vacuum/pressure testing a saw with no impulse line

super3 said:

make up a block off plate for the carb flange with a barb for the hose

Click to expand...

FATGUY said:

I was toying with the idea of taking the rings off the piston and going through the spark plug hole. Thank you gentlemen.

Click to expand...

super3 said:

make up a block off plate for the carb flange with a barb for the hose

Click to expand...

blsnelling said:

+1. Throw a piece of inner tube behind the muffler and tighten down. I use a piece of 1/4" plate steel though. I clamp a piece around the intake to seal it. You can put your nipple on either side.

Click to expand...

KMB said:

I use the impulse lines on my saws with a piece of rubber for the exhaust port and a piece of rubber for the intake held on by the carb. But I would like to use the plate steel method if I can get the steel and have the tools to make it up.

Here's what I figure I need to do. Once I find a source for the steel, have it cut to size (or use my hacksaw). Then buy the proper barb, and a tap and die set to thread the steel for the barb. Then use the carb mounting holes as a template to drill the holes in the steel (to attach to intake). Did I miss anything?

Kevin

Click to expand...

cjcocn said:

Buy your flat stock just wide enough to cover your exhaust port (1 1/2"?) to reduce the amount of grinding that you have to do.

If you plan on using it on more than one saw, consider putting a slot on one side so that the plate will fit different sizes of ports. Then you can cut different pieces of rubber - one for each saw - so that you can have holes in the rubber as opposed to slots. That should make it more airtight.

Click to expand...

cjcocn said:

If you plan on using it on more than one saw, consider putting a slot on one side so that the plate will fit different sizes of ports. Then you can cut different pieces of rubber - one for each saw - so that you can have holes in the rubber as opposed to slots. That should make it more airtight.

Click to expand...

super3 said:

make up a block off plate for the carb flange with a barb for the hose

Click to expand...

volks-man said:

i use inner tube and place it between the carb and the intake. the plate i made is for the exhaust. got one made up yet fatguy?
<a href="http://s263.photobucket.com/albums/ii150/volks-man/?action=view&current=PICT0830.jpg" target="_blank"><img src="http://i263.photobucket.com/albums/ii150/volks-man/PICT0830.jpg" border="0" alt="Photobucket"></a>

Click to expand...

FATGUY said:

LOL, No, work getting in the way of making stuff for me, can you believe it?!?!?

Click to expand...

pioneerguy600 said:

3/16-1/4" thick aluminum is easier to work with and does not rust, it can still be bored and tapped, made all my blockers from 3/16" and a piece of rubber gasket material for between. You don`t have to remove piston rings to do either vacuum or pressure test, piston rings don`t seal perfectly at any time in the lifespan of an engine and it does not matter where the piston position is in the bore while performing tests on a 2 stroke. I made my air connector for my vacuum gauge from an old sparkplug but I also have air hold fittings that screw in the sparkplug hole of all engines that the air chuck of an air line will connect to for doing low air pressure tests to find leaks.
Pioneerguy600

Click to expand...

pioneerguy600 said:

3/16-1/4" thick aluminum is easier to work with and does not rust, it can still be bored and tapped, made all my blockers from 3/16" and a piece of rubber gasket material for between. You don`t have to remove piston rings to do either vacuum or pressure test, piston rings don`t seal perfectly at any time in the lifespan of an engine and it does not matter where the piston position is in the bore while performing tests on a 2 stroke. I made my air connector for my vacuum gauge from an old sparkplug but I also have air hold fittings that screw in the sparkplug hole of all engines that the air chuck of an air line will connect to for doing low air pressure tests to find leaks.
Pioneerguy600

Click to expand...

stipes said:

Would goin tru the exhast port give a better reading if the piston was TDC??? And what would be better vacuum or pressure it with air and check for leak off...It is a area I really dont know alot about.....

Click to expand...

litefoot said:

I don't think the exhaust or the intake would make any difference. Leak off or leakdown is a totally different test for the upper cylinder to check ring seals. Pressure/vac testing, although it will pressure the upper cylinder is typically for testing the crank and case seals. Here's an example from the 044 service manual:

After blocking off the intake and exhaust, pressure up to 8.7 psi and verify the the saw holds this for at lest 20 seconds before dropping. To vacuum test, apply negative pressure (vacuum) to 5.8 psi and verify it doesn't drop more than 4.3 psi in 20 seconds.

Edit: You may need to plug your compression release to get a good vacuum test.

Click to expand...

bama said:

I just bought a brass fitting that is the same size as the spark plug and put the piston in BDC. I always test from the plug hole. I still block off the muffler and carb. It was an easy tester to make. Spent about $25 for vac and pressure. I use a blood pressure cuff(got it for free at the clinic). I can "suck" 8 pounds of vacuum with my face, so I cheat and don't use a vacuum device. I am a trumpet player, so it helps to have strong facial muscles.

Click to expand...