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Post by tocoo on Apr 25, 2018 5:46:18 GMT -5
On my [non-stock] PD18j carburetor with black lid and the accelerator pump, I ripped a bit of the head of the atomizer because I did not have the wrench to remove it. The head of this atomizer is special because it is not hexagonal so only a open wrench of 7mm can unscrew it.
I decided to replace this atomizer by an atomizer form a repair kit, but the repair kit is for the PD24 carburetor. THe two atomizers are nearly identical, perhaps the thread of the new one is 1mm longer.
Long before I replaced the atomizer, I replaced the original 30 idle jet by another one which sits slightly lower than the original. I had no problem with this new idle jet.
Long before I replaced the atomizer, I also changed the main jet without problem.
Here is the timeline:
''stock configuration'' : idle jet = 30, main jet = 76. the original atomizer and idle jets have dents at their heads due to me
=>no problem, idle at 2000 RPM
''stock configuration with new jets'' = original atomizer, main jet = 80 , new idle jet = 30
=>no problem, idle at 2000RPM
configuration after the replacement from the repair = new atomizer, new ''piece which sits below the atomizer'', original main jet = 76 , original idle jet = 30
=>idle at 2800 RPM
My problem is that the idle with the ''configuration after the replacement from the repair'' is at 2800 RPM, even when the idle screw is totally unscrewed.
Once I saw this, I put back the stock configuration and I managed to get the idle at 2000 RPM again.
Is it possible that the atomizer changes the idle this much ?
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Post by GrumpyUnk on Apr 25, 2018 10:37:27 GMT -5
Is the 'atomizer' you refer to the tube that the main jet is screwed into? The ones I am familiar with have what I call and 'emulsion tube' that the main jet screws into. It has a hole through the centyer, and multiple drilled holes in the 'upper' section. The fuel comes up through the jet from the float bowl, through the center of the 'emulsion tube', and when it gets to the holy part, air comes in and mixes with the liquid fuel, forming an emulsion. This bubbly mixture is then drawn up around the needle jet and into the venturi.
The tapered needle, operated by the diaprhagm & vacuum on one side, pulls the needle out of the 'needle jet', which is above the top of the emulsion tube. The needle jet should be removable by pressing on its top surface, I expect by going through the diaphragm slide hole, (diaphragm & slide removed). It is a press fit, I think.
If you are unable to get your idle below 2800, then check that the butterfly or throttle plate is being allowed to go closed, or very close to being closed. It is possible it is warped or bent.
The 'idle screw' referenced could be the idle mixture screw or the throttle stop screw(on the linkage above where the cable 'slug' connects) on the opposite side. I don't know which.
If the emulsion tube is longer(atomizer threads) the atomizer top end could push things out of place, such as the needle jet, or the needle itself, which could push the slide up.
tom
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Post by cagiva4ever on Apr 25, 2018 16:10:07 GMT -5
"tocoo" take a very close and accurate comparison of the 2 Atomizers/emulsifiers/Nozzle for Needle....
if they are not 100% identical then this can happen:
-total lenght of the Atomizer:
too short or too long will have an effect into "static fuel pressure" , which means Richer or leaner depending being longer or shorter. same effect as Altering Float height/fuel level. Due jet "swimming being deeper" or viceversa in the FloatBowl.
-Outlet shape of the Atomizer. I.E 2T version versus 4T version.....
- Emulsion (air) holes at Atomizer body: their location and amount/size determines the rpm range when they are effective....various details regarding how they effect...
1 simple check regarding Emulsion holes, very basic is to check their Diameter and amount to Match Vs Stock specs. once again, smaller holes cause richer Mixture as Less air into mix and viceversa. same effect for amount of the "Emulsion Air holes".
Be accurate, be aware realise, that for example "Float Height/Fuel level" adjustments fine tuning is done in like 0,1mm amounts.
also, are you sure that your Throttle slide or/and diaphram wasnt acting up ? before you but back all the original parts....
