PHBG tuning issue

[aeroxbud]

It is frustrating that the needle size has no direct reference to the numbers. Every time I find a needle you have to look at a chart.
They must have a secret code. 🙈

[br4inl3ss]

Apr 22, 2024 18:35:53 GMT -5 aeroxbud said:

It is frustrating that the needle size has no direct reference to the numbers. Every time I find a needle you have to look at a chart.
They must have a secret code. 🙈

Got it thanks.
I'll check this chart later.

I checked all the passage and that's the cleanest carb I've ever seen. That's probably the reason to the Dell'Orto hype....

Oh I ordered a Motoforce needle set. Should be here in two weeks. Can get them sooner for 13$ but I'm already low on $ with all I have to buy for the scooter. I just hope it's gonna fix my issues !

[thach2264]

Keep us update with your issue. I have the same issue with my 4t after 80cc bbk upgraded. bogged when revving fast and if I hold on to it, it'll died. But if throttle slowly, it'll go up to 60% then bogged again. my carb is a pd18j clone, 35 idle 88 main. have tried main up to 98 and move needle from mid to top no change. Havent try needle at bottom yet, will try.

[cagiva4ever]

Hi !

i read the Topic and looked the vids...

To verify couple things 1st, and to be Clear:
-is your intake manifold with good "bakelite" spacer and with good O-ring ? defenitely no so called "intake AirLeak" from there ?
139qmb/a is Notorious for having the bakelite to Crack and leak......


Then into PHBG 2T / 4T differences:
-"Emulsifier tube" is very different Due the fact that 4T needs alot of "Air Emulsion holes" at the tube body.
-Not only the amount/size of AirHoles, but also their location and a Group organisation, as it all plays together with Needle Position/movement, as they together determine how much and when Air is mixed into fuel to be "emulsion" together. Only after that/alongside progressively comes Venturi/Throttle slide action with AirBox induction...Mixing more air in, this is kinda 2nd stage.

AN262
moposport.fi/seosputki-an262-phbg-2-4t-dellorto/
AU262
moposport.fi/seosputki-au262-phbg-2t-dellorto/

iirc i have some Carbs where the Emulsion AirHole amount is like 30pros less, like 1 row of the holes missing.
Dont have parts in my hands to double check all details...


-Not only the Emulsifier, but also the "Sprayer" is very different among PHBG 2T vs 4T.
Because 4T version causes less negative suction/draws up less fuel from the Emulsifier into venturi area....
-This "Sprayer" plays together with Throttle slide "CutAway", as both together have an effect to the negative pressure/suction that sucks fuel/air emulsion from Emulsifier....

2T version:
moposport.fi/hajotin-phbg-au-seosputkille-dellorto/

4T version:
moposport.fi/hajotin-phbg-an-phbl-da-k-seosputkille-dellorto/


On some Dellorto versions, Air passageways at Carb body are Factory Blocked:
quote pdf:
-"To eliminate the influence of pressure pulses present in the filter box, sometimes the main emulsion air inlet is drawn from the outside by means of a connection in which we see the feed tube on the right of the carburetor. In this case the hole in the air intake is plugged."
..like at 125cc Cagiva Freccia C12R '89~'91 using PHBH28rd.

This is shown well with color photo at PDF "dellorto basic principals", page 24.
www.dellorto.it/wp-content/uploads/2020/12/dellorto_manual.pdf
www.vortex-rok.com/gestione/allegati_news_campionati/88_40.pdf

I mention this as its important to have clean good Air passageways at carb body...and later i refer more to this issue....



PHBG **AS 4T versions are also widely used with Honda Monkey mopeds 49cc 73cc 88cc 93cc etc
moposport.fi/kaasutin-phbg-18-as-4t-dellorto/

-they only have the mentioned Differences Vs 2T version being: Emulsifier, Sprayer and Jet(s) , not the needle or Throttle slide versions.
-this same ideology afaik goes also with the "PHBG 19DS racing", nothing else major needs parts change.



And yes, "Air Mixture screw" default-common setting is 1,5-turns out/open, from fully closed position. But as mentioned at topic, it can be on some machines 2,5 turn open as Default specifyed by specific vehicle W.S.M )
(Fully closed position doesnt mean brutal force, Due screw tip is tapered and very Fragile to Snap of/bend. Very Common factory issue/fail on 139 QMB/A CVK's )

-More important detail on it is to have it "Air Mixture screw" performe. If all is good a 0,5~1,5 turns is very Noticeable difference on engine behaviour, from Default opening.


People Commonly MISS-IDENTIFY Dellorto Mixture screws between Fuel-and AirMix screws.

