belt snapping issue found ( 99.9% sure ), 2 reasons.

[br4inl3ss]

thanks.
im am very rich. way too rich. my wideband tells it, and can feel it too.
thing i... 5 different carb, even a brand new genuine keihin ( refound, useless ), nothing to be adjusted.
needle, slow jet, main jet, air filter... NOTHING. same happen with all the carbs, just at different point for the main jet.
my stock PoS need a 96 jet ( 94 way too small, 98 way too big ) bit still too rich with the 96. my naraku's need 88 IIRC, 86 way too small and 90 way too big. still too rich with 88.
Glixal PoS carb ( 20mm ), same apply but i dont remember the jet. but 2 point smaller is way too small, and 2 point bigger is way too big.

when i way way too small, it barely accelerate and overheat like cracy ( can hit 350 CHT in less than 5 min WOT starting right after choke disengage ). wideband needle stays jammed in the 20:0.1 position.
when i say too rich, engine flood, hard to start, need to WOT to start it and keep it WOT for 10 sec else it will stall. wideband needle stays jammed in the 10:0.1 posiion. from time to time, it can lean out a bit like 11.5:1 at best.

literally impossible to make any diaphragm carb work. if i had the money id like to try the 450$ keihin carb again now sicne i fixed alot of issue... but no money and unavailable locally anymore. so i bought a dellorto phbg 19 that should work as suggested by all tuners that do 4t around ( one of them do at least 5 of those carb swap on 4t a month ). should receive it next week if it all goes right.
i received the throttle cable bend from Polini.
cant wait to start fitting the carb and see if i have to mod my storage bux under seat for it to clear.

if i still have fueling problem, then its cheap head with invisible leaking valve. i have absolutly NO leak anywhere, verified over 30 time by now.

for cvt... yup most of my problem are fixed, but the belt slipping on variator issue.
received yellow and red Malossi contra spring yesterday. right when i noticed my crank seal elaked AGAIN, the purolator truck showed up. ordered Naraku QUALITY seal kit, hoping the cank wont destroy it....

for the low rpm issue, yup its probably related to running way too rich. but thats not related to the belt sliping on the variator...
and this issue make me pulls my hair.... god i even saw a scooterre bistro 50 ( taotao atm-50 rebadged ) with a 88cc usign stock contra spring and absolutly no slipping anywhere. that thing is a fucking beats. 70cc 2broke scoot stays behind up to 75 km/h ( he accelerate way faster but those bws and keeway 2broke goes way faster, most hitting 110 )

[kosmos]

if your not going over 350 on an air cooled motor, you're doing ok.  and i dont think your rpm's dropping is a belt slip issue. if anything, the motor rpms would increase since there wouldn't be any resistance to it.

[br4inl3ss]

thanks .
no rpm dropping is not slipping... rpm increasing is.
it takeoff to 6.5k ( i think... rpm gauge is slow and so rich it bogs down like no tommorow ), from 15 kmh its climbing to 7.3-8.5 ( depending on spring/roller combinaison ), and then slowly drop to 6500 or so.

ive put my newly received malossi yellow spring and didnt change rollers ( 6g and 6.5g ). still feel the same slippage after takeoff. no wind on flat it reach 7600 rpm. now thats way better. but its still slipping after takeoff.
we can feel it. and if i put a new belt on, we'll see it on the belt. very fast...

rpm does increase... but only at specific rpm range... like from 10% to 30%, if we put mark on the variator like we do on twist throttle to tune the carb.

asked many people and all said it should be a pretty much stable rpm all the way from takeoff to cruise. some setup will increase rpm at WOT to get more speed, but should be stable from takeoff to cruise. exactly how i see all scooters around town, 2 stroke, 4 stroke, new, used, modified, nameit.
my brother yamaha vino is extremly stable too. 7300-7400 from takeoff to cruise, and reach 8500 at WOT. stock engine with malossi multivar 2000 variator and malossi yellow spring. not sure on rollers.

ok 350f is fine. is there a normally calibrated temp gauge on the market anywhere ? they all flash in warning mode at 250... its my 7th gauge now and still warn at 250f ( koso mini 4 temp - rpm - clock - volt ).
ive seen the ugly stage6 speedo cant be set to warn at wanted temp, but half the website says its 250f max once again...

also noticied most crank seal are rated to lower than 300f. what about that ?

