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Post by GrumpyUnk on Aug 14, 2020 10:35:05 GMT -5
If you want to compare... size... then pull the slide from the carbs to be compared, get out the micrometer, and measure their diameter. Bigger slide wins. IF, the venturi size inlet accommodates the diameter of the slide, that is.
I have seen(in hand) several different slide diameters for carbs rated to be the same size. I do not think there is any way they both could flow the same mass of air in duplicate conditions.
I kinda gave up looking down the outlet of these CVKs as the diameter could be larger in one, but the slide diameter(thus venturi) could be smaller than another(with smaller outlet diameter). Chinee wiley sales person figure customer want big outlet, give big outlet, satisfy customer, make money, go home to wife...
Oh, wait! The cows are coming home, I have to run......
tom
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Post by dexameth on Aug 14, 2020 11:39:33 GMT -5
If you want to compare... size... then pull the slide from the carbs to be compared, get out the micrometer, and measure their diameter. Bigger slide wins. IF, the venturi size inlet accommodates the diameter of the slide, that is. I have seen(in hand) several different slide diameters for carbs rated to be the same size. I do not think there is any way they both could flow the same mass of air in duplicate conditions. I kinda gave up looking down the outlet of these CVKs as the diameter could be larger in one, but the slide diameter(thus venturi) could be smaller than another(with smaller outlet diameter). Chinee wiley sales person figure customer want big outlet, give big outlet, satisfy customer, make money, go home to wife... Oh, wait! The cows are coming home, I have to run...... tom CVK carbs don't have a slide, but a butterfly and yes measuring the butterfly is the correct way to do so... But CVK carbs are not bored all the way thru like PHBG or PWK carbs. Cheap carb companies use the same slide in the same body, just bore the body to match. Sometimes in smaller carbs we find the slide much wider than the bore, with grooves on either side and that could create turbulence... Lots of factors with these carbs... |
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Post by GrumpyUnk on Aug 15, 2020 10:26:04 GMT -5
Well, what do you call the cylinder that moves up and down via the vacuum diaphragm except 'slide'? I don't know the other name, but a search for CVK image returned a lot of pictures that show the same dang carb that comes on these machines(for the most part- at leas the ones looking for a 20mm or 19mm size).
I suppose the flat plate in another style carb is also called a slide...
So, what is the answer? What is the 'technical term' that I missed?
I'll repeat, the vendors diddle with the carbs, and make them 'appear' to be what the customer is looking for, whether that helps or hinders is another question. They go home to Mama and eat dinner either way, happy to take your money.
tom
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Post by dexameth on Aug 15, 2020 11:43:20 GMT -5
Well, what do you call the cylinder that moves up and down via the vacuum diaphragm except 'slide'? I don't know the other name, but a search for CVK image returned a lot of pictures that show the same dang carb that comes on these machines(for the most part- at leas the ones looking for a 20mm or 19mm size). I suppose the flat plate in another style carb is also called a slide... So, what is the answer? What is the 'technical term' that I missed? I'll repeat, the vendors diddle with the carbs, and make them 'appear' to be what the customer is looking for, whether that helps or hinders is another question. They go home to Mama and eat dinner either way, happy to take your money. tom Ahh yeah I looked past that haha whoops. The vacuum slides are totally different sizes you're right. But, it doesn't stop there... Why are some slides flat bottom and others curved? Does the curved, or cutaway, slides allow more air? People knit pick these carbs so bad. Bottom line is the 20mm carbs are larger than stock. |
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Petro
Scoot Enthusiast
Posts: 149
Location: Gothenburg, Sweden.
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Post by Petro on Aug 24, 2020 3:17:54 GMT -5
Naraku NK200.01, Supposedly 20mm, 18mm IRL.  EDIT: Answer from Naraku: Dear Petro, i just checked with R&D dept. the V.3 version of nk200.01 is 18mm. The v2 version used to have 20mm but the carb was difficult to set up and no power increase. Thats why its changed to 18mm in the latest version. We will inform our distributors to check their descriptions. thank you! |
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Post by averagejoe on Oct 9, 2020 16:14:30 GMT -5
Hi,
New here. And am glad I read this thread.