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Post by tocoo on Apr 26, 2018 8:40:01 GMT -5
Yes I was careful with the position of the throttle cable and I installed several times this carburetor modded with the new atomizer. I use the vocabulary from here www.49ccscoot.com/faq/carbtune.html#needinfothe atomizer has a separated little seat on which it relies [once everything is installed; it goes like this : seat of the atomizer then atomizer then main jet. length of new seat+new atomizer = 37,99mm length of original seat+original atomizer = 38,33mm length of new atomizer = 26,50mm length of new seat = 11,49mm length of original atomizer = 27,02mm length of original seat = 11,51mm I tried the old set+new atomizer and the idle is also too high. Only the original seat+original atomizer allows a good idle. This this repair kit is not compatible at all. The diameter of the plunger is 18mm, whereas the diameter of this carburetor is 16mm. THe only thing I could use form this kit is the mixture screw. What I do not understand is that there are plenty of repair kit on ebay but there does not seem to be a way to determine beforehand if a kit is relevant for the carburetor. I think the only way to be sure is to stick to one manufacturer for the carburetor and then the repair kit when needed. There is a brand KELKONG or GOOFIT on aliexpress which sell those gy6 carburetors and, since my the carburetor sold with my scooter works well now, the next time I need a carburetor will be from such a seller who sells the carburetor and the spare parts like jets and repair kits |
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Post by GrumpyUnk on Apr 26, 2018 9:15:21 GMT -5
tocoo:There is a brand Kelkong on aliexpress which sell those gy6 carburetors and, since my the carburetor sold with my scooter works well now, the next time I need a carburetor will be from such a seller who sells the carburetor and the spare parts like jets and repair kits
I have seen 3-4 brands that care enough or are proud enough of their quality and workmanship to have their name case into the side of the body, partially hidden under the cable linkage bracket.
I do not know how a 'repair' or 'rebuild' kit can fit them all properly.
I just read the carburetor FAQ and the explanations. If you noodle for a second, having a different length atomizer/emulsion tube will change the area exposed to incoming air... more holes possible in a 'longer' tube. That will fiddle with what is pulled up around the needle(at idle...? I think so), so your idle speed will be affected as the needle and slide can only go so far/deep into the nozzle & atomizer. and then they stop. In short, to be doing an apples to apples comparison, you'd have to make sure the parts are the same size, and changing the length will have to change the operating range of the carburetor -i.e., the volume it will handle from idle to full speed. Longer or shorter will affect the volume of fuel/air mix being allowed in at a given venturi velocity. Carburetors are sort of like black magic or voodoo, and some designers can make them sing and dance, and others leave you with a very finicky carb, touch this 1/8 of a turn and it won't start, turn that 1/4 of a turn and the top speed drops by 20%. Theyz difficult to meddle with successfully, especially when you are pulling parts from eleventeen manufacturers, and expecting them to be the same. They are not.
It seems that sometimes it would be worth while to just put the old one in the spares bin and buy a new carb. I do think there are some quality carburetors on the market, you just have to find them. A good carb should start and run right out of the box, with minimal adjustment necessary for proper idle quality and speed, and reasonable higher speed performance. No sags, no bogs, no stutter or hesitation when accelerating a warmed up engine. From cold, a bit of gentle use as it warms up seems appropriate to me, so I don't expect perfection from cold, but do expect quick start & faster idle cold.
tom
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Post by tocoo on May 3, 2018 9:29:36 GMT -5
now the carburetor has a high idle speed even with the original main jet and the original idle jet.
THe only unusual thing I recall doing is that I cleaned the accelerator pump for the first time [components are: a very small o-ring, a cut jet, a very small metallic ball, a very small spring and a membrane with a long stick] and I cleaned the whole carburetor with starting fluid instead of carburetor cleaner.
I hope I did not bend the plate of the accelerator. I will clean the carburetor again.
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Post by cagiva4ever on May 3, 2018 14:41:59 GMT -5
So, are you still using Miss-Matching carb parts 2gether ? i.e wrong type of Atomizer ?
just in case, did you harm any diaphrams with the "starting fluid/carburetor cleaner" ?
acceletator pump action/functioning you should visibly test and eyeball Via AirIntake side when AirBox/union tube removed from carb. That will of cource make some things worse like idling etc non-steady rev's... but at least you can test Accelerator pump functioning....see a youtube vid if needed...
absolutely verify No Airleaks and No diaphram/throttle slide issues from existing...