[kosmos]

my air cooled 2 stroke ive ran it all the way once, forgot to put the fan back on and my temp gauge i suddenly noticed it was 492.. stopped, and walked it back until it cooled down to around 300.
never had a seal give out. find out what your bike is copied off of and if your seals go out, buy them from that manufacturer. i dont know about cross referencing chinese 4 strokes. but an air cooled, i know a 2 stroke and pretty sure its the same on 4 strokes its just air cooled, 350-380 no more isn't something to be worried about. I mean if it barely touches on 380 then and its the best you can do and you never see over that, then that shouldn't be nothing to worry about. 390 is really getting worrying so is 400. 400's like stop. thats fahrenheit.
a trailtech temp gauge goes to 500F.
but i think air cooled 4 strokes and 2 strokes should be the same for temperatures
Also I kept tuning my bike and recently so ok, i first lowered my main jet as my temperatures were barely getting to 320. then i kept still having this like 4 stroking; this is a 2Stroke, like i was missing some fires on wot, so i messed with needles, leaning them and switching them. finally i thought, must be the pilot jet. lowered it. had to mess around with the needle, leaned the needle with the clip, fijnally changed to the leanest needle. ran fine but with a small cut out down low. so i used the clip and richened it. still there but not as bad. richest setting, it ran and the temps were barely getting to 330's on wot. so i leaned my main jet. now i dont get over 345's, long run, slight up hill on the way back. was teetering back and forth around 345-44. and it runs great. i need to mess with my mixture screw and i think itll be set.
so learn how to set up your jetting. then maybe that will be the cause of your lowering rpms. is the throttle very responsiive in all positions at full throttle? maybe its holding back because its missing firings, with too rich or something. if you have an exhaust temp gauge and its tellin g you rich, try getting your carb set first.

[br4inl3ss]

thanks.

its not responsive at all. only SIOMETIME at 45-50 km/h snapping the throttle i feel it got some power. whatever the rpm is.
else its not responsive.
i know its way too rich, but nothing fix the issue.
needle position, 3 different needle ( unknown type/model/whatever, they're from my 5 different carb ), different pilot jet, different idle setting, different main jet, different draphragm.... i even bought a keihin but returned it. way too pricey for no reason and didnt change anything. 2 Naraku, 2 unbranded, 1 keihin, a glixal.... nothing. but they're diaphragm carb and every shop have nightmare with those. and i start to understand why.

i cannot set the idle properly. its either too rich or too lean, and if i'm lucky to get the idle acceptable mixtur wise, then the rpm is either way too low or way too high, and cannot change it else it change the mixture to way too elan or way too rich. impossible to get an acceptable setting.
the moment i touch the idle speed screw, even barely turning it, the wideband go crazy right in opposite direction and i know the wideband is right because i feel it. its either way too rich, or way too lean. even 1/12 of a turn on the mixture screw completly change mixture AND idle speed alot ( like 500 rpm ). literally impossible to tune.
the only setting i can get is 2200-2500 rpm, way too rich idle, and way too rich all across the throttle position.

no leak to be found anywhere by myself, my brother havign experience with 4 stroke engine sicne over 35 years, and friendly mechanic that doesnt vomit hearing " 4 stroke scooter " ( yup even yamaha ) or " chionese scooter " cannot find any leak.
they found a miscropic leak on valve using leakdown tester, but they've never seen any issue with such a small leak.
heads have been repalced twice, and valve twice too ( on each head ). always lapped.
last time i lapped them i didnt even check for any leak, i was done working for absolutly nothing.
i did test before, because people were stubbord its leaking valve... but it wasnt back then so ofcourse it didnt fix the issue.
i can reproduce the leak myself using my way ( no leakdown tester ). put gas/water/whatever liquid you can find ( different viscosity ) in either intake of exhaust port and see if it leak for about 2h. turn the valve and repeat.
no leak. but if i put liquid on the valve itself, and blow 90 psi of air with a air gun, then i can see very small bubble from time to time.
very minor leak. they all agreed that such small leak shouldnt cause any problem. but maybe they're on coke ?

