Carb Synch Help - 3rd Gen

I've gotten the front two cylinders lined up fairly well, as you can see. The middle two gauges are the rear two cylinders. I can't seem to get them adjusted properly; it seems like I'm adjusting the idle instead of the relative load. What am I doing wrong?

Alos, the idle is higher than I would like and it isn't touching the idle adjustment screw. I've already turned that little screw on the float bowls to the 1 1/2 turns specified in the manual. I'm confused. Suggestions?

 

If you can't get a low (1200 rpm) idle speed there may be an air leak into the system (carb boots, synch adapters or the rubber lines to gauges) or the synch screws are way misadjuisted and holding throttle plates open.

There is some interaction between the different screw adjustments, but you should be able to do better than the meters indicate.

You understand that the 2 matched rears need to be matched up with the 2 balanced fronts as the last step.

I use that same set of gauges and find that best range of adjustment is when needle is pointing to about the 7 to 8 o'clock position, much less than you have going.

I'd suggest going back a couple steps: set idle speed to 1200 with master carb first, then work on getting the two rears to match up.

Be sure to blip the throtttle a few times between re-adjustments to allow the linkages and throttle butterflys to settle into their new positions.

 

"set idle speed to 1200 with master carb first"

Please explain this procedure precisely, as though I were completely clueless, so I can confirm that I haven't missed anything. I think I know what you mean, but I want to be sure.

Also, regarding the meter readings, how do I get the front two to read around 7 o'clock? You know what, just talk me through it from word go, if you don't mind. I'm new to this and I know you know what you are doing (and you are using the same tool as me!)

EDIT: I pulled the carbs because I suspected I'd gone too far afield to recover. Bench synch and I'll try again this evening.

 

Good idea. With a proper bench synch, you'll be closer to the best starting point.

 

Shouldn't he be adjusting the idle while he's synching it using the large black idle knob?

Adjusting the carbs one by one but keeping the idle to spec using the knob?

 

Okay, I redid the bench synch and I figured out what my problem was. The rear two cylinder adjustment screws were so far off that they were restricting the range of motion on the throttle (which is why it was never coming back to the idle adjustment knob position.) I got out my calipers and set the butterfly-to-top-of-carb-boot height to be equal among the four (I think the distance was 1.420" or 1.355" - somewhere in there.) I'm going to run up to the autoparts store and get some longer vacuum hose so I can see the gauges myself rather than have to get someone else to read them to me and I think I may have this sorted out within an hour or two! :biggrin: I'll report back with the results.

 

i don't think your caliper setting method has much validity, but if it works well enuff to get you started, OK.

Bench synch works best when all the throttle plates are lined up evenly with the first progression hole just downstream.

After visual bench synch it's doubtful that screws would need anything more than 1/2 turn ( probably less) for a match on the gauges.

 

I must respectfully disagree. Pictured below are the results straight off the bench:


I almost don't want to mess with it at all...

EDIT: I didn't. After the bike warmed up, the needles came ever closer to unity and I decided to leave well enough alone. I'm glad I did! It is amazing what a proper tune will do for an old bike like this. Wow. Soooo smooth in acceleration; it's a completely different animal now!

 

Heck ya dude thats the readings im going for my last attempt to sync my carbs for my first time i had no readings at all!!!!! Think im just way off or what? Did you figure it out what do I gotta do? MY CARBS ARE BACK IN THO ALREADY I CANT DO A BENCH TEST NOW!!!!

 

Once you've pulled and reinstalled the carbs a few dozen times it becomes less of a hassle.

If your bike is running okay now, but you aren't seeing any gauge readings, there is something wrong with your gauge set-up. Do you have the vacuum adjustment valves in-line to the gauge from the carbs? If you can't settle the needles before beginning, you won't get anywhere.

You'll have to be more clear about what difficulty you're having for me to be of much additional help.

 

Hey!

My bike has no TAC. So to adjust the idle i gotta do it by ear. Then I wanna sync it!!!

I just reinstalled the carb but forgot to do a bench synch!!!

The bike runs but pops and has an unsteady idle and I just want it back in SYNCH.

So here are my questions........

First off how do I adjust the idle BY EAR? (Didi you just set it to what the manual says or did you fine tune it?)

Secondly How do you Synch? WHERE DO I START? (I have my synch guage all hooked up I'm just waiting on you to tell me how to do it?)

O AND I FOUND ALL THE ADJUSTER SCREWS AND YOU AINTJOKING ABOUT THEM BEING A PAIN!!!!! RRRR!!!!!

GLAD YOU GOT YOUR BIKE RUNNING GOOD I CANT WAIT TILL MINE DOES AND I HOPE ITS TODAY!!!!!!:chaingun:

 

You need to study the service manual for the info you need to synch properly.

 

Manual doesnt tell me how to fine tune my pilot screws. It just tells me 2 1/2 turns out. Is that IT? DONE? Also i dont have a RPM guage but u probly read that.