You could also test the Throttle slide/diaphram opening and closing properly with a mild vacuum from "hoover" Via connected into CVK's outlet side (loose carb in your hand) , vacuum suction on/off.
take out complitely the "Mixture screw" and check its tip shape...
any Pro, when ever handling Carb what ever carb would always also check the static "Float height", even thow it isnt your source issue, but all basic specs need to be checked verifyed always.
1 single problem as a variable like AirLeak/vacuum or a genuine multi issue problem, difficult to speculate as topic lacks alot of data.
most variable thing atm your doing is removing and re-attaching the carb, as far as not touching any adjustments that would change.
just in case to clarify, you havent changed the PD18J original float with the pd24 kit Float ? if it had one included, not mentioned.....
Float(s) always have to be Carb matching specific weight in grams, to get correct Fuel level/static fuel pressure... Usually, larger the carb, heavyer the float(s) -> richer mixture.
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Post by tocoo on May 5, 2018 1:59:59 GMT -5
currently all parts were original on the unbridled carburetor. I did not even tried the float of the PD24j. THe accelerator pump works well indeed.
Last time I could manage to get the low idle with the original parts of this carburetor, but as soon as I installed the seat to the scooter, the idle raised to 3000 RPM. It turns out that my seat touches the auto-choke and presses it down on the carburetor. The idle always rises when I put the seat back on the scooter, but the rise is generally around 2200 RPm, not 3000 RPM.
Once the seat was removed again, I tried to unplug the auto-choke a bit but the idle was still high.
I tried to swap this original auto-choke with a brand new one and the idle was still high.
This is the test of the auto-choke:
auto-enricher from the unbridled [black lid] carburetor
ohms in retraction before the erection = 8,9ohms
time to erect [hot] = 2min
ohms in erection [hot] = 4,2 ohms
time to retract [hot->cold] = 6--7 minutes
ohms in retraction [hot->cold] = 5,7 ohms at 7 minutes ; 6,2 ohms at 9 minutes ; 6,7 ohms at 12 minutes ; 7 ohms at 14minutes ; 7,3 at 17 minutes ;
auto-enricher brand new from aliexpress
ohms in retraction before the erection = 15 ohms
time to erect [hot] = 2min
ohms in erection [hot] = 10,6 ohms
time to retract [hot->cold] = 7--8 minutes
ohms in retraction [hot->cold] = 12,3 ohms at 7 minutes ; 12,4 ohms at 9 minutes ; 12,7 ohms at 12 minutes ; 12,8 ohms at 14minutes ; 13 at 17 minutes ; 13,1 ohms at 20 minutes
I will install the brand new autochoke on this unbridled carburetor after I clean everything.
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Post by cagiva4ever on May 5, 2018 9:07:17 GMT -5
WTF, that is an weird issue E-choke hitting seat cowl....
so both of your E-chokes are hitting the seat ? the original Pd18J and this AliExpress version ?
you originally didnt have any issues with the scooters original e-choke hitting seat ?
- are both E-chokes defenitely properly Deep enough in the carb body ?
- have you checked that both e-chokes have same diameter profile Needle, and that Needle is in same Depth cold/hot , in millimetres..
as i have said on other topics, some E-chokes have adjustable Needle, etc differences.
-you could also take Of the protective loose Cover from the E-choke, to get more room clearence to avoid hitting Seat, in a case if its a matter of millimetres...
Basically sounds like the E-choke is active Due needle not closing carb channel properly deep enough... or the chokes piston/plunger is sticking jamming when attached into Carb.....
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Post by GrumpyUnk on May 5, 2018 9:34:55 GMT -5
I would like to see a picture of the carburetor and choke in place. It is possible the seat bucket presses on the choke, or is moving something else to raise the idle speed.
Pressing on the choke should actually try to rotate the carburetor in the rubber connectors. I think the bucket may be pressing on part of the throttle linkage. Or not.
tom
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