so... since people are stubbord its vacuum leak ( i even pushed 40 psi of air right in the damn intake with homemade adapter. no damn leaks ). and i cannot get any help locally because of them 4 stroke type ( diaphragm ) carburetor, i ordered a famous dellorto phbg 19 ds. correct size for my 72cc, calculated by 3 carburetor specialist. according to my search they're spot on.

if for whatever reason its still impossible to tune at all again, then the problem is my valve 1000000000000000000%. but at this point, no idea what i'm gonna do... anyway with a dellorto phbg, i can get any part i need everywhere. i dont need to order 5 different chinese crap hoping to get one that is the same as mine. what a damn huge step !!!


thanks for letting me know even 370 is not a problem. i foudn it weird that some people said even 310 is way too hot because i dont get any sign of overheating but my cheap crank seals. no lack of power, no weird noise, nothing.
its weird too that all thet emp gauge i got on ahnd warn at 250f... makes no sense... but they're made this way.
been running Koso for YEARS never had any problem and great product quality ( ofc its not glowshift autometer and so on ). but this one and other i have warn at 250.... really weird. i tought maybe they're calibrated for liquid cooled 2broke engine... i dont know anything about those but the fact they need rebuild very often. but someone said even liquid cooled 2broke hit 300 all day long and they're made to handle that.

[GrumpyUnk]

Maybe your meter is in a place where vortex currents sweep/don't sweep and you get 'pocket' readings.(wideband meter)
The odds of 5 in a row being unable to adjust is .... not very likely.

I have seen the condition where the idle is set a bit too high, tending into the bottom of the transition circuit. Mostly because the actual idle circuit is clogged or has the needle too lean. It won't idle so the hard stop(mechanical throttle position stop) is adjusted to bump up to a more stable idle. The carb then becomes so finicky you cannot breathe on it without it changing how it runs.
As a suggestion, lower the idle stop until the throttle plate is completely closed. If in hand, you can look for light(move slide up). If not in hand, figure a way. Then adjust 1 turn from completely closed. Adjust idle mix 1.5 turns from closed gently. Make sure byvalve is working.
See if it will start and run on the byvalve. If so, keep close as when the byvalve is done, you will be on the idle circuit. IGNORE THE WIDE BAND for a while.
Adjust idle mix & hard stop for ~1500 rpms. See if you can get a good steady idle. If fuel supply to the float bowl is managed, and the supply is good, it should idle w/o problems.
If not. Hmmm. Push it off a cliff.
tom

[br4inl3ss]

thanks.

all you sugegsted have been done by me and 4 different people.

as i said at leas 10 time in the past on this forum ( yup that much problems ), even without the sensor the exact same problem happens. same sound, same feeling, same everything. so even tho i uninstalled the wideband at least 5 time, i put it back trying to see where the heck the problem comes from sicne it doesnt change anythign with or without.

last month i wanted to remove it, but scooter started to run bad and run way hotter. damn it was running at 17.5:1 for no reason. reached 300 F o idle.... i knew by feeling that it was running lean but since i had way too much problems i wanted to be sure. put it back on and i was right. way too lean.

pushing it off a cliff was my first tought.
but i need it and no way ill give 4500$ for a 2006 bws with no registration need inspection and need a new engine. NO WAY.
there is ONE, not two or tree, but O N E chinese scooter with a decent price, its about 3h away and no way to get there and get it home ( need a carb so not working right now ).
thats the reason i keep it. no other choice.

