Pressure test using an air compressor

[Armosh]

Alright boys and girls. I need to pressure test my Husky 570 that I'm going to be putting the meteor big bore cylinder kit on and before I do I want to make sure the crank seals and what not are ok because this saw has seen some heavy use over the years. I got it from a tree service company and the cylinder has some heavy scoring and a compression test revealed about 108psi which is higher than I expected but obviously low. So short of buying a Mityvac 8500 vacuum/pressure test kit for 90 bucks, there must be a way to jerryrig my compressor to the saw using the Husqvarna pressure tester that goes in the spark plug hole. Only need about 10 or so psi as I understand it. Anyone have any suggestions? Thanks in advance.

 

[cookies]

check if your local autozone loan a tool program has a mightyvac or a different version of it. being rode hard and put up wet you might be better served cracking it open for new gaskets, seals and a good cleaning.

 

[Armosh]

check if your local autozone loan a tool program has a mightyvac or a different version of it. being rode hard and put up wet you might be better served cracking it open for new gaskets, seals and a good cleaning.

Yeah have been considering cracking it open. Not saying it looks abused perse, just looks like she's cut a few cords of wood in her lifetime lol. Doubt any of them have a tester like that to loan but I'll check. I feel like there has got to be a way to hook up my compressor to it though. Thanks for the input.

 

[SteveSr]

Yeah have been considering cracking it open. Not saying it looks abused perse, just looks like she's cut a few cords of wood in her lifetime lol. Doubt any of them have a tester like that to loan but I'll check. I feel like there has got to be a way to hook up my compressor to it though. Thanks for the input.

To do a proper leak test your setup needs to be stable and completely leak free... and be able to reliably measure 0-10psi.

About the only thing that a compressor is good for is to pressurize a saw/crankcase at around 5 psi so that you can dunk the saw in a bucket of water and search for bubbles.

 

[Modifiedmark]

To do a proper leak test your setup needs to be stable and completely leak free... and be able to reliably measure 0-10psi.

About the only thing that a compressor is good for is to pressurize a saw/crankcase at around 5 psi so that you can dunk the saw in a bucket of water and search for bubbles.

Absolutely right. The other problem with this is even it the saw will pass a pressure test, crank seals can fail under vacuum. So without doing both test your just fooling yourself.

Most times its just as easy to change out seals as it is to setup a pressure vac test.

 

[Modifiedmark]

Yeah have been considering cracking it open. Not saying it looks abused perse, just looks like she's cut a few cords of wood in her lifetime lol. Doubt any of them have a tester like that to loan but I'll check. I feel like there has got to be a way to hook up my compressor to it though. Thanks for the input.

You have the fitting to go to the spark plug hole? And you cannot figure out how to get that hooked up to a air hose? Really?

 

[Armosh]

You have the fitting to go to the spark plug hole? And you cannot figure out how to get that hooked up to a air hose? Really?

Yeah. Really. I'm probably over thinking it. Was thinking I need an inline check valve or something like it and a gauge in there. I'm new to this stuff and winging it. Might seem simple and straight forward for you but is new to me. But learning is half the fun.

 

[Armosh]

Absolutely right. The other problem with this is even it the saw will pass a pressure test, crank seals can fail under vacuum. So without doing both test your just fooling yourself.

Most times its just as easy to change out seals as it is to setup a pressure vac test.

I guess I'll just snag a Mityvac 8500 and call it a day. I'll probably be figuring out how to do the crank seals too.

 

[Yukon Stihl]

I have a regulator 0 to 150PSI that i put inline to my shop air to keep a constant pressure for testing.
Usually after the vacuum test fails the saw.

 

[Leeroy]

Used to be a saw guy here years ago that would take a drag off his Marlboro and exhale into saw.
I was young at the time and don't remember or know what he was checking.
Anyone else seen this done? He was well regarded and worked at a small but great saw shop that
catered to loggers. The type of shop that would take parts off a shelf saw if need be to keep you going.

