Syncing issues, need advice.

I posted this in my project thread but don't know if all you knowledgeable guys check over in them parts so I am copying it here..


Got to break out my toy.. $10 of stuff from Ace, I went all out and put a real valve on it.

Used some of that 15w fork oil I have sitting about, nasty stuff that...

Hooked up my home made sync device to #2 and #1. It worked just as planned..

Moved onto #3 and used #2 as a reference.. Started to have issues. #2 seems to be pulling much harder than 3 to the point I can throttle #3 up and hear the engines rpms increase and still #2 has more pull.

I am wondering if this means #3 has float bowl level issues? Or would the problem be with the actual cylinder and should I try and do a compression check? At the moment I a leaning toward float/carb adjustment since #3 was the carb that was in the #4 spot and running dry for a bit.


Any suggestions?

Am perhaps misreading the post, but am thinking should have a separate tube hooked to each vacuum nipple whereby venturi vacuum may be simultaneously monitored on each of the four carbs, because sync adjustment to one carb affects the others.

It is not feasible imo to attempt somehow using one carb as a "baseline" carb and pair-syncing the other carbs to it, because the "baseline" carb changes whenever any sync adjustment is made on another carb.

Good Luck!

I built the rig to spec with the setup mentioned in this thread...

kzrider.com/index.php?option=com_kunena&...96302&catid=3#296302


Hmm, a 4 way manifold... could be done but would cost about $20 more...

Before you start fiddling with your carbs. You cannot accurately adjust all four carbs with that setup. You will need to be able to read all 4 carbs at the same time. What happens is as you adjust one carb it effects the other ones you adjust the carbs until they all read about the same. With your setup you adjust two then remove the tool and adjust the other two. You will be chasing the adjustments all day that way. Make it so you can read all four at the same time.

I tend to agree with that assessment, I might just try to ad 2 tubes to my rig (I can but the parts). I do think the rig will give a basic sync if not a good one. However I am worried I can not make #3 pull more than #2 even when I throttle #2 and #1 down and throttle #3 up.

The bike is running rough but not all that bad. I thought it might just be a sync issue. I guess I could check for a hole in the manifold, but I did the WD40 thing a few days ago and that did not seem to affect the idle, guess I will try that again.

Now that I think of it when I pulled the vac caps of #1 and #2 with the bike running it sputtered as those cylinders went lean, but when I pulled the cap off of #3 the engine raced as if it was starved for air in that cylinder.. Hmmm...I wonder... maybe something wrong with the enrich circuit...

And if not already done, carb sync should be undertaken only after valve clearances assured to specs, brand new sparkplugs with good healthy visibly observed fat blue spark, and ignition timing assured spot-on (especially if using points, gapped and cleaned before setting timing), floatbowl fuel level assured correct, and an assured ample clean fuel suppy reaching carbs.

In other words, carb sync and pilot screw adjustments are the final and very last steps in a complete engine tune-up. Proceeding otherwise is imo a basically futile exercise.

Even perfect carbs can't compensate for deficiences in the other components.

Good Luck!

Patton wrote:

And if not already done, carb sync should be undertaken only after valve clearances assured to specs, brand new sparkplugs with good healthy visibly observed fat blue spark, and ignition timing assured spot-on (especially if using points, gapped and cleaned before setting timing), floatbowl fuel level assured correct, and an assured ample clean fuel suppy reaching carbs.

In other words, carb sync and pilot screw adjustments are the final and very last steps in a complete engine tune-up. Proceeding otherwise is imo a basically futile exercise.

Even perfect carbs can't compensate for deficiences in the other components.

Good Luck!

I agree

I suggest a bench sync first but that means take 'em off and you might not want to but you can get very close.

Advice above is on-the-money. The full sequence is:

1) Valve clearance check/adjust
2) Compression test
3) Ignition (spark & Timing) check adjust
4) Float Service Level Check/Adjust
5) Idle Air/Fuel ratio adjust
6) Carb Synchronization

And yes a Shop Manual is a must.

Best of success.
Bill

mechanical sych first, then synch, then check the mechanical again to asses the damage. Carb synch is more about what not to adjust. The carbs with loos slides will suck in more air with the caps off than ones with tighter slides. The carb that you spoke about was probly near closed. Now you have memory and something to look at when u check the mechanical synch. Record all results in your mind. David Carradean could synch them by psyching them with medation. He wasn't too good with the hoses though. Unless your carbs are new and the slide clearance is equal, mechanical synch is the way to go. Ask george. Where are you George? He's usaully buzy counting giant stacks of green paper. George can tell exactly what the scoop is, he's done more carb work than anyone one this sight and is close to the world record. It doesn't get any better than that. Ting ting, in this corner we have gunnnsonnn! In the other corner the heavyweight title holder and super tuner,, Wiredddddddd.... Geeooorrrgggggge!! And the mikunis are down in the first round! There not moving! One slide on number four carb is stuck wide open! OHHH, that's nasty folks. The crowd is on it's feet as george wraps Gunson's hoses round and round the ropes. There's motion from the opposite corner! The motion pro has leaped onto his back! It's not looking good for George! He spins, grabs ahold of ALL FOUR HOSES AT ONCE! He's ripped them clean out! HE'S DRINKING THE MERCURY!! The crowd is going krazy here! All the carb tool fans are pouring out the door! You can actually here there bikes missing terribly from inside the stadium! George throws his screwdriver high into the air, clamping his visegrip between his teeth, he catches the screwdriver in his ear! He's spreading his arms out wide! SHAKES HIS HEAD UP AND DOWN IN THE MOST VIOLENT FASHION! iT'S been quite an evening at the shop! Wait, he's turning green in the face! Too much mercury?? O my god, he's turning into a futuristic human carb synchronizing ...... CREATURE OF SOME KIND! YESS! this is exactly what I paid for!

Fixed and synced..

Pulled the carbs and adjusted #3 float and did a manually sync as well as reset the air screws.

Used the gadget to sync it and all went well, #2 was a problem, so I did that one last. Now she idles and revs nice, none of that stalling clunks.. Will get it on the road in the AM and I am hoping I am done with my tuning chores.

Also checked the ignition, and as per the prev owners description it is a fairly new solid state unit. Sweet..