hanging idle, no leaks...

It might be helpful to determine whether one particular carb is responsible for causing the momentary "racing" idle following throttle closure.

When the throttle is lightly blipped during running sync, do the gauges remain equal during the momentary "racing" idle following throttle closure? An obvious gauge vacuum difference during the momentary "racing" idle might help toward determining whether one particular carb is responsible for causing the condition.

If the engine is able to "idle" on 3 cylinders when #4 spark plug is removed and laid grounded against the engine head so it can spark (to complete the secondary loop) -- In this test configuration, does the momentary "racing" idle following throttle closure persist? Same test results with only #3 spark plug removed? Only #2 plug removed? Only #1 removed?

This is making me fall in love with my manual slide Mikuni carbs all over again. :lol:

Good Fortune!

I have to perform this and i let you know.
The awesome thing about vacuum leaks is that i unplugged a vacuum caps while engine was running and nothing change. With a hell of a vacuum leak like this the engine was LOSING RPM, instead of go higher. How its possible to explain this?
Anyway, i think the valvevtiming its ok. Can a 228kg bike do power wheelie with a tooth off on the intake cam? Mh..
PATTON, tell me. What about the way to determinate if my slide valves springs are worn?
The slides does not snap return extremly fast. But they are free and does not stick.

At least for a test, perhaps some added initial compression could be achieved by placing a washer or two (or maybe an o'ring) at one end of the springs before fitting the springs.

Good Fortune!

Another test --- If set idle speed adjustment slightly too low (to where the engine dies) --- when the throttle is blipped, does the momentary "racing" idle appear before the engine dies?

Good Fortune!

Patton wrote: Another test --- If set idle speed adjustment slightly too low (to where the engine dies) --- when the throttle is blipped, does the momentary "racing" idle appear before the engine dies?

Good Fortune!

yes.
the idle is not racing, just take too time to drop.
i have another bike , a 550, with cvk carbs and pods: i tried to get a pod off, then rev the engine while holding with my finger the throttle slide valve up, the idle drop is the same. FAST. i can quite tell the sliding valves have no effect about idle dropping when you shut off the gas and the butterfly valves are close. so does not matter if the valves are too low to return, or maybe not)

what i really don't understand is the fact about RICH or LEAN. here it's common idea that a lean pilot circuit will make the idle hanging. some other people think a too RICH pilot circuit will make the idle hang, due to unburned fuel still present when you close the butterflies.
this type of approach seems to have no effect.
if i set the screws all way IN the bike , of course, stall.
if i set the screw 1/2 or 1/ 1/2 or 2 1/2 or more this seems have NO effect .

my bike present sympthoms of running lean pilor circuit, due to hanging idle, but after 2 minutes warm up she start EVERYTIME with just a look on the starter button. and did not stall NEVER, so i think it can't be a too lean pilot circuits. ..

What i think about is this: As the bike warms up, the volumetric efficiency improves so it requires less fuel to get the same amount of power, the idle goes up. If you close the throttle, it runs off that extra fuel, until the vacuum on the carb slowly lessons and the amount of fuel getting drawn in slowly decreases, hence the slow to idle down.

Did you pull the jets when you rebuilt and confirm they are stock?

Stock , oem and sparkling clean. As the rest of the carbs. Transition holes squirts alot of carb cleaner

if i set the screw 1/2 or 1/ 1/2 or 2 1/2 or more this seems have NO effect...

Does this mean that turning the pilot adjustment screws from 1/2 - 2 1/2 produces no change in rpm?

Good Fortune!

Exactly. No change. If i put the screws all the way in stalls. Otherwise no change

Am wondering if the butterflies were sufficiently closed prior to the bench sync.



Good Fortune!