Carb testing

[countryhog]

trying to clean out my backlog. So far most of my carbs wont pass a pressure/vacuum test. It occurs to me i may be the problem.
What pressure should the pop off be?
How long should the carb hold sub-popoff pressure without falling to what level
How much cacuum should the carb hold and for how long
Me and my carbs thank you in advance

 

[Chainsaw Jim]

Pop off shouldn't be a problem unless the springs have been changed or messed with.
The main nozzle check valve should hold pressure without dropping. The carbon fiber check valves can be cleaned with carb cleaner and an air hose if there's a problem there. Not all carbs have check valves and those that don't will not hold pressure there.

 

[Lightning Performance]

trying to clean out my backlog. So far most of my carbs wont pass a pressure/vacuum test. It occurs to me i may be the problem.
What pressure should the pop off be?
How long should the carb hold sub-popoff pressure without falling to what level
How much cacuum should the carb hold and for how long
Me and my carbs thank you in advance

More info like Jim said. Some have, some don't. Model numbers is what these guys know. Find them on your carbs and list them.

 

[Simondo]

trying to clean out my backlog. So far most of my carbs wont pass a pressure/vacuum test. It occurs to me i may be the problem.
What pressure should the pop off be?
How long should the carb hold sub-popoff pressure without falling to what level
How much cacuum should the carb hold and for how long
Me and my carbs thank you in advance

This is my basic procedure with the carb off the saw and metering side open (mind your eyes against spray) .
Always do the pop off with a wet carb (the needle pocket )...wd 40 will do . With most carbs I like 12-15psi pop off to allow for tank pressure against the needle when the saw is not running. Pop off re seat should be close to the 12 psi or a little bellow .You want the pressure to hold and not slip on re seat. The carb should hold against the psi applied before pop off without losing any pressure really. Vac is something I don't use with most carbs as most of the things Im testing for are taken care of with the pressure test.
Don't get to carried away with the Psi by the way...pump up to 15psi max and if there is no pop off then stop..its passed popping off to low , just tap the needle leaver to check for re seat Psi.

 

[MustangMike]

I've had a couple of carbs recently that only held 8 PSI (both pressure + vac), but they seemed to work OK on the saw.

The did hold steady at 8.

 

[Terry Syd]

I prefer a fully vented tank, that way I can tune the pre-load on the spring the way I want it. Notice I said 'pre-load' - some may call it 'pop off', but that can vary as 'pop off' also depends on the size of the metering orifice. If one carb has twice the area in the metering orifice (bigger size hole), it will have half the 'pop off' of another carb.

It just depends on what you're trying to achieve. If you have a nice lean idle, you may want to have a very low pre-load on the metering spring to quickly get that fuel flowing when you crack the throttle. Conversely, if you have opened up the low speed circuit quite a bit, you may want to bring the fuel flow in a bit slower, so you go with more pre-load.

What works is just that, what works.

 

[Lightning Performance]

Both of those were way better than the gibberish that would be coming out of me. Between 5-15 is a good realm for things to happen in. Below that is not good. Alky is all different just like other fuels. Change the fuel type/mix you work on the carb. Most people just run pump gas. That what most carbs are built for. At least there is no barrel valve.

 

[Simondo]

I probably should mention due to the discussion including the "Modified " carb /Modified saw information , that my procedure deals with "Unmodified " common carbs and saws.