[br4inl3ss]

ok small update.
received this baby


on reddit 3 person told me they went thru many of those weirdo diaphragm carbs before. they said its unlikly but possible.
one with a harley had the dealer repalce it with original keihin 6 time in a row within 3 months.
they never found the problem, but the last one fixed the issue.
next step they were replacing the whole bike under warranty. just like they do with german car with repetitive unfixable electrical issue.

so as i said, now if i still have problems, i know its not the carb. and ill get even more help, they wont vomit hearing " diaphragm carb ". only other cause is valve. i know i have a VERY minor leak, but everyone said it was fine.
and thats the problem right there... 10 knowledgable person, 5 say a version and the other 5 say another version.

in the car world, absolutly no leak should be present. i know, been there done that as a ex PERFORMANCE mechanic ( not electrician with modern car, whats why i quit ). but apparently the small engine world is different. i don't know. its weird, old head was leaking, new head was leaking, repalced valve in the new head was leaking.......... it was worse with the old head but didnt change anything to the fueling issue.

[br4inl3ss]

update:
didnt fix my whole issue but at least now i get some change according to what i do.
if i remove air box, it become too lean WOT on center stand.
downjetting keep it too rich, but i see some change now. i mean i FEEL it ( plugged wideband sensor bung with a bolt made for this purpose so you cant say its my issue )
small screw completly seated still allow too much fuel on stock main jet ( thats should be of the correct size according to all shop working with dellorto ), but now at least i see some change there.
also idle speed scre doesnt change the mixture anymore. it actually only change the speed unlike my other crab.
HUGE GAIN

so that tells me even if it didnt fix all my issues, i def had some carb issues.

now lets find why the heck i have those problem.
vacuum/air leak ? cant find any.
what stuff can i use to check again ? soapy water ? i dont have much inflammable stuff anymore and nearby hw store are waiting delivery trucks.
ill try to fabricate another adapter to push air in from the intake again. i accidentally trashed mine yesterday.

and about valve leak.... should there by any ? some say no not at all even at 90 psi+, some say its not a problem, some said the very minor leak i had were too small to cause any issue.
bu the leak i had on the valve was noticed by putting liquid on combustion chamber and pushing air on intake or exhaust port. thats not alot of pressure... yet some buuble could be seen. so im not sure why some people said its normal, but its what they said.

i ran out of coumpound so ill try something else to lap my valve... ive heard tooth paste could help even tho it could take ages ? else i have headlight restoring stuff that is abrasive but i think its worse than tooth paste.

it MUST be either valve leak or impossible to find vacuum leak. no other way around.


EDIT 
leak fond !

made a proper adapter to put pressure in the engine ( from intake ).
first i sent 20 psi. tought i hear something, but not sure. my adapter was trying to pop out.
reseated it, tightened harder, pushed 40 psi. we can hear the pressure escape somewhere in the head, either by valve or valve seal.
used copper wire to secure my adapter in place so it doesnt pop out, set comrpessor to 50 psi, and the leak could be heard at least 20 meter away, all that with birds and bugs noise.
so i released the air gun so i can stop the constant pressure, and we can hear the pressure escape within 3 second max, no longer ( the gun doesnt release the pressure. valve leak does ).
thats a huge leak !

ill remove the head and chek what is leaking that bad. strange, because the head was brand new, valve been changed for other brand new valve ( new head assy with valve and all had leaking valve ), and seals changed too.
i have a new unopened bag of 2 seals so thats ok. but if its still valve leaking, not sure what my best and fastest option are.

yet everyone was stubborn ( on reddit, other forum, and 2 people here ) i had a intake or vacuum leak... lol.

not sure thats my issue tho ( never seen overfueling issue because of valve / seal leak in car history. ive seen all sort of issue but not such ). we'll see. an engine is an engine, but there is many different factor from small single cylinder engine and big ass V8 modded to death... ran a v8 350 with 48 psi on 6 cylinder and 90 on the 2 other run fine but low power ( it was starting better than a 2023 brand new car ). so yeah what i know about car doesnt perfectly apply to 4 stroke scooter

[GrumpyUnk]

putting liquid on combustion chamber and pushing air on intake or exhaust port. thats not alot of pressure...