As far as the sync goes, im gonna try it again tomorrow but i didnt have any luck with it (GOING BY THE MANUAL) last time about half a year ago I dont know if you rerember and thats why I gave up. I tried turning sync screws in and out and some did nothing. So here I am again ready to tackle the project again and read the part here in the FORUM about blipping the throttle after each adjustment. I DID NOT DO THAT LAST TIME, THAT MAY BE IT?

I asked the guy above me cause it was his first time just like its mine so maybe he understands why this is difficult and frustrating for me? I forgot to do a bench sync before reistalling my carbs but the bike runs. Can I do a sync from here or do I gotta take the carbs out and go all the way back to the beginning to the Bench Sync?

 

Yes, i'd go back and start with a bench synch and start from there. From that point (if the bike's running OK at idle) you'd only need about 1/2 turn of any synch screw to bring it to all together. Carbs must be adjusted in a prescribed order as service manual notes.

No need for a tach, just have it ticking over at what sounds like a good idle speed. Not too fast, not too slow.

 

Thats what I was fearing. I will try it tho Squirrelman. What about the pilots? The manual says to set them at 2 1/2 turns out. Can I leave em there or do I have to play with them some also?

Starts fine, idles fine, revs fine. Just when riding after 1/4 turn of the throttle she just starts popping and wont go any faster and the more i turn the throttle the more she bogs down and becomes unresponsve!!!

 

Doesn't seem like that's related to any problem with carb synch but to another problem entirely. Are your vaccum slides moving properly ?

Pilot screw setting of 2 1/2 should be fine for idle IF CARBS ARE CLEAN, no need for further refinement until you're sure bike is running right.

Ever consider trading up for a newer bike?? It may be about time, and over here we can just dream about the variety of cool used bikes that we never got available in EU.

 

Are you saying that here in the EU we have more of a variety of cool and used bikes or in the U.S.? Yes I would like something like my buddy has a Bandit with 126 Hp!!! He lifts his front tire off the ground while hes already doing 60PMH its nuts!!! Im always at full thottle trying to keep up

Its just I want to figure out what the problem is with my Sabre because this is what I really like to do and I was having fun working on it till I got stumped and if Im gonna get any money for a newer bike I have to get this one running good so I can sell it anyways.

Bike takes off normal but bogs down after 1/4 throttle just seems like its not getting enough gas doesnt it? When i release tho its fine again. I cleaned out the petcock and have a sight glass fuel filter and it seems to be working right. Even attached a temporary gas bottle with a hose that was wide open and still had the same problem with the cutting out and popping and all when I gave it too much throttle. When I get this carb off this time I should take pictures but I remember making a small video here for the forum that showed all my slides working awhile back. As far as what I understood they were working right. they were all moving!!! I bought a carb rebuild kit and swapped out all the things in the kit with the old parts in the carb. Had the carb ultrasonic cleaned by a local shop (which I think im gonna have em do it again just so I know they did it right)!!! Ive checked for vacuum leaks and found none. I bought new rubber boots for the carbs to slide into to. Ive checked the timing. Ive adjusted the valves. Compression test was fine. New air filters and so on and so on. Im new to this and this problem is just killing me!!!!!

 

UPDATE!!!!!!!!

Major break though i hope.

You kept saying vacuum slides vacuum slides so I hadda look!!!

Ok first off i pulled the plugs. they were chalky white!!! which means not getting enough fuel right?


HERE COMES!!!!

U know the BIG FAT RUBBER air funnels that sit inside the Air chamber that direct the air into the carbs? I took em out cause im getting ready to have the shop do another ultrasonic cleaning and they dont even fit back in there they are too small cause they have shrunk over time. COULD THEY HAVE CAUSED MY PROBLEM????

AND ALSO The shop that ultrasonic cleaned my carb. seem they didnt even put those rubber sleeves back in right that are in there at the top of the slider in the carb. They were all crickled at the top and there is no way they could have been airtight!!!

On top of that I opened all the carb passages that I could get to and THERE IS ALL KINDS OF BROWN GUNK AND DIRT AND CRAP IN THERE!!!!

IM HEADING TO THE BIKE SHOP TOMORRW THEY BETTER ULTRASONIC CLEAN MY CARBS RIGHT THIS TIME OR THEY LOST A CUSTOMER AND A FRIEND!!!!

 

Some pics.

#1. all the sparkplugs looked like this.

#2 these are the boots in the Air chamber i mean when I say I think they arent sealing righ but not sure how much they matter since they come before the carbs?

#3 vaccum slide boot that isnt sealing right. ALL 4 were on there wrong!!! Think the ultrasconic cleaner shrunk all the rubber or the guys put em in sloppy. I kow I put em in right before the ultrasonic cleaning.

#4 see the gunk down in the passage ways the brown stuff????