Real 20mm Carburetors vs fakes - with pictures

[stevec]

Hoca is not chinese or replicas of any of the other brands.
below is the address of Hoca.

6F, NO. 127, SECTION 1, FU HSING SOUTH ROAD, TAIPEI 106 ,TAIWAN
Phone:[phone] Fax:[phone]

my carb looks nothing like a Keihin internally and is a 30mm flat slide.
it is a PWK but the quality is far superior to the chinese brands.

[Lucass2T]

I think, and im pretty sure, HOCA doesn't produce anything themselves but buy from a foreighn manufacturer. Even brands like Polini outsource production. For example Polini's cylinders are made by Gilardoni and not Polini. The Malossi variators are made by TGB. Most of these companies specialize in 1 or 2 parts but offer a wide range of products produced by someone else.

And i think that HOCA buys stuff from a third party which produce copies of genuine parts.

[stevec]

still manufactured in taiwan.
i won't buy a chinese carb because they are all junk.
Hoca carbs are very good quality even if they look like other brands.
PWK carbs all look alike except some have plastic tops and some are metal.
i compared the diaphragm in mine to other brands and i can see the difference in quality.
the autochoke actually works, i tried 3 different carbs on my scooter and only the Hoca choke worked.

[humanshield]

So after the dust settles.....

Who has bought a REAL 20mm carb and where from because I'm having a really hard time finding a REAL 20mm carb.

I wish I could find a 21mm. I think that would be perfect.  I just don't wanna spend a fortune on it.

My reworked cheap chines BVH and 100cc kit aren't gonna reach their potential with an 18mm carb.

I could prolly even use a 22mm carb.

[stevec]

scrappydogscooters.com has an authentic 20mm carb, i think they also have the kit with the intake and air filter included.
you will find it under 139QMB performance.

[jc33777]

Scooterstogo has some

[stevec]

i keep forgetting to mention STG, they give discounts for people on 49ccscoot.

[larryhobman]

Do NOT buy from EVERESTPARTS248 They are fake and poor quality. I can get my motor started with fluid only and it runs great mid to upper. I have a 72cc kit 60cc factory head with the ports cleaned up intake imperfections cleaned up port matched the spacer. The cleaning up opened everything about 1mm to almost 2mm. The valves are both .005 I think the pilot section is plugged somewhere or it is the low quality of the fake that is giving me starting troubles. I am disputing the charges with PAYPAL because I did not learn about these fakes until it was too late to dispute with Ebay. Paypal gives 6 months.

everestparts248 also has a website www.everestpartssupplies.com/collections/types?page=3&q=Carburetor+-+ATV%2C+Scooter%2C+Motorcycle

They will not return my emails. DO NOT USE THEM

Just got my money back from my paypal dispute.  The seller waited until the last day that that they could respond but, paypal awarded me the victory.

[humanshield]

I just received yet another "20mm" carb.

The difference is that this one DOES have a 20mm butterfly, but it is still an 18mm carburetor on the other side of the butterfly.

I'm beginning to wonder if 20mm carbs really exist. This one is a Kehin from China.
I was really excited when I first looked at it because it does indeed have a 20mm butterfly (first one of many that were supposed to but did not.

But now it seems that even a 20mm butterfly does not guarantee a true 20mm carburetor.

This one appears to have been machined all the way from the outlet that goes into the rubber intake port all the way just past the butterfly valve. So, a 20mm butterfly valve was installed.

But from that point back to the air filter side of the venturi it takes a dramatic step down back to 18mm.

So, it STILL won't flow to the potential of a real 20mm carb as far as I know.

I'm taking this carb to a racing specialist I know locally and discuss this with them. I specifically want to ask them if there's ANY benefit to the machining and changes made to this carburetor or not.

My best guess would be that this carb (even with the 20mm butterfly) will flow no better than an 18mm carb because the carburetor venturi is still restricted to 18mm by the section untouched between the air filter side of the carb venturi and the butterfly valve.


Imagine a mile long 1 inch pipe with a 1/4 inch wide restriction down to 1/2 inch (like a small pipe within a big pipe), right at the half mile mark.  With all that 1 inch piping, it's still going to be restricted to flowing like a 1/2 pipe because of that tiny restriction.

At this point I question whether a real 20mm carburetor even exists.  Maybe 18mm and 24mm (and above) are all that is really out there for the GY6 ?   Until I see a TRUE 20mm carb for myself, it doesn't.

[scooterpimp]

Maybe its like lumber? A 2×4 is actually 1-1/2 x 3-1/2. So a 20mm is really 18mm

[humanshield]

You funny guy Mr. Pimp

Hey, Is there anyone who can send me pics of the venturi of their TRUE "20mm" carburetor so I can see it?

Still have never seen one yet.

[Silar]

Apr 8, 2015 18:44:37 GMT -5 jc33777 said:

Scooterstogo has some

It's not a true 20mm carb.  I just bought their BVH and I was thinking about buying one so I asked them about their "True 20mm Carb" and here is their response..

