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Need factory settings on carb BY-5E, plus questions on MA12S

dear forum,

first a short intro:
im a newbie in here and glad having found you same minded micra lovers / race keen / techheads.
my name is claus, im 53 yo, and herding a 1992 micra k10 with ma12s engine for now 15 years.
all unmodified as to performance, style, sound etc, as she offers fair enough for what i need .
a simple=reliable, lightweight=economic, rear hatch=practical, ugly=no theft little underdog.
i love my micra, and just want to keep her safe and raodworthy cause she serves me well.

now to the situation:
some welding, some brake cleaning/bleeding, some grease and paint here, some attention there.
but finally she didnt pass this years mot test (TÜV in germany) for revving too high in idle at 950rpm.
i noted that when i *slightly* pressed down the throttle cable holder, the revving went down to <900 okay.
but when relaesed same revving over 950.

the misheap:
to make the throttle shaft stay in the desired "900 rpm" mode, i rotated the shaft a bit stronger,
but this suddenly lead to a completely varying revving between dying and higher revving/1000rpm.
i think i damaged something mechanical in the throttle shaft between cable holder behind the carb
and the little switch / fuel level glas in front of the carb.

the investigation:
so i disconnected/marked all vacuum tubes, exhaust return tubes, wiring and the carb
no damage is visible though: throttle flap #1 is open 0.3mm, flap #2 is fully closed,
the little switch (i think it signals "flap open or closed" to the ecu) is working okay.
no metal levers are visibly bent or mispositioned.
i have no clue so far if the damage is within the carb or somewhere else.

and finally, my questions to the esteemed expertship:
what could have been damaged when "under"-rotating the throttle shaft ?

has anyone a copy of nissans factory workshop manual for
a. vacuum tubing diagram between carb, actuators, valves in the engine room
b. what is the little on-off switch at the front of the carb really for ?
c. what are the other electric sensors on the carb for ?

d. what is the correct setting of the throttle damper at idle position
(pretensioned in mm, slightly touching or untensioned some mm out)
e. what is the correct setting of the screw between throttle #1 and the link to #2 ?
i havent touched it but just want to check correctness.
f. what would be your recommendation to hunt down the failure
by systematically checking each component in the engine room ?
remove all vacuum tubes, adjust carb and engine alone, engage back one after one ?

the distributor has no vacuum advance control, the carb has both IN and OUT,
which makes it difficult to determine parts and connections at www partsbase org

the situation of micrists here:
also, K10s are a dying and thus more and more exoticly rare species over here.
the states largest nissan dealer has no micro fiche, leave alone paper documents,
not even a trained mechanic savvy on carbs or any replacement parts off the shelf.

is buying 2nd hand an option ?
im not a guy who gives up without knowing the reason or having tried everything feasible.
buying a new 2nd hand carb from scrappers (hoping its set and working okay) without reason
is not an immediate option. im a ships engineer and fiddler by trade, so i need to know.
still, if anyone has a well working BY-5E carb for sale, pls drop me a pm.

all other tips to shoot the trouble item by item are highly welcome.
if this isnt the right section for K10 normalist , pls move it to the right place.

sorry the 1st posting got that long, but it contains necessary infos.
thanks for your time and efforts

claus the newbie

short after typing my long-ish intro, situation and oodles of silly questions,
i stumbled across the nissan workshop manual trevor from can scanned and uploaded.
thanks a bunch for your efforts, trevor and msc admin !

although its an 1986 edition and thus 6 years older than my 1992 K10,
it nicely explains the tasks, the physical principles and the smart components
savvy japanese engineers installed back 30 years - for our todays enjoyment ...

i saved many scans for studying and later hardcopies in the workshop.
they answer a lot of questions i had earlier, as the too high revving at idle speed...
and that makes me quite happy and confident to get thjings fixed.

have a nice weekend.