FuelMix is located at carb manifold side, and AirMix is located at AirInbox side of the Carb body.

PHBG 19ds Racing carb has FuelMix screw
cdn.finqu.com/users/6104/images/product/21721419-19292908-img-20191022-100219-6070f4388a3f7d56.jpg
www.maxiscoot.com/fr/produit/carburateur-19-dellorto-phbg-ds-30512?vctype_id=13

Naturally these 2 Funtions work "opposite way" way regarding what happens to being Richer/Leaner.




I have personally a Genuine real "2T PHBG 19DS racing" (same exact model as linked above) , bought as new and its Mint, but i can Verify to Original Poster that something at them (all ?) is seriously wrong, a bad production batch maybe...

-in my Country, i have often heard people saying that they suffer from "Passage way issues". Apparently something is partially blocked on passage ways/bad casting mold for carb body... But nobody has yet spesifyed to me how much and where have they Bored-drilled/Dremeled material of.

i use mine at 2T engine 37cc Cagglari. My 19DS Cut's Out like hitting a KillSwitch. Where as my Chinese CLONE 4T PHBG19DS racing works perfectly on same exact engine setup-machine.
^^Notice that i have 2T and 4T Versions, and i in purpose have 4T version on the other motor as a gain performance from it being 4T version on my 2T motor....as i need it to be Lean.....at Bottom range...


As a Bike collector and mechanic i have Various different bikes-carbs-vehicles, like 50+ each, been doing this now 30+ years. i also Hobby Chinese Scooters and atv's etc PocketBikes to garden equipment everything Chinese.

For example i have a 2T Rotax Airplane carb in my 4T china Quad. im used to Mix and Match and work on hard cases with China twists...


Im saying this all "off topic" to descrive to you that i know what im doing....



There would be many other things also to Verify from you, from your PHBG 19DS, and remember that 4T behaves mainly Opposite symphtoms Vs 2T behaviour, regarding how it Manifests being Lean/Rich.

things like your carb's:
-Float Height
-Fuel Level
-Float condition
etc


im not personally YET in favour of the Needle being so wrong, but here is PHBG Needle chart:
www.mopo.fi/tiedostot/Luistineula%20W.pdf


Also remember that None of the Different Brand/Manufac Jets are exactly same size, even if both State same size. Only trust on Genuine Dellorto Jets/Parts when exactly Specifying final-working sizes. Its ok-works trouble shooting by using other brand/manufac carb parts as long as its Aknowlidged and taken into count.



I have same unfortunate experience with Native French living in France....very cocky and terrible to tech talk with as they siderail everything and then undermine all.

[cagiva4ever]

Also, have you Noticed/checked that the Connection/sealement between Carb and intake manifold is correct ?

Because there is the "lip" ring/groove.

Apparently PHBH has the correct Groove location, but as you can see PHBG 19 ds has very much different location...

PHBN
cdn.abicart.com/shop/34330/art30/h4053/178754053-origpic-9937cc.jpg?max-width=500&max-height=500&quality=85&fmt=avif

PHBG 19ds
www.maxiscoot.com/fr/produit/carburateur-19-dellorto-phbg-ds-30512?vctype_id=13

even thow CVK by photo looks seems near
s.alicdn.com/@sc04/kf/Hfb9b4c7d160641c586d3f2b9c19fbdaaA.jpg_300x300.jpg


yet again, i have no parts and measuring equipment in hand...
My neighbour town scooter kid friend uses genuine dellorto PHBN16 "from derbi senda" in his scooter 139qma, but is currently having over fuelling issues/leaking valves. If that sorts out gets Fixed, then i may check and compere hes Needle to yours....but his should be stock needle...


If that is the Case, that is a BiG NO NO, wont seal correctly....causes Mahoosive or some amount of "Intake AirLeak".....depending about intake Manifold rubber softness condition etc and We KNOW that China intake manifold rubber is HARD....

[br4inl3ss]

oh my god. thats is such an answer.
ill read it all alter.
there is NO word to thank you enought to take time to answer liek that.
extremly apreciated.

what i can say right now tho is that its built for 4t with AN parts.
this one moposport.fi/seosputki-an262-phbg-2-4t-dellorto/
and this one moposport.fi/hajotin-phbg-an-phbl-da-k-seosputkille-dellorto/
this is why i didnt buy a clone or the racing one. impossible to know with what parts they comes.
i verified and its exactly how its built with those two parts.

on the passageway issue on some phbg carb.. i checked that vicually and with a strand of wire.
absolutly nothing seems obstructive... but maybe i'm too ADHD to see it
its not installed right now so ill re-check that.

if i understand correctly, rich/lean symptoms of a 4 stroke = lean/rich symptoms of a 2 stroke ? symptoms of a rich 4 stroke are the same as the symptoms of a lean 2 stroke ?

also yes i did check. and even used a bicycle tube to seal properly. maybe its not enought tho ? to be checked later.

its good news that they should work properly on 4 stroke tho. very encouraging ! thank you very much for your reply.