The venturi is not 20mm, and there is a reason for it. You need the reduced diameter to increase the velocity of the air for better fuel atomization. We recently ran a flow text and found 10% to 20% better airflow though the 20mm over the 18mm.


hmmm..

[humanshield]

That response makes no sense.

If an engine can handle the airflow, you are restricting it if the venturi is too small.

Perhaps they were speaking in a strictly stock context?

I'm am not convinced true 20mm GY6 specific carbs exist. That's why my search has evolved to a 21mm carb. I'm thinking of going with a Dellorto.

Here's an ebay listing for a 21mm GY6 carb.   It's $101.00 and I won't order it unless I can see very clear pictures of the venturi on both sides with a metric caliper up against it.

21mm ebay carburetor link

To run a Dellorto PHBG you will need to change the atomizer to a 4 stroke atomizer.
I haven't found a source for them yet.

[Scooters To Go]

The basic idea is that the Venturi accelerates the air speed, which picks up more fuel the faster it goes. However, if your exit after picking up the fuel is the same size as the small port of your Venturi, you will suffer friction loss. Because our carburetor expands the diameter after the Venturi, we don't suffer friction loss.
Atmospheric pressure is compressed from a 34mm throat to a (roughly) 16.5mm Venturi in both 18mm and 20mm carburetors. This is so that it can shoot through the center of the carb creating a suction effect that draws fuel out of the float bowl. In our design, this immediately opens to 20mm as opposed to 18mm, which allows the mixture to slow down again. In addition, by having sharp edges that the fuel passes over, it creates a swirling drag that helps pull more fuel mixture through the carb. This in addition to virtually no friction loss is why we have found to allow for 10% to 20% more airflow than a stock carb.
If calculated, a big bore engine will move air at approximately 25mph at WOT. These 20mm carbs offer an efficient limit of roughly 40mph.

Even the best carburetors in the world, such as those made by S&S, use a smaller Venturi than exit port. So the smaller Venturi, based on the best of all designs, seems to provide an effective performance function.

The only part of this carburetor that I have left to question is the sharp edge beyond the Venturi. We are looking for the proper tooling to smooth this edge and test for better airflow, which may ultimately lead to the counterproductive finding of less efficiently atomized fuel.

We have scoured the earth to find a 20mm carb with a 20mm butterfly, and to the best of my knowledge there will be no producer of a 20mm carburetor of this same design with at 20mm Venturi for two reasons. First, because of the likely performance issues. Second because it is an infeasible business idea to produce an entirely new cast for such small market demand.

[Silar]

May 19, 2015 19:38:00 GMT -5 Scooters To Go said:

The basic idea is that the Venturi accelerates the air speed, which picks up more fuel the faster it goes. However, if your exit after picking up the fuel is the same size as the small port of your Venturi, you will suffer friction loss. Because our carburetor expands the diameter after the Venturi, we don't suffer friction loss.
Atmospheric pressure is compressed from a 34mm throat to a (roughly) 16.5mm Venturi in both 18mm and 20mm carburetors. This is so that it can shoot through the center of the carb creating a suction effect that draws fuel out of the float bowl. In our design, this immediately opens to 20mm as opposed to 18mm, which allows the mixture to slow down again. In addition, by having sharp edges that the fuel passes over, it creates a swirling drag that helps pull more fuel mixture through the carb. This in addition to virtually no friction loss is why we have found to allow for 10% to 20% more airflow than a stock carb.
If calculated, a big bore engine will move air at approximately 25mph at WOT. These 20mm carbs offer an efficient limit of roughly 40mph.

Even the best carburetors in the world, such as those made by S&S, use a smaller Venturi than exit port. So the smaller Venturi, based on the best of all designs, seems to provide an effective performance function.

The only part of this carburetor that I have left to question is the sharp edge beyond the Venturi. We are looking for the proper tooling to smooth this edge and test for better airflow, which may ultimately lead to the counterproductive finding of less efficiently atomized fuel.

We have scoured the earth to find a 20mm carb with a 20mm butterfly, and to the best of my knowledge there will be no producer of a 20mm carburetor of this same design with at 20mm Venturi for two reasons. First, because of the likely performance issues. Second because it is an infeasible business idea to produce an entirely new cast for such small market demand.

Scooters To Go is right.  Not sure what we are thinking.  You have to have a Venturi that is a smaller diameter to allow the air flow to draw fuel into the air mixture.





Carburetion would not be possible if not for the venturi effect. As air travels through a carburetor, it speeds up in the section where the venturi necks down in diameter. This creates a low-pressure area, which allows fuel to be drawn into the carburetor.



Read more: www.hotrod.com/how-to/engine/0802phr-how-carburetors-work/#ixzz3afbVAB66


Looks like I'll be ordering a new carb from Scooters To Go!