On the remote primer, the small barb draws vac when released and the longer one is a return to the tank. When you push the bulb down it helps pressurize the fuel tank to assist the inlet side of the circuit.
Not exactly. It’s actually pulling fuel through the carb. Hence why his gauge dropped each time he let the primer out. Yes it then pushes fuel back to the tank via the return line, but it’s the same volume as what it just pulled from the tank, thus not adding pressure. This is a misconception a lot of people have about two stroke cube carb systems. I think it’s because often when the fuel cap is opened it releases pressure. The pressure is just caused by heat or agitation of the fuel and the fact that the tank only vents in and not out (the volume of fuel being used has to be replaced with something but you have to be able to operate the equipment in any orientation without fuel leaking all over. Think chainsaw) Another test I perform after bleading down the pressure with the primer is to switch the pump over to vacuum and draw a vac through the carb with the primer. That checks the same seals and valves but in the opposite direction.
very clear video on pressure testing a carb, thank you. The mityvac seems like a good tool and worth getting, but I might try and rig something up with small tubing and a balloon (or similar) for now.
The Mityvac costs $120. If you were going to test a lot of carburetors in a small business it might be worth it. Otherwise you could make your own test tool for a lot less.
I have the same tool and have used it to test for leaking crankcase seals using the appropriate blanking plates and gaskets, vaccum testing for air leaks of the seals. Difficult starting can be caused by air leaks here, and four stroking.
One thing that should be noted is make sure your test fuel lines are the proper size. Iv'e had tests where they showed pressure falling and found it be leaking there.
thanks, just ordered a mv8500 for testing leak down on a snowmobile rebuild. Good to see this as I have a couple carbs on some saws to go through as well.
You probably won’t see this but could you just hook your tester right to the carb port that goes to your purge bulb to test the check valve in the carb? Just so you eliminate the bulb itself as being an issue.?
If it is leaking out the air filter it is probably the needle and seat not seating. If it is coming out the bowl or the bowl nut it is the gaskets. Good luck. Thanks for watching.
Good video, but there are a couple of mistakes in your understanding of how the primer bulb works, and what we see with the tests you did on the primer bulb towards the end of the video. The last two tests only proved that the return hose was good, and the check valve in the primer wasn't leaking backwards.
Great instructional video! Fortunately you had a spare gasket that was able to fix it. I bought a rebuild kit for $13 installed it in my Walbro WT324 carb and it still flooded my chainsaw. I could have used that money to buy a new carburetor. From now on, if the carb leaks when tested, it gets scrapped and I buy a new carburetor. I'm glad I didn't blow over $100 on a Mity Vac.
thanks for the tips (pun intended) I went ahead and ordered a mity vac like yours. my question is that I may have fuked the existing needle with my ultrasonic, I didn't know that it should be removed. so now under pressure, the movement of the needle has no effect It leaks bad enough to be audible should I have removed it before US cleaner
DW6 I performed the test on the metering side where u said if it leaks you have a bad check valve. I actually have a very slow leak on that side. When the seedeater is running I slowly will hear it losing power while idling until it dies, just as the test shows. I have to adjust my low needle often because of this. My educated guess is the low idle check valve has a leak because the gaskets are new and I didn't find bubbles in that area. What do you think ?
Are you saying the primer side draws air from the tank? Isn't the primer side the fuel return line. When i pump my primer bulb air then fuel is returned to the tank. my primer bulb is attached to the carb.
What can I do if I pump pressure and I press pressure bulb and pressure does not move down at all,bulb is good does that mean needle seat is no good and I should buy new carb or can I fix it somehow
A primer bulb does not 'suck air from the top of the tank'. It sucks gas from the tank... THROUGH the carberator. It then dumps the excess gas into the top of the tank. If your primer bulb has gas in it, then you know that the carb has gas in it.
Correct ~!~! The primer bulb pulls gas from the tank into the carb priming it with fuel, "Hence Primer Bulb" and then dispensing the extra fuel into the tank.... Filter line to the pump side of the carb... The side with the ONE BIG screw in the middle, then the other line comes from the carb to the primer bulb then the short line from the bulb to the tank to empty the excess fuel so the carb doesn't flood .............. That is where many people people get confused on the routing of the fuel lines when they work on their saw or weed whacker that has rotted lines that are no longer intact....... There are videos on you tube that show the wrong way to hook up fuel lines.... Some vids show the line from the tank to the primer bulb then into the carb NOPE wrong configuration .... Plus Tard Mon Ami ....
