Starting to hate my carbs,Why can't they just work

Ok, I recently rebuilt my carbs and trying to get everything running right. Its on a 77 kz650. I think I have a pretty good understanding of the individual settings of the carbs but just cant seem to find the right combination of carb settings to run properly. Ive gone bigger jets, smaller jets, different needle position, synced, idle air/fuel screws, check float levels.......repeat process a 100 times. Too rich too lean, no power, no idle etc.

Im wondering if anyone can share some carb settings with me and what has been working for them. Again its a fairly stock 77 kz650, with pods and 4-1 exhaust. Stock carbs (tried these mains so far from 97.5-105 and pilots 15 - 20) I am in florida so usually warm weather at sea level if that factors in to it as well. ) Any suggestions on at least a starting point for the right carb setup (ie jets needle position etc. ) would be awesome, or if anyone knows of a similar post that already covers this.

Pods :laugh:

Might be clogged pilot circuit.

Good Fortune!

[Click on image to enlarge view.]

Im leaning towards no clogs in the carbs. Ive been through them so many times....soaked blasted, the works

I just spent a lot of time setting up my carbs with almost the same settup.
I have 77 kz650 with 4-1 pipe, but I have a K&N filter in stock air box.

What I finally wound up with after many trials and errors was: 2 sizes over stock on the main jets, and one on the pilots.

But the main thing that I learned was not to change more than one thing at a time, and to do the following procedures in this order.

1.Valve adjustment
2.timing adjustment with timing light
(these two should not need to be repeated.

3.float level check.
4. bench sync.
5 dynamic sync.

I did not ever change the clip hight, and did not find it very helpful to mess too much with the air/fuel screws. Just set them all the same about 1-1/2 turns out from seated.

From all of my trials and efforts(I did not always only change one thing at a time, and wasted a lot of time chasing my tail) The most effective adjustments were to set the timing correctly with a timing light, and the dynamic sync.

Perhaps carbs aren't the problem.

If not already done, would assure valve clearances are within 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), advancer functioning correctly (might require clean and lube), floatbowl fuel level assured correct (clear tube test method) , and an assured ample clean fuel suppy reaching carbs.

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

mjkawa beat me to the punch on most of this.

Good Fortune!

There's literally billions of variables with jetting for pods. I would guess 110 main jet is not rich enough. Try in the 115-125 range. I don't think 97.5-105 is hardly a significant change. I was told you wanna jump at least 10#(i.e. from 110 to 120)to really see much difference. Those in between sizes are what you want to really dial it in. What was in there to start with? You are on the right track with the repeat 100 times bit! Now you just gotta use some scientific evidence to base your changes such as spark plug reading, drivability, colortune, o2 sensor:woohoo: You gotta break it down by throttle opening- full throttle for mains, about half for the needle, idle to just off idle for the pilot. After all this not very good info,be sure your carbs are clean and good working order, with correct float level. If it runs with the airbox/stock settings you are on the right track. Once you got the stock setup you may not consider pods worth the hassle for the limited performance gain they provide on a stock engine.

Not sure whats stock on this bike, if anyone knows. I do know that when I got it, it had 97.5 mains and 15 pilots. Right now I have the 15 pilots and 102.5 mains. I thought everything else was ok (valves, timing etc) I synced the carbs a few minutes ago because they were way off from each other. When I dialed them all in ~18-20 on the gauges, now it wont idle below 2000-3000 rpms with idle screw all the way out and no choke.

Be sure you got no air/vacuum leaks! All that carb wrenching can put the hurt on your intake boots. One time I rode about 2 miles with my carbs hangin' loose in the boots by just the throttle cables. Yeah, it ran but not very good.

Rustbucket650 wrote:

... Again its a fairly stock 77 kz650, with pods and 4-1 exhaust. Stock carbs (tried these mains so far from 97.5-105 and pilots 15 - 20) ...

I'd guess 115-117 mains & ~17.5 pilots.

Check & lubricate the timing advancer.

Compression check & valve clearance check.

Ignition checks as per the manual.

Rustbucket650 wrote:

Not sure whats stock on this bike, if anyone knows. I do know that when I got it, it had 97.5 mains and 15 pilots. Right now I have the 15 pilots and 102.5 mains. I thought everything else was ok (valves, timing etc) I synced the carbs a few minutes ago because they were way off from each other. When I dialed them all in ~18-20 on the gauges, now it wont idle below 2000-3000 rpms with idle screw all the way out and no choke.

I'm going to say that you can suspect a leaky carb boot. I just encountered the exact same problem with my bike. I bet that you will find two things if I'm on the right track. First, is one of your float bowl vents drawing a significant vacuum. If so you can bet that that carb has a leaky boot. Second, if you pull the carb rack off, do you find one carb completely closed with no gap between the bottom of the slide and the carb throat. This should be the same carb that draws a vacuum through the vent, and also the same carb that was the lowest vacuum when attached to the gauges. The reason that your idle is raised is because you adjusted that slide so far down that it is pushing the other three up through the linkage. I bet it ran better when you just had it bench synced.

Rustbucket650 wrote:

...synced the carbs a few minutes ago because they were way off from each other. When I dialed them all in ~18-20 on the gauges, now it wont idle below 2000-3000 rpms with idle screw all the way out and no choke.

Perhaps, when bench-synced, failed to first set idle thumb-screw with sufficient threads remaining to further lower throttle slides, which is needed to reduce idle rpm lower than rpm resulting from bench-sync slide positions.

Also, failure of pilot screw adjustment to effect a change in rpm indicates something wrong inside the carb, such as a dirty pilot circuit.

Good Fortune!