[cagiva4ever]

Hi !

yes, alot of reading there, take your time, no horry, took me like 3 hours to write as English is not my native language, and i thinked hard to avoid mistakes how explaining.

Double triple check many times the carb/intake manifold sealing. As the laws of physisc apply-rule there, "rule of resistance", which goes for being electricity or air or water, all basically the same, "ALL them leak out from the place where is the lowest Resistance".

On combustion engine the Resistance varies depending how induction Suction is happening, Especially low Throttle Slide opening is much worse than WOT/more open Throttle slide position, hence carb/intake Manifold leak is very very Sensitive thing.

When opening Throttle as Slide rises, is much easyer to Suck Air through Venturi/airBox, than from THROUG peaking "hole" between carb/manifold.


You can Detect AirLeak via Spraying "Carb Cleaner / Breakcleaner spary" around the possible suspectes leaking place. Even HairSpray...
While motor idleing, and spraying said fluid around intake manifold connection, if your R.P.M's jump immediatelly by them self , its Deffo mahoosive leak...you may also twist throlttle open also couple mm's to test more.....as Suction increases....

[cagiva4ever]

Yes correct, that is the Main guide to follow keep in mind.

-"if i understand correctly, rich/lean symptoms of a 4 stroke = lean/rich symptoms of a 2 stroke ? symptoms of a rich 4 stroke are the same as the symptoms of a lean 2 stroke ?"


Some Simularitys do of course apply, but 4T is a machine to misslead...So if ever in doubt, if ever in odd situation not finding the 4T lean/rich issue cause, its Vital to remember this "opposite symphtom rule"..

Also some other things in engine's nature that cause difficulties:
-4T in example depending of engine CC, is hard to Pinpoint if its tad rich (espec big CC 4T), where as 2T spits wet fuel/oil from Silencer immediatelly or/and doesnt wanna idle when running hot temp.


There are in internet, couple privateer mx mechanic/hobbyist written "Carb guides" 2T 4T, that have good explanations of this what im talking about. its the best "2T & 4T test Track" as they jump up/down,try to accelerate right after jump landing, as FloatBowl is under full attack, where as Roadbikes do not.
Never ever seen any books about it and ive been searching the 30+ years.

[aeroxbud]

The four stroke version comes with a 40 slide, not the 30 of the two stroke version. It also has a 50 Idle jet, and a 55 Choke jet.
Wouldn't it be better to start with the carb setup fully as a four stroke carb? Even though you said a bigger idle jet made no difference. At least it might give you a base line to start with.

[br4inl3ss]

Apr 27, 2024 14:01:39 GMT -5 aeroxbud said:

The four stroke version comes with a 40 slide, not the 30 of the two stroke version. It also has a 50 Idle jet, and a 55 Choke jet.
Wouldn't it be better to start with the carb setup fully as a four stroke carb? Even though you said a bigger idle jet made no difference. At least it might give you a base line to start with.

you're sure about that ? allow me to question that one lol. the 4 stroke version comes with a 30 slide, 45 pj, 85mj. it comes from europe (bought on maxiscoot) and its exactly the same available in the US/CAN. i verified all that with 2 stroke shop (propartscoot, scooterswapshop, scootertuning, VTT Lachute,

ADM Sport). they vomit when i said it was on a 4 stroke, but they all agreed my phbg is the 4 stroke version and the only one spread across the country (canada) no matter where is comes from. scootertuning opened 2 "openbox" phbg just to be sure it was the same setup as mine.

[aeroxbud]

Here is the link from the Dellorto store. www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/complete-carburettors-dellorto-motorcycle-carburettors-parts/phbg-15-to-21mm/r2507-dellorto-phbg-18as/

[br4inl3ss]

ah i see it a different model. 18 AS... mine is a 19 DS. that may be why.
this ref is 2507, mine is 2631.

when refering to 4 stroke, im refering the same as the whole planet AKA the phbg DS which comes with 4 stroke atomizer and the other part i dont remember the name. they swap them out for the 2 stroke parts.

anyway no one ever use this model here. they only talk avec the 15 DS, 19 DS, 21 DS. the STANDARD carb.

