TOPIC:

2021-01-04 KZ1300 carb sync

IIt's not easy being a perfectionist. Got all 3 carbs close, but not perfect and could not adjust to 'spot on'.

Decided to to start from scratch per FSM.

Lightly seat each adjustment, then 1.5 turns out.

And, it ran like shit. AND Carb 3 was running at 40 inches Hg, and no adjustment would bring it down.
And idle at 2k even with idle adjust fully out. FSM mentioned that could happen if not in the ‘correct range’ whatever that is
Crap. Should have left it 'good enough'.

Swapped hose/restrictor with spare one from CarbTune. Same result, no change.

Swapped Carbtune port. No change, 40 inches HG. Did I break something? Did the butterfly go 'over center' and is now stuck?

Walk away, come back 30 minutes later. Somehow it still hadn't fixed itself.

Then, magic! While adjusting #2, #3 started dropping. WooHoo!
Apparently, there’s some interplay between 2 and 3, where if one is grossly out of adjustment, the other won’t respond.
I don’t know and wasn’t going to tempt fate by experimenting.

Ended up with these readings at 4,000 RPM. Since 4k is the 'sweet' spot for riding, decided to balance there
and not worry about idle specs so much...

Now then, if I could only get #1 to raise by 0.5 "Hg, it would be 'purrrfect'. Scew it, I'm done!

Between ColourTune at idle and carb sync, she sounds audibly healthier.



The end.

Your "sticks" are in cm/hg. 40" Hg vacuum would collapse a rail car tanker to the size of a 40 gal. drum!

scotch wrote: Your "sticks" are in cm/hg. 40" Hg vacuum would collapse a rail car tanker to the size of a 40 gal. drum!

And just for clarification, 29.92" Hg is a perfect vacuum. You can't get any higher then that. Just saying.

Kawboy wrote:

scotch wrote: Your "sticks" are in cm/hg. 40" Hg vacuum would collapse a rail car tanker to the size of a 40 gal. drum!

And just for clarification, 29.92" Hg is a perfect vacuum. You can't get any higher then that. Just saying.

LOL, engineering units. My bad. LOL. And to think I used to pull vacuum down to the microns.. Momentary lapse of brain synapses?

So what say the experts about:
1. Syncing at 4k rpm (idle isn't as nice as before)
2. Interdependency between carb 2 and 3?

Honestly, I don't know what I did to get #4 cm/Hg down...

And was it wise to sync at 4k? I'm starting to think 3k might be best.

Called Jack Wagner at Old School Carbs, going to send them his way for the 'magic'.. Cause my CBX carbs came out perfect...

Let me know your thoughts?

Apparently, there’s some interplay between 2 and 3, where if one is grossly out of adjustment, the other won’t respond.
I don’t know and wasn’t going to tempt fate by experimenting.


It's typical for one adjustment to affect the other two. An example would be: Left carb 9"hg - Center 7.5 - right 6.5. I always start with the Highest value and lower that reading (CCW on the adjuster). The other two will, as a rule, rise in vacuum readings. Then adjust the lowest reading (CW on the adjuster) to raise that reading. The other two will change slightly - generally the reading on those two will lower slightly.
Continuing with this example - I will then adjust the middle reading. This may be CW or CCW on this adjuster. (It depends on other variables). This will usually bring all three to within .5" Hg. Then adjust to two lowest (CW on the adjuster) to bring these readings in line with the highest. In doing so the highest and the carb not being adjusted will tend to lower slightly. Then continue to work on the two lowest readings. It sounds like a lot of back and forth.......and it can be. It's purely patience ! As long as it's understood that one adjustment changes the other two, the learning curve is easier. Also: I will suggest that the manuals recommendation of starting with the adjusters "backed off" 1.5 turns can be changed to 1 turn if this basic method is followed. Attempting to achieve the highest readings can lead to over tightening the adjusters which will lead to linkage binding and a challenge to balance at all. There must be some "slack" for freedom of movement within the connecting linages ball joints.
SO....., generally........Increasing the vacuum value on one will lower the readings on the remaining two. And vica versa.

Ended up with these readings at 4,000 RPM. Since 4k is the 'sweet' spot for riding, decided to balance there
and not worry about idle specs so much.

Balance at 1000RPM. At 4000 RPM the transition jet(s) will be in-play and depending on other parameters the sync won't ( can not) be as accurate. Unless the goal is an idle at 4000 RPM for those Rocket Launches

Now is a timely moment to mention something else. I discovered this past summer that I had leaks on all 3 carb holders. The sealing lip immediately around the ports that mate with the cyl. head had dried and shrunk. The rubber on the mating surface has many voids. I removed the 3 holders, sanded the surface clean, smooth and down to bare metal, then installed a gasket on each.
Something to consider. Making 3 gaskets is easily done and will solve what must be a common problem, based on the many eBay photos of these carb holders being sold .
They all show the same problem.