I was just ripped buying a 20mm carb. It has a 20mm butterfly but, just past the butterfly the machining stops and goes thru a bore that must be more than 2mm smaller.
I measured the CV piston (or slide) and it measures just under 18mm.
How do you plug a 18mm hole with a 17.9mm piston?
pulled out a few 18mm carbs and they all measure the same 17.9mm
this all using beat up SAE dial calipers (.705) and metric conversion. (17.907)
Like stated before - YMMV
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Post by CrankingWithCG on Oct 12, 2020 1:42:45 GMT -5
So, the real question, can you run a big bore GY6 50 on an 18mm carb and get full power? Or just skip the stress and go to a 21mm pwk?
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Petro
Scoot Enthusiast
Posts: 149
Location: Gothenburg, Sweden.
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Post by Petro on Oct 27, 2020 2:22:00 GMT -5
So, the real question, can you run a big bore GY6 50 on an 18mm carb and get full power? Or just skip the stress and go to a 21mm pwk? Yes. A 18mm is enough, I am running a 20mm Mikuni 2-stroke right now and besides that it accelerates faster of course and it's stronger there's no real higher top speed, I just get there faster... All to the cost of 30-80% higher consumption. But it is funnier to ride though... |
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toto50
Scoot Enthusiast
Bring the Motherf***king Ruckus!
Posts: 111
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Post by toto50 on Aug 19, 2021 12:10:55 GMT -5
Where can I buy a real 20mm carb for my gy6 50cc with no fuss?
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Post by scooter7878 on Aug 31, 2021 20:50:45 GMT -5
Everyone should just save there 30 bucks in all these 30 dollar 18,19,20 mm ?able carbs and buy a oko 21mm flat slide carb for 70 bucks and find out what real power is and not have to bother worrying about if it's 20mm or not. The power gain from a flat slide carb is imo almost as much as going from a stock 50cc to a 50 mm bbk kit. It's un believable the gain. By the time u bought 2 ?able 20mm carbs u could have bought a oko and been done with twice as much power and way way better throttle response
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Post by steve1297 on Oct 18, 2021 23:38:09 GMT -5
If you have a 52mm BBK , some of the heads have over a 21mm intake port. I use a 26mm PWK with great results. It will smoke a 24mm CVK. Power gain is incredible
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Post by scooter7878 on Oct 19, 2021 0:33:07 GMT -5
If you have a 52mm BBK , some of the heads have over a 21mm intake port. I use a 26mm PWK with great results. It will smoke a 24mm CVK. Power gain is incredible I got a 50mm and a stroker with a 21mm carb I'm wondering if I'd get better power with a 24mm I'm wanting to try it |
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Post by steve1297 on Oct 19, 2021 2:04:28 GMT -5
If you have a 52mm BBK , some of the heads have over a 21mm intake port. I use a 26mm PWK with great results. It will smoke a 24mm CVK. Power gain is incredible I got a 50mm and a stroker with a 21mm carb I'm wondering if I'd get better power with a 24mm I'm wanting to try it I think so. There's a noticeable difference between a 21 and a 24 on mine. I started with a 21, worked up to a 26. |
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Post by dexameth on Oct 19, 2021 2:58:12 GMT -5
If you have a 52mm BBK , some of the heads have over a 21mm intake port. I use a 26mm PWK with great results. It will smoke a 24mm CVK. Power gain is incredible What's your setup? More curious as to jetting. |
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Post by steve1297 on Oct 19, 2021 3:00:53 GMT -5
If you have a 52mm BBK , some of the heads have over a 21mm intake port. I use a 26mm PWK with great results. It will smoke a 24mm CVK. Power gain is incredible What's your setup? More curious as to jetting. 110 main. 35 idle. 52mm BBK. Long case. I get way better results with the Bando 723-17.5-28 belts. Naraku variator. Naraku drive face. 7g rollers. Yellow contra spring |
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