 

[Modifiedmark]

Yeah. Really. I'm probably over thinking it. Was thinking I need an inline check valve or something like it and a gauge in there. I'm new to this stuff and winging it. Might seem simple and straight forward for you but is new to me. But learning is half the fun.

You have to have a regulator and gauge on your compressor, so just set the regulator to like 5-10 lbs..

 

[Okie]

If you are going to piddle with chainsaws and Automotive get a 8500 and get it over with.
I've got the equivalent to the 8500 (older model like maybe a 4500) that I've had for years.
I've got a large plastic tackle box dedicated just to the Mityvac, hose, hose adapters, brake bleeders.
I use a Briggs white in-line fuel filter in the hose when doing vac to trap any small particles THAT WILL get sucked INTO THE mityvac and hold open a check valve.
Mine is several years old and still going. I had to take it apart and carefully clean the check valves few times before I started using the in-line filter.
Really handy for bleeding brakes by yourself. Just keep a heads up and do not suck brake fluid into the unit.
Mityvac sells rebuild kits but I've never had to rebuild mine, but I take care of my tools and do not loan them out.

 

[Modifiedmark]

I guess I'll just snag a Mityvac 8500 and call it a day. I'll probably be figuring out how to do the crank seals too.

If your going to test a 570, make sure and plug it off with the manifold still on it to test it as well.

 

[Lightning Performance]

Yeah have been considering cracking it open. Not saying it looks abused perse, just looks like she's cut a few cords of wood in her lifetime lol. Doubt any of them have a tester like that to loan but I'll check. I feel like there has got to be a way to hook up my compressor to it though. Thanks for the input.

Don't crack it open if the bearings are clean and tight. Pull the seals and look. The seals are arguably worn out by now and PTO side is likely cooked and hardened. It's not worth the trouble they can cause. Flushing out the bearings and checking out a free rolling dry crank with tell it's own tale. Just do it right the first time. Many cheap out and smoke the tool.

Go rent the vac pressure kit that was suggested if your not equipped with a low pressure regulator. You still need the vacuum test more than the pressure. Vacuum leaks cause lean mixtures at WOT pressure leaks do not but they make a mess and raw fuel mix ends up in the clutch or coil area and right around the head. Seals are consumables around here on high hours anything.

 

[Armosh]

Good advice from you guys thanks. Just easier to buy the Mityvac 8500, can justify its use with other things as well.

 

[PV Hiker]

Since a chainsaw is always wanting to suck under vacuum, you want to start with the vacuum test for leaks. Using pressure first has a tendency to push the lips of the seals out, thus you might miss a vacuum leak that it may have had.

I've had leaks both ways, vacuum leak but no pressure leaks And no vacuum leak but leaks under pressure.

You are doing it right getting the combo Mityvac to both test. Look around your shop for available parts to cobble ways to attach, plug ports to close off access. Then save those items to find later.

 

[Armosh]

Since a chainsaw is always wanting to suck under vacuum, you want to start with the vacuum test for leaks. Using pressure first has a tendency to push the lips of the seals out, thus you might miss a vacuum leak that it may have had.

I've had leaks both ways, vacuum leak but no pressure leaks And no vacuum leak but leaks under pressure.

You are doing it right getting the combo Mityvac to both test. Look around your shop for available parts to cobble ways to attach, plug ports to close off access. Then save those items to find later.

I'm going to pick up some aluminum flat bar to cut and drill for an intake block off plate and use some inner tube to seal it off and the exhaust intake behind the muffler. Should work I think.

 

[Gord404]

well worth having your own, use mine a number of times a day and you will find it has a number of things you will use it for.

 

[Okie]

I'm going to pick up some aluminum flat bar to cut and drill for an intake block off plate and use some inner tube to seal it off and the exhaust intake behind the muffler. Should work I think.

Aluminum sign material works good.
Also steel sign material but aluminum more user friendly. sometime I have to double the aluminum thickness if it's the 1/8 inch thick type and also use flat washers on the bolts.

 

[heimannm]

I frequently just make a solid "gasket" from old buna rubber and put the carburetor and muffler back on.

Mark