This is not a valid test. Period. The pressurized air in the intake or exhaust port will unseat any valve, well, any 'poppet' valve that is held closed by spring pressure.
Valves are not DESIGNED to hold pressure in the above test. They are designed to hold pressure in the combustion chambe, not either port. I expect you will find leaks in just about any valve you test using this method.
I still think your hard stop is not set properly. If you close the idle mixture screw completely, and it runs without opening the throttle at all, then it is running on other than the idle system. It is also possible the float level is too high. Have you backed off the hard stop so the throttle plates are totally closed? It takes VERY LITTLE to get a 39/63/72cc engine to run at idle(see idle jet size - miniscule, size of a wire brush bristle). The idle hard stop screw should be barely turned at all... and if open more, you are at the low end of the pilot jet range... transition circuit and it will NOT want to start reliabley, will not want to IDLE reliably, and will be a mess to drive with the mix all over the place because it is in transition from the time you open the throttle the tiniest bit.
what ever
tom

[br4inl3ss]

thanks Tom.

the valves stopped leaking immediatly after lapping them correctly. no leak anymore at any position. not even with 100 psi on the compressor. keep in mind the port are open and its just air gun not a pressurized system...
there wasnt much pressure, mostly flow. id be surprized it was more than 5 psi inside the port.
valve leaking fixed.

hard stop ? it barely touch the idle speed screw when closed. even with no cable installed. tried different setting there.
even tried to set it so .002 feeler gauge pass with good resistence ( we can see light thru it ) then BARELY turning it clockwise, like 1/8 of a turn or a bit less. then turning it counterclockwise 1/4 and it doesnt touch at all. logic.

the float have been adjusted over and over and over again with no success.
a chinese scooter dealer accepted to give mine a try on its free time ( outside job time ). no good either, but its the same setting he use on the one he sells.
wasted so many time following the float height guide on here before realizing it doesnt make sense at all ( different carb = different mold = different measurement and so on ). with my 5 carb they're all different ( but the 2 naraku, they're identical to each other but different from others ). thats the reason many shop dont want to tune those chinese carburetor. they would need to put way too much time to find the right setting and customer would never pay that much money only for that.
give then a DECENT carb, one that is identical from machine to machine ( like 3 yamaha vino carb, they're the same all across them ), they will do with pleasure.

there was a time i had to screw it in alot. like 4 turn or so. but back then it was starting fine both cold and hot. idle was correcly set with het and screw, but wasnt stable after each start. NO WAY to unscrew it at all.

with those carb, no change happen with or without air box attached. with the phbg, it makes a HUGE difference. so the upgrade was worth considering all other adventage.

we can keep saying i have a leak ( since it bypass the idle circuit, and everyone on other palce are stubborn its a vacuum leak ), but where ? in the rear tire lol. valve not leaking anymore even with more psi on the compressor. rechecked intake manifold too. couldnt find any leak there either. pushed to 40 psi and under water. no bubble at all. valve readjusted for the 458973957397th time, this time to .004/.005 and no change tither. it was .002/.003 last time as someone suggested trying this. no change anywhere.

with cvk carb ( stock, glixal, naraku, keihin ) there was absolutly no change with or without air box. with the phbg i see a huge difference. still too rich at idle with screw fully seated in, and WOT also change alot with and without air box. huge win.

with cvk carb, even 33 pilot jet is way too big. my phbg seems the same ratio of " way too rich " but with 45 pilot jet.

[GrumpyUnk]

The A/C guy was looking at the condenser, giving it the once over. It was not cooling.
He said, "maybe I'll give it a shot of 22."
Customer: "What?!?! Shoot my compressor? That would not help it cool."
Tech: "No, a shot of R-11 refrigerant. It could be a little bit low."

