carb and the 3&4 carb, because they are attached by fuel lines and vacuum lines. When you adjust one carb the one it's attached to changes as well. How do you combat that? That's always been a problem when trying to sync to one carb.

TwoTired · « **Reply #10 on:** June 17, 2011, 10:24:43 AM »

Quote from: Duanob on June 17, 2011, 09:55:25 AM

On the related subject I notice when vac syncing carbs that two seem related when changing settings. Example is the 1&2 carb and the 3&4 carb, because they are attached by fuel lines and vacuum lines.

You don't think it is because they are attached to a common actuator arm?

Quote from: Duanob on June 17, 2011, 09:55:25 AM

When you adjust one carb the one it's attached to changes as well. How do you combat that?

Skill.
By not adding any bias to the adjuster with downward pressure from the tools, and anticipation of where the reading will be after the adjustment is tightened down.

The right tools helps, too. I made one for the lock down nut.

Cheers,

Duanob · « **Reply #11 on:** June 17, 2011, 11:23:45 AM »

Quote from: TwoTired on June 17, 2011, 10:24:43 AM

You don't think it is because they are attached to a common actuator arm?

Possibly. When one carb is adjusted up the other counterpart ajusts itself down. I thought this was vacuum equalizing itself and nothing mechanical.

Practice, practice, practice!

WarwickE36 · « **Reply #12 on:** June 17, 2011, 11:46:59 AM »

+1 for downward pressure on the linkage... Thats what I meant when I said blip the throttle take take out any slack in the mechanical parts to the carb. This will ensure the linkage slack has settled out.

When adjusting I had better luck when i just cracked the lock nut open and then held it in place with an 8mm wrench while adjusting the screw. If you open the locknut a lot you will have more of a chance of messing the setting up when you go to lock it down. Next time I will donate an 8mm wrench to be a sync tool and heat it up with a torch and put 2 bends in it to make it easier... once youve done it youll know what I mean.

TwoTired · « **Reply #13 on:** June 17, 2011, 12:09:13 PM »

Quote from: Duanob on June 17, 2011, 11:23:45 AM

Quote from: TwoTired on June 17, 2011, 10:24:43 AM
You don't think it is because they are attached to a common actuator arm?
Possibly. When one carb is adjusted up the other counterpart ajusts itself down. I thought this was vacuum equalizing itself and nothing mechanical.

Can't really equalize pressure between separate ducting. Here's the tool I made a few eons ago for the early CB550/500 Carbs.

Cheers,

Duanob · « **Reply #14 on:** June 17, 2011, 12:59:10 PM »

Cool. You should patent that!

My neighbor has a welder and I have a bunch of wrenches laying around. Maybe I'll make one. I'm kind of at the end of having to buy all the tools to keep a Honda SOHC4 running.

mothgils · « **Reply #15 on:** August 23, 2011, 06:16:17 PM »

Quote from: TwoTired on June 16, 2011, 05:41:40 PM

When you have all slides adjustable in a bank of carbs on the bench, you back off the big idle knob watching the slides until the first one bottoms completely on the "floor' of the carb. You just found your "master" carb. Now adjust the other slide for the same position/gap that the master carb has. You will have to give the big idle knob a twist or two to get the bike to run. Remember which carb it was when you vacuum sync (usually the highest vacuum reading). Leave that adjuster alone and adjust each of the others in turn until it matches the "master". Yes, the master will change its reading when the engine changes speed. Keep periodically dialing the big idle knob to maintain idle RPM. Eventually, all the carbs will read the same vacuum level as the master, regardless of idle knob or throttle position.

If you adjust all of them like a butterfly flitting from carb to carb, you run the risk of skewing all the slides so that they cannot close and the idle knob will no longer determine minimum RPM.

Cheers,

When the idle adjuster is backed out, should the slides just drop? Mine stay where they are but can be pushed down. Is there something wrong with mine? I am trying to bench sync them now.

TwoTired · « **Reply #16 on:** August 23, 2011, 06:53:53 PM »

Have you installed the throttle return spring?

mothgils · « **Reply #17 on:** August 23, 2011, 07:56:51 PM »

Quote from: TwoTired on August 23, 2011, 06:53:53 PM

Have you installed the throttle return spring?

wow...it's late and I'm tired. Duh! Thanks TT, not even thinking.

I went to bench sync them and the slide on cylinder 1 carb is higher than all the others. If I adjust it down, the adjuster holder on #1 is not at the same level as the adjuster holder on #2. If I were to reattach the dust cover, it would not sit level. is this an issue? If so, what would be causing it?

TwoTired · « **Reply #18 on:** August 23, 2011, 10:07:48 PM »

The only time I encountered that was when the bolt on the main pivot shaft was bent.
But, I confess, I'm not exactly certain what specifically you are referring to...

Sorry.

mothgils · « **Reply #19 on:** August 24, 2011, 03:43:53 AM »

Sorry...here are some pics to help clarify.

Here are the slides before any adjusting. The slide on the right is #1 cyl. The slide to the left is #2 and is roughly the same gap as #3 and #4.

Here are the adjuster holders before adjusting. (disregard the 4 on the carb)

This pic shows the adjuster holders after being adjusted using a .040 drill bit to set the slide opening gap.

Is the mismatched height ok?

TwoTired · « **Reply #20 on:** August 24, 2011, 10:20:48 AM »

Yes, I see. That would bug me, too.

When I encountered that, it was the bolts that attach the lift arm to the pivot shaft under the top cover. Have you removed those?

mothgils · « **Reply #21 on:** August 24, 2011, 10:37:51 AM »

I removed the two bolts inside the cover to get the slide out to to move the clip on the needle and the replaced them.

TwoTired · « **Reply #22 on:** August 24, 2011, 10:48:57 AM »

If the lifter arm was repositioned on the shaft internally, it would show just as you have depicted.
However, if you left out some parts in the ball joint captures, that would do the same.
At the end of the internal arm, the hex head part is supposed to have a small locater part (I don't know what it is called). But, it applies pressure on the ball under it pushing it into proper position. It's a possible explanation/cause for what you are seeing.

I can take a spare set apart for pics if necessary. However, you can see what the deal is by taking two of them apart to see if all the bits are in both lifter arms.

Cheers,

Duanob · « **Reply #23 on:** August 24, 2011, 11:10:29 AM »

My adjusters have never been the same height eventhough the carbs are synced and running good. I think it's just an aesthetic thing that can bug perfectionists to death. I got over it since my bike is running good and smooth. Even if you bench sync the carbs and some how get the adjusters nuts even they will be changed when you vac sync them anyway.

mothgils · « **Reply #24 on:** August 24, 2011, 02:41:05 PM »

I understand that the adjusters will be different heights but my adjuster holders are different heights.

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Author Topic: pre-carb syncing - 022A initial setting (Read 4697 times)