Topic: Jetting Question - Need a starting point

[KB02]

I'm a little confused on where to start and need a little shove in the right direction.

Basics:
'78 CB750K
Cycle-X 850 kit 
4 into 4 Benji's exhaust 
F1 style, free flowing air filter (like pods, but better) 
Ported head   
Web Cam 363b camshaft 
Stock carbs   

Opening up the exhaust and and intake indicate that that I should go with bigger jets.
Porting the head signals that I may be good with going down a jet size, but, with the bigger cam and larger bore, wouldn't I be better with bigger jets?

Long story short: I've been fighting the carbs on this bike and think I finally found the problem (the nut behind handlebars, so to speak), so I'm trying to look at this from a "fresh start" perspective. The carbs are fully apart. I've got idle jets from 35 to 42 and mains from stock up to 135. Where should I start for jets as I piece these back together?

[PeWe]

Stock carbs?
Hopefully someone with same carbs and similar setup that can give you a start.

After that visit a shop with dyno. Its well worth the money.
They must check AFR at idle and slowly increase throttle all the way up looking how AFR is on all throttle lifts.
It can be too rich at lower, later too lean followed by too rich.
I have had that which make it tricky to jet based on plugs.

The earlier CB750  round carbs:
pilot stock 40, airscrew 1 or less. Needle 4th notch from top, main maybe 125.

Just wot and measure the power is not first prio.

Another Dyno when you have corrected after first. Same shop and dyno.
Running too rich or lean  or both can cause a high cost

Make sure that ignition is properly set and carbs are synchonized. Bad synched carbs can trick you in the lower rpm area. -Don't ask me how I know

Leaking carb boots and bad ignition wires another issues that have caused a high number of jet changes and test rides for me.
The good thing, I can do it while sleeping or with light switched off!

[Don R]

 My motor is similar and PeWe is pretty close to what it seems to want. I'm at 40's, 1 turn, 3rd notch, 130 are a little much, I'm going 120's for the next test ride.
  Mine's an 836 with 4 cable K0 carbs, no number 4-4 pipes with the baffles in today,  Kenny Harmon F cam, mild ported head, stock valves.   60* air today  around 1200 feet corrected density altitude. Pretty good air so it could make use of a lot of fuel.

[PeWe]

The 130 main might cover up for lean needles as I found on my K2. Bike had not much acceleration so I increased main jets, suddenly it woke up very fine but way too rich at higher speeds.
That was with needles at middle notch (3). Increased 1 notch and reduced main jets.

[KB02]

Thanks. In previous attempts to run this machine, I had been at 40 pilots and 130 mains. The plugs read that I'm running rich as hell, yet it acts like it is running lean.
The PD carbs are kind of the odd-ball for these old SOHC's. The needle is non adjustable. I ordered a rebuild kit for the carbs that came with new needles, which were adjustable, but they were a complete different size and even at their leanest setting they are about 1/4" shorter than the stock needle.

I think I'll stay with the 140 pilots and drop to 120 mains. Perhaps shim the needle? I've got some shims somewhere...

[Don R]

 On the Goldwings they use 4mm stainless washers to shim the needles. I'm not sure of the thickness but they seem pretty standardized.
 I was going the wrong way jetting mine, the guys here got me back on track. Like many things, if you get lost go back to stock and work from there. That's what I needed to do. 

[PeWe]

M3 washers fit fine on my Mikuni TMR carbs.
Almost 0.5 mm thick making one washer to 1/2 step.

Distance between 2 notches is almost 1mm.
I measured the washers to get 4 equal, they can differ a little.