So, either way, give it a shot of 22. 22lr, short or long. It may fix things. It may not. But at least it would settle things one way or another. I jest. But the wife did wonder about 'giving it a shot'...

I have not fiddled with float settings on any of the many carbs I have fiddled with. I have not had the variance you describe. In my fiddling, I cam to the conclusion that they are finicky, touchy, and delicate little flowers... that may sometimes need to meet a large sledghammer. I digress.
The main things I have noted are 1) pilot jet must be open so you can see light 2)main jet clean 3)emulsion tube open thru the middle and all side ports clean 4) needle must be free to move in the main jet/emulsion tube 5) diaphragm must be flexible and intact, and must seal properly so you hear it when you move the slide via the venturi. 6)hard idle stop must be almost fully closed 7)byvalve must work, must seat properly and the needle fit into the jet recess 8) the opening in the float bowl must allow fuel to the chamber the byvalve brass tube slips into. 9) the accelerator pump must work, having a decent diaphragm and the float valve port must allow fuel to flow into the pump area and 10) the throttle linkage must operate the accelerator pump as soon as the throttle starts to move without any lag.11) the idle mixture screw must have the flat washer and the O-ring or it will not work properly and 12) the port into the venturi for the idle mix should be clean such that squirting carb cleaner backwards produces flow out the mixture screw channel and also down the pilot jet more or less.
I started the bike in the garage after having it sit since last fall. I failed to click to RUN with the kill switch the first time... so it took a while for my brain to engage. Flipped to RUN and boom, it started right up. rrr.rrr.VROOM. maybe 3 seconds of crank. And it idled fast. Slowly dropping rpms as the byvalve got heated.
These little boogers want to run. If they do not, there is something wrong.
If you do not need the airbox for it to run properly, I would bet on it being over fueled. Regardless of what a meter says.

tom

[br4inl3ss]

thanks Tom.
tank you alot for your time.

overfueled is exactly what the meter says, anyway.
its also what it feels like.
its what i'm saying since day one ( almost 2 years ago ) its way too rich ( overfueled ).
but stubbornness was real : its a vacuum leak check hose and itnake.
then after, it was : defective chinese carb get a decent brand.
i did. got an overpriced and useless Keigin, returned because why would i keep that since it doesnt fix my issue and i need the money to find what the heck is wrong.
then got a Naraku... defective and not actually new, got it replaced. same thing.
then got a glixal, one said naraku is worse than chinese ( wasted money... thats what happen when you follow zero-knowledge people advice ). same thing, but it was working a BIT better.
then after it was: its because its weirdo diaphragm carb get a dellorto.
i was stubborn to say tis not a carb issue at this point, nor a vacuum leak issue either.
let the thread die... for monmths...
played with the engine many time. foudn the micro valve elak, : its normal its not enought to cause any problem.
months after the micro leak became a stupidly huge leak. FIXED.
engine work a bit better, but issue not fixed.
asked help again everywhere, all went by : get a dellorto. only dellorto know to make a carburetor.
so i waited till i get the money to buy one. now i have one.

it made a HUUUUGE difference. now i know why so many people install phbg on 4 stroke engine under 150cc.
they seems to run so much betetr when setup properly.

now, i just need guidance about jetting according to how my engine react.
before with weirdo carb, no matetr what i did was completly useless. from 33 to 48 idle jet = no change at all always way too rich. main jet from 60 to 88, always way too rich. found oen size that would make the scooter work very badly but work, and 1 point smaller would amke it way too lean, and 1 point bigger would make it way too rich. no change at all and when there was a change it was catastrophic. all to the right or all to the left nothign inbetween.
with or withour airbox: no change at all. putting my hand on the carb to "choke"it, almost no change. barely visible change.

now with the phbg, everything change. its not enought, but everywhing change.
i put the air box on, its even richer at idle and very lean WOT. without the air box, idle is even richer but a bit richer WOT. bow it works following LOGIC. its not the case ith any of the cvk carb i have/had. no idea why tho.
i know they're hated but at this point ? no. just no.

