lag

got my 73 Z1 running pretty good but I'm still having a lag when I first open the throttle, after that no problem, she's still got the power. Idles good. Carbs freshly rebuilt and bench sync'd (manometer was POS but thats another thread). Adjusted pilot air screws but still a little lag, no intake or exhaust leaks, timing dead on, float levels adjusted, jet needle on slot number 4. running pods on VM 28's, 4 into 1 header I'm at a loss, Suggestions ???

Before anymore adjustments, I'd want to insure the hang up is not in the sync not being optimally adjusted....

Plug conditions?

Possibly a cable snag but hmmm....

If above good, first thought is the needle clip positions... Can always try a different position....

When riding & holding at steady rpm, say 4500rpm, does it feel like it's surging back & forth a little as if running out of gas?

Same rpm, let go of the throttle and let is snap back into position, pop out the exhaust?

Change to richer clip position & or needle...

BTW... Carb Zipped has all your asking for including OEM VM Tuning manual....

kzrider.com/index.php?option=com_docman&...d&gid=461&Itemid=108

thanx it could be a couple of those, I have most of this info already, i DO have a strand broke in my throttle cable but dammit that wasnt it, here's a possible clue, I brought my air screws in to just one turn out to get rid of carb farting. I did try backing them out to alleviate lag but no help. I hit 5000 RPM and a little higher runnin strong (god i love it woulda went faster but i saw a cop) no pop when I let off exhaust, the next richer jet needle slot is # 5 all the way so ... thanx man you gave me food for thought, I had considered jet needle position but ...

If you din clip position 5 works out better then time for a needle size change for you're on the border line... With the new needle, you want to be in #3/4 for optimum performance/AFR throughout your rpm range...

Good luck and let us know how it turns out for you...

OMR

A few other thoughts for you.

1) check the valve clearances. If they are off significantly, the bike can run very rough.

2) check ignition timing - esp. the 1/4 & 2/3 are set the same.

3) check carb syncronization - one carb opening ahead of all the others will give a hesitant response.

4) similar to 1) check compression - if you are down on compression on 1 or 2 cylinders the throttle can be sluggish.

Jet needle clip position #1 at top is leanest and #5 at bottom is richest.

Info from Z1E:

28mm (VM28SC) Z1 & early Z1-A
Jet Needle #3 clip position
Pilot Jet 20.0
Air Screw setting 1 1/2 turns out

28mm (VM28SC) Late Z1-A & all Z1-B
Jet Needle #2 clip position
Pilot Jet 17.5
Air Screw setting 1 1/4 turns out


Would return the jet needle clip to stock position, and retain stock pilot jet size, and return air screw setting to default position. Then proceed from there if finer carb tuning is deemed necessary.

Z1 performed very well off the showroom floor.
Pulling away from idle was strong and steady, absent hesitation or stumble.

Good Fortune!

If not already done, would also assure advancer is functioning properly.

Should see advancer quickly move back and forth as engine rpm is varied by blipping the throttle.

If the advancer is hanging or sticking, it could adversely affect smooth steady pull away from idle.

Advancer may need lube, or both cleaning and lube.

Sometimes an advancer spring may be damaged or weakened.

Good Fortune!

Patton wrote:

If not already done, would also assure advancer is functioning properly.

Should see advancer quickly move back and forth as engine rpm is varied by blipping the throttle.

If the advancer is hanging or sticking, it could adversely affect smooth steady pull away from idle.

Advancer may need lube, or both cleaning and lube.

Sometimes an advancer spring may be damaged or weakened.

Good Fortune!

thats the one thing I havent done, valves done, timing done, bench sync'd a .025 on sliders, carbs rebiult, 20 on pilot jets, 117.5 on (not that that matters) thats gotta be it ...
thanx

Put the needle on #3 clip position and retest.

thats next on my list

went for a ride last night, bike ran fine except ... only lags/hesitates off a dead stop, and is more noticeable if I pull out of my driveway going in the uphill direction. Otherwise it runs good. With my past crab fart problems I'm reluctant to move the jet needle clip higher. It is on 4 right now and going to 3 means leaner correct?? I'm afraid it will go back to carb farting again ....opinions ????

stonemaster wrote:

went for a ride last night, bike ran fine except ... only lags/hesitates off a dead stop, and is more noticeable if I pull out of my driveway going in the uphill direction. Otherwise it runs good. With my past crab fart problems I'm reluctant to move the jet needle clip higher. It is on 4 right now and going to 3 means leaner correct?? I'm afraid it will go back to carb farting again ....opinions ????

Have you done the clear tube test to check fuel levels in your float bowels yet? Accelerating from a dead stop or driving uphill will cause the the fuel to slosh back. Improper float levels might cause the the needle valve to close early due to sloshing effect, thus creating a temporary lean condition. Just a thought.