vacuum/pressure testing a saw with no impulse line

[FATGUY]

I've read a lot of great threads on this subjet but am still unclear as to how to do a vacuum and/or pressure test on a saw with NO impulse line?

 

[super3]

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

 

[blsnelling]

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

+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.

 

[FATGUY]

That's just crazy enough to work lol I like that idea, I was toying with the idea of taking the rings off the piston and going through the spark plug hole. Thank you gentlemen.

 

[blsnelling]

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

That would work too. I don't think you'd even have to remove the rings.

 

[KMB]

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

+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.

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

 

[cjcocn]

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

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.

 

[KMB]

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.

Thanks for the tips.

Kevin

 

[litefoot]

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.

I like the slotted side idea. You'd want to make the inside edge of the slot the width of the smallest diameter intake. Probably wouldn't be much of a "slot" as there's not a lot of difference between saws...I'm guessing.

Also, in my limited experience, rubber on metal (versus rubber on rubber) make a better seal. And the metal stock for the plate should have a nice smooth surface.

 

[volks-man]

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

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>

 

[FATGUY]

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>

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

 

[blsnelling]

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

Come on man. Get your priorities straight!!!!!!!!!!!

 

[stipes]

I'm kinda confused with this....

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.....

 

[pioneerguy600]

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

 

[KMB]

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

Care to share how you made the air connector from an old spark plug? Got pics?

Kevin

 

[stipes]

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

Thanks Jerry!!!

 

[litefoot]

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.....

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.

 

[stipes]

Thank you!!!

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.

That explanes more...I;m sorry I'm kinds dumb to this,,but when I start to have trouble with my MS440 I can check...It's gettin old,,and used the heck outta it...

 

[bama]

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.

 

[KMB]

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.

Sounds good to me. I'll have to give it a try.

Kevin