anyway.. now i have a high quality carb, cannot return it / sell it ( wont even have 30 for it... fuck it ). sicne itsd a dellorto it will still be fine in 15 years if i ever get a wasp ( 2 stroke ). or whatever that can be fitter a 19mm.

so now i'm jsut seeking for guidance on jet sizing since i'm again low on budget, and one thing i know is that jetting is completly different between 2 different carb.

so it appear 45 idle jet is way too big, even for most 70cc 2 stroke. imagine how big it is on a 72cc 4 stroke. but this size range is what i'm seeking. 30 & 35 or 40 ? APROXIMATLY.
same for main jet. cannot really afford another set of jets as i have for my cvk ( naraku kit ), so id need a guidance for 3-4 jet size that "should" work better. not perfect but better.
its on a 76 jet and after 3/4 throttle its so lean it want to die and it make " beuhhh " like a 70's moped going from a stop.
its really too lean.
i mean i dont know how big of a difference 2 points make. so should i buy 78 80 82 or 105 106 108........... id buy 3 or 4.

depending if they're in stock locally instead of getting hard raped in the buthole by shipping and customs.
checked the cheapest option i could find for decent jet ( no chinese unknown real size anymore ), i could have 2 kit here for the price of 5 jets from the us LOL. what a beautifull world without scammers, duh....

i might try to re-fit a throttle cable to a cvk for testing purpose ( very time consuming.. id have to use another cable and extend it back using brake line since its been cut to fit the phbg without useless lenght of cable running around in the back ) to run it while i get some jets for the phbg, but i wont run cvk permanently anymore. they made me buy a quality dellorto now im stuck with it then ill run it, end of story. wont fix starting/idle issue meanwhile, but wont be so lean that it refuse to move. it will be over-rich and low power, but will move at least. WHILE I WAIT JETS !

qhile there i may verify and write down what jest its in right now on the cvk ( 33 idle for sure, cant remember for main but its the only working one )

IF i go this route temporarly, ill re-adjust the float once again. how do YOU set it ? the guide on here is pretty much useless. doesnt fit most carb i have and would either overfill the bowl or not enought so the idle jet doesnt even touch fuel. the guide was probably made using a random stock carb... those are rarely the same as the one we can buy, either replacement or performance.

[br4inl3ss]

ok i wanted to edit, but its already a long post.
anyway.

took some pics and videos.

actual float height ( the one with best result to date even tho it doesnt seems to change much much )





diaphragm noise. sounds normal as you described.



idle screw setting



mixture screw setting from fully seated



diaphragm photo



diaphragm video



cant stay running with the idle screw ( hardstop ) setting on previous video. i had to fit flat screwdriver in so it stays on.








EDIT
found an olt completly dead carburetor that had a 32 idle jet in it. cleaned, verified, isntalled.
no change, still way too rich and impossible to set idle screw properly. it must be almost completly screwed in , the spring completly squeezed. thats with the mixture screw completly seated.

[GrumpyUnk]

That diaphragm is cooked. Originally it had a 'tab' that stuck out from the outer edge and fit into the recess shown at about 7-8 o'clock. And it must sit in the groove around the outer diameter. If not, it won't seal and won't function.
The first 2 pics(CVK) look about right. The float should be about 90 to the face of the air inlet. Parallel to the floor when inverted into normal position.
The 3rd carb pic is your italian.. I think, and it appears to me to be set too low, so the fuel level would be lower in the bowl than I would have set it at.

It seems that many lose the washer and O-ring that are buried down the idle mixture port. The screw pushes on a spring, the spring on the washer and the washer on the O-ring. With parts missing, on the floor, or fallen out and never even seen, the mixture screw does not work properly. It will allow air past the threads. Threads do not seal. They will leak liquid or gas. Unmetered air can mess up the idle stability.
Are you sure the O-ring and flat washer are installed?
I did not watch the vids except the last.
tom