You can try stretching the spring a little bit and test the pop off pressure. If it leaks off, the needle could be bad. If you replace the needle & gaskets and it still leaks down the needle seat is probably bad. You'can't replace the seat so if that's the problem the carb is scrap and you wasted your money on a rebuild kit. You can buy a new carb for the price of a Walbro rebuild kit so you're better off buying new carb if you can't get the needle to seat.
The problem with vacuum testing these parts is that you're pulling the parts together on the gaskets making a better seal. A pressure test would push against the needle and gaskets allowing for a truer test.
yall ever thought about buying a 10.00 manual pump blood pressure cuff and just pulling the hose off the cuff sticking it to the carb? lol after your done you can also check your blood pressure
doublewide6 já vi que dá prá usar na reparação de roçadeiras e motosseras e motos também.foi uma luz em alguns defeitos de difícil diagnóstico. só estou aguardando a visita do representante.
thanks, just ordered a mv8500 for testing leak down on a snowmobile rebuild. Good to see this as I have a couple carbs on some saws to go through as well.
@@MOAArtstore going through the auctions on ebay it looks like it comes down to the accessories... the 8000s are listed as vacuum pumps... and after all its in the brand name too
![GEEK TIMË [OFFICIAL AUDIO]](http://i.ytimg.com/vi/ry-6RvkH880/mqdefault.jpg)
8:00 you're not pumping air in there. You're sucking air out of it. Thank you for the video. I really appreciate 💯
On the remote primer, the small barb draws vac when released and the longer one is a return to the tank. When you push the bulb down it helps pressurize the fuel tank to assist the inlet side of the circuit.
Thnx I learn something from you
Not exactly. It’s actually pulling fuel through the carb. Hence why his gauge dropped each time he let the primer out. Yes it then pushes fuel back to the tank via the return line, but it’s the same volume as what it just pulled from the tank, thus not adding pressure. This is a misconception a lot of people have about two stroke cube carb systems. I think it’s because often when the fuel cap is opened it releases pressure. The pressure is just caused by heat or agitation of the fuel and the fact that the tank only vents in and not out (the volume of fuel being used has to be replaced with something but you have to be able to operate the equipment in any orientation without fuel leaking all over. Think chainsaw)
Another test I perform after bleading down the pressure with the primer is to switch the pump over to vacuum and draw a vac through the carb with the primer. That checks the same seals and valves but in the opposite direction.
Small cube butterfly carbs should not exceed 7 psi for pressure testing, 10 psi for rotary valve carbs....
very clear video on pressure testing a carb, thank you. The mityvac seems like a good tool and worth getting, but I might try and rig something up with small tubing and a balloon (or similar) for now.
The Mityvac costs $120. If you were going to test a lot of carburetors in a small business it might be worth it. Otherwise you could make your own test tool for a lot less.
I have the same tool and have used it to test for leaking crankcase seals using the appropriate blanking plates and gaskets, vaccum testing for air leaks of the seals. Difficult starting can be caused by air leaks here, and four stroking.
One thing that should be noted is make sure your test fuel lines are the proper size. Iv'e had tests where they showed pressure falling and found it be leaking there.
thanks, just ordered a mv8500 for testing leak down on a snowmobile rebuild. Good to see this as I have a couple carbs on some saws to go through as well.
You probably won’t see this but could you just hook your tester right to the carb port that goes to your purge bulb to test the check valve in the carb? Just so you eliminate the bulb itself as being an issue.?
10 PSI is a bit high for diaphragm carbs. 7 PSI is a bit safer. Nice video.
Excellent education....can you tell me what ultrasonic cleaner you use and a video on how far you break the carb down would be greatly appreciated
That's a good setup you got there
Are you using vacuum or pressure for this test....and can vacuum alone be used if you dont have a pressure feature on the vac. tool?
If it is leaking out the air filter it is probably the needle and seat not seating. If it is coming out the bowl or the bowl nut it is the gaskets. Good luck. Thanks for watching.
Great video. Exactly what I needed to know. I have the same carb on my Homelite chainsaw. Well done!
Good video, but there are a couple of mistakes in your understanding of how the primer bulb works, and what we see with the tests you did on the primer bulb towards the end of the video. The last two tests only proved that the return hose was good, and the check valve in the primer wasn't leaking backwards.
Great instructional video! Fortunately you had a spare gasket that was able to fix it. I bought a rebuild kit for $13 installed it in my Walbro WT324 carb and it still flooded my chainsaw. I could have used that money to buy a new carburetor. From now on, if the carb leaks when tested, it gets scrapped and I buy a new carburetor. I'm glad I didn't blow over $100 on a Mity Vac.
thanks for the tips (pun intended) I went ahead and ordered a mity vac like yours. my question is that I may have fuked the existing needle with my ultrasonic, I didn't know that it should be removed. so now under pressure, the movement of the needle has no effect It leaks bad enough to be audible should I have removed it before US cleaner
If you haven't bought a pump yet, get one that tests pressure and vacuum. They come in real handy.