www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/complete-carburettors-dellorto-motorcycle-carburettors-parts/phbg-15-to-21mm/r2631-dellorto-phbg-19ds/

now for the intake... i checked to get a gy6 125/150cc intake or the 139qmb naraku intake that are far superior.... but its 33mm. aint gonna fit at all.
my phbg intake connection size is 25mm. stock 139qmb size is 28mm. and others are 33 to 35mm depends on brand it seems.

they're similar as far as groove goes.

and the inside of the intake

[cagiva4ever]

Hi !

i bet my money on the Intake/Carb connection AirLeak, as per ive explained. Grooves look simular, but too many Variables on the issue...On the video it also shows that carb Rattles/moves alot, causing even more worse AirLeak id say, no matter if bicycle tube rubber between as insulation/filler.
(Can you diy/custom make "adapter" ? that would make both ends Seal properly.... short metal pipe and a suitable short rubber hose part around....)

All symphtoms point to it and those "mechanical-tangible" things....

[br4inl3ss]

Apr 28, 2024 14:13:36 GMT -5 cagiva4ever said:

Hi !

i bet my money on the Intake/Carb connection AirLeak, as per ive explained. Grooves look simular, but too many Variables on the issue...On the video it also shows that carb Rattles/moves alot, causing even more worse AirLeak id say, no matter if bicycle tube rubber between as insulation/filler.
(Can you diy/custom make "adapter" ? that would make both ends Seal properly.... short metal pipe and a suitable short rubber hose part around....)

All symphtoms point to it and those "mechanical-tangible" things....

first, thanks alot.

i'm trying to mane an adapter but not 100% sure ill be able to.

its almost finished i have to remove the rest on a wirebrush.
the problem is gonna be the hose/rubber/silicone part.... hard to get here without spending like 40$.
ill walk around to see if i have somethign of that size.... tbh i have high quality silicone coupler from when i was doing turbo installs, but they're way too big.

the size is the problem.

before that i tought about getting the naraky intake or a gy6 125/150cc intake but they're even bigger (33mm), no go.

EDIT :

finished

well.. wont last, but enought to try. old grip.

[cagiva4ever]

Hi !

thx for sample photos and great effort. To me personally the 2 videos of yours and those photos make it all up, worth to me as data, which can be used to help also others.

Ive never seen Scalped/stripped gy6 oem intake manifold before (or is that Naraku made?)


A Hydraulic hose from Tractor etc scene, should work good as its oil/chemical resistant. Can also be bought as per wanted lentgh (price per meter, so to speak)
id imagine a short peace would cost couple dollars... or can be obtained free from helpfull service carage scrap yard...later.

as like you said, now your testing to be absolute sure....

thumps up ! we keep fingers crossed.


As a info detail, when Intake Manifold AirLeak appears at low rpm's (when suction into emulsifier is relatively weak), it Creates total Collapse/Override's the Emulsifier Suction function, hence engine sounds like in your Vid. At higher rpm's starting from Main Jet, the Throttle slide is a lot more open and during that the Emulsifier/Needle is much more open -> can deliver great amount of fuel EVEN that there would be still "Minor" intake airLeak at same time happening.

If this would be 2T, you would notice very slow r.p.m drop (rpm's hanging up) due the AirLeak, but as its 4T it doesnt symphtom as easyly as 2T due the engine nature... (very slow rpm drop/hanging up rpm's when "Coasting" down from Main Jet into Idle Jet circuit)

on a 4T, a serious Airleak can also behave like Hitting Kill Switch, engine goes totally dead like missing Sparg complitely, until Throttle is complite released and again slowly open up again. Happens when the "rule of resistance" parametres occure.
on my 200cc ATV, i had 0,35mm airgap between intake manifold/cylinder surface (thx to ex owner), and i got that behaviour as explained. ex-owner had metalfiled the intake manifold and Scratched cylinder metal surface, i was able to stick in 0,35mm feelercauge at 1 point around the intake manifold sealing area..Now the Airleak is fixed and i need to down jet like 20~25 sizes on my Main jet, ex had Compensated the unsolved issue by putting in a bigger mainjet...
**This concerns also you, most likely you need to downjet some, if/after your find Airleak from yours, size-amount depends on carb manufac i.e worst opponents are Dellorto Vs Mikuni as they 2 have totally different Ideology how to Determine jet size (dellorto is basically very near Metric and Mikuni uses complite different ideology. its like compering Kilograms against speed.
On a Mikuni jet size #300 equals Dellorto #150 jet size, roughly +/-~5 numbers....


As a sidenote, to be sure-clear, have you checked Visually that the "FuelMix Screw conical shaped end-tip" is perfect shape ? no factory error...
im just making sure all details are good...