carb pilot screw adjustment questions 00' M750 & ignition timing questions

[motoxmann]

can someone please review what I've done and tell me what I did right or wrong, and if I should make any changes to anything?

2000 M750
stock carbs freshly cleaned out 1000 miles ago with stock jetting, needles (e-clip) 1 notch richer than stock, near zero noticeable wear on needles and needle jets
port/polished intake runners
K&N air filter, horns removed from airbox, uncut airbox
Arrow carbon fiber high mount slip-on mufflers
valve adjustment to exactly "rebuilt" specs 1000 miles ago

today:
synced carbs:
set idle to 1100. using emissions nipples: initially H-cyl pulled 7.5-7.75 in/hg vacuum and V-cyl pulled 8.5-8.75 in/hg vacuum. now dead even at 8.25 in/hg vacuum still idling at 1100.

pilot screw adjustment:
I initially had both screws set at 3.5 turns out, but it had a very slight miss at idle. I tried the throttle blip method I've read about and got absolutely nowhere, so I tried my own method. I shut down 1 cyl at a time by closing off its pilot screw then unplugging the pickup coil wires from that cyl's ignition module. idle dropped to ~600. working on the active cylinder, I turned the pilot screw in until it started to have a barely noticeable miss, then turned it out until rpms peaked, then furhter out until rpms dropped a hair and started to sound like it was loading up a little and slight rich smell in the exhaust. both cyls gave identical results (again, remember 1 cyl was "deactivated"):
3.0 turns out slight miss
4.5 turns out peak rpm
6.0 turns out slight rich smell and slight sound of loading up.

I then repeated the same process but with both cyls active, starting at 4.5 turns out, idled at 1200 (I did not touch the idle screw, richening it up from previous setting raised the idle 100 rpms). turned one screw in til miss, out til peak rpm, out further til rich smell and slight loading up sound, then back to 4.5 and same process to the other cyl. and both cyls gave identical results again:
3.5 turns out slight miss
~4.75 (was tough to tell, somewhere between 4.5-5.0) turns out peak rpm
6.0 turns out slight rich smell slight loading up sound.

so I set both screws to 4.75 turns out. it seems to be idling 95% perfect at this setting, and I noticed a HUGE improvement in throttle response and smoothness while cruising and mild acceleration in the range of 2k-4k rpms

also remember, I synced the carbs BEFORE adjusting the pilot screws, so the carb sync was done with the screws at 3.5 turns out

advice? opinions? suggestion on altering jetting? I mention jetting because I've read somewhere that if the screws require more than 5 turns out to be ideal that you need a larger pilot jet, and also because I think I've read the stock pilot screw setting is supposed to only be 2.0 or 3.0 turns out? is this correct?

also I should mention blipping the throttle from idle doesnt seem as crisp as I'd imagine it should be. and after doing all the above I tried various screw settings ranging from 2.5-5.5 turns out in 0.5 turn increments and blipping the throttle, and it seemed best in the 4.0-5.0 range but really didnt make all that much difference below 4.0 and above 5.0

[motoxmann]

oh I should also mention I checked the ignition timing before and after syncing the carbs, and it was spot on at factory setting for both cyls.

but also, a question about the ignition timing:
in neutral I played around with rpm while watching the ignition timing, and whether revving slowly or quickly it reached full timing advance at a mere 2750 rpms, and stayed locked at solid full advance at anything over that rpm. this applied equally to both cylinders. is this normal? I've been tuning high performance cars for about a decade now with full efi tuning software in various makes and models (mostly import and turbo applications), and this type of ignition setup does not seem normal by any means to me. obviously my bike has no way to tell throttle position, but it can determine rpm obviously, and I find it extremely awkward that it reaches full advance at 3k rpms or less. between idle and 2750 it does advance from idle timing to peak timing very smoothly and consistently...

thoughts on this??

[koko64]

The stock ignition map is quite crude, you saw right.

I reckon you have been more thorough than most on the carb synch and IMS tuning. I suggest riding it for awhile and considering a minor adjustment each way to allow for a crisp response off a closed throttle. I wouldnt worry about going a little richer than stock IMS settings. 1. because they are often influenced by emissions regs and 2 you are running sport pipes, K&N filter and no snorkles.

If after a good ride with the motor hot you feel the idle isn't up to sctatch you might readjust a little and find the setting slightly different.
I do both cylinders running with vacuum sticks for not only fastest, but strongest idle. I understand that you were listening for that.

You could use the vacuum tool to adjust IMS for best idle, (highest, strongest idle),  then synch. The tool can let you set the max rpm/vacuum for each cylinder. So I get each cylinder running its best then synch because they sometimes want a different mixture. So I often synch, set IMs, resynch, double check IMS!

[motoxmann]

Awesome, thank you!

I suppose one more question to ask is based on my mods, do you think I should change any of the other jetting or adjustments? Midrange and mid-throttle seems pretty good with the needles one notch richer than stock, but that setting and stock setting are the only I've tried, I'll have to attempt another notch richer to see what happens. The needles themselves also seem pretty accurate for the full range of their effectiveness, so I dont think a taper change will do too much like what the aftermarket jet kits offer.

Full throttle and high rpm seems to be slightly lacking though. Do you think stock main jets are too lean for my setup? If so, what main jet would you suggest?

Btw, I rebuilt my motor 1000 miles ago, reused original pistons and rings though. But I did smooth out the sharp edges in the combustion chambers of the heads to eliminate potential hot-spots to prevent pre-det and improve the squish zone a little. I did not remove enough to affect compression ratio though, I'd guess 0.25-0.5cc's of metal removed.
And I mainly run 89 octane. 87 seems a bit aggressive and on rare occasions rough, but no det sounds. 91 runs a hair smoother and weaker but barely noticeable, and 93+ runs a minorly noticeable amount weaker and smoother and less crisp.

[koko64]

Another thing, I often synch for about 3000 rpm upwards and adjust the  IMS to balance below 3000 rpm if the synch won't hold over the rev range. Some carb types require that and some asymmetrical inlet manifolds require that too.
If your synch holds thru the rev range, then excellent.

Idle mixture adjustments may be compensating for out of synch, and synch adjustments may be compensating for different idle a/f mixtures. So going over each a couple, or a few times lets you tune to a fine point, by eliminating those factors.

If the float levels are out then there's another variable. You have probably set them.

[koko64]

A couple up on the main jet is often a standby with your mods, but many get away without it. A jet kit might stilll be worthwhile, but essential if you open the airbox.

[motoxmann]

k cool thanks