Good job Numero uno
DW6 I performed the test on the metering side where u said if it leaks you have a bad check valve. I actually have a very slow leak on that side. When the seedeater is running I slowly will hear it losing power while idling until it dies, just as the test shows. I have to adjust my low needle often because of this. My educated guess is the low idle check valve has a leak because the gaskets are new and I didn't find bubbles in that area. What do you think ?
I have to do this on my pressure washer carburetor. I have a major gas leak. Thanks for the video.
Excellent video bro thank you for making it so clear
Great video DW6, thanks!
Are you saying the primer side draws air from the tank? Isn't the primer side the fuel return line. When i pump my primer bulb air then fuel is returned to the tank. my primer bulb is attached to the carb.
That was really nice of him.
Taking the time to check for leaks is most important
Excellent Video, nice and systematic!
Excellent video! Thanks for sharing.
Second Amazon link points to the first one, Trimmer line.
What can I do if I pump pressure and I press pressure bulb and pressure does not move down at all,bulb is good does that mean needle seat is no good and I should buy new carb or can I fix it somehow
Excellent video and presentation, thank you.
When you press the primer the needle does not open, it opens on vacume return sucking the diaphram down opening the needle to allow fuel flow
A primer bulb does not 'suck air from the top of the tank'. It sucks gas from the tank... THROUGH the carberator. It then dumps the excess gas into the top of the tank. If your primer bulb has gas in it, then you know that the carb has gas in it.
Correct ~!~! The primer bulb pulls gas from the tank into the carb priming it with fuel, "Hence Primer Bulb" and then dispensing the extra fuel into the tank....
Filter line to the pump side of the carb... The side with the ONE BIG screw in the middle, then the other line comes from the carb to the primer bulb then the short line from the bulb to the tank to empty the excess fuel so the carb doesn't flood ..............
That is where many people people get confused on the routing of the fuel lines when they work on their saw or weed whacker that has rotted lines that are no longer intact.......
There are videos on you tube that show the wrong way to hook up fuel lines.... Some vids show the line from the tank to the primer bulb then into the carb NOPE wrong configuration ....
Plus Tard Mon Ami ....
Check all the connections outside of the pump. usually what it is with this one
Walbro wyl carb pops off, re-seats and holds at 2.5 psi?
Any suggestions.
You can try stretching the spring a little bit and test the pop off pressure. If it leaks off, the needle could be bad. If you replace the needle & gaskets and it still leaks down the needle seat is probably bad. You'can't replace the seat so if that's the problem the carb is scrap and you wasted your money on a rebuild kit. You can buy a new carb for the price of a Walbro rebuild kit so you're better off buying new carb if you can't get the needle to seat.
Keep making informative videos like this one
Do you still use that to test carbs ????
Plus Tard Mon Ami ~!~!
Great video it really helped me out
does anybody know what the symptom would be if a 2 stroke carb is failing the return outlet pressure test?
I have mityvac 8000 that only does vacuum not pressure. Can I do these tests with vacuum only rather than pressure?
The problem with vacuum testing these parts is that you're pulling the parts together on the gaskets making a better seal. A pressure test would push against the needle and gaskets allowing for a truer test.
Thank you 4 the good info I just got 1 of thoes mini vac
Great information thankyou
yall ever thought about buying a 10.00 manual pump blood pressure cuff and just pulling the hose off the cuff sticking it to the carb? lol after your done you can also check your blood pressure
Have you tried it
I have had carburetors hold pressure but not vacuum know the carb was bad
Nice job👍👍👍
Awesome testing. TU
excellent video!
Great video
Superb
great idea!
Thanks!!!
Top
Never checked the tool for leaks first!
Interesting
bom . vou comprar...
it's a great tool!
doublewide6 já vi que dá prá usar na reparação de roçadeiras e motosseras e motos também.foi uma luz em alguns defeitos de difícil diagnóstico. só estou aguardando a visita do representante.
you should be checking for fuel tank leaks and vent trouble with that tool.
thanks, just ordered a mv8500 for testing leak down on a snowmobile rebuild. Good to see this as I have a couple carbs on some saws to go through as well.
any idea what the differences are between models 8000 and 8500?
@@jbbolts not 100% sure but I think the 8000 will only draw a vac, while 8500 can both vac and pressurize?
@@MOAArtstore going through the auctions on ebay it looks like it comes down to the accessories... the 8000s are listed as vacuum pumps... and after all its in the brand name too