Pressure/Vac Test Sealing?

[Brushswamper523]

Ok I have been utilizing what I have for pressure / vac tests. I was wondering if there is a cheap alternative for block off plate for exhausts and carbs. I mainly do Stihl chainsaws right now so I would like to start with those first.

Currently I am putting scrap rubber behind the exhaust and bolting the exhaust to that. On the carb side I am removing the carb and putting a plug with electrical tape around it into the intake to tighten it up and pluging into the impulse line to perform tests but I don't always get a good seal. I have to hold this pump that and so on. If anyone can point me in a little better direction it would help alot. Like is there kit with a bunch of them out there or something.

I am currently using a maddox pressure/va tester for good old harbor frieght. And it has found some good seal leaks so far but it was a mission trying to block everything off.
Thanks in advance

 

[Chevboy0167]

This place is across the pond, but at least you have some Stihl part numbers and some images. Don't think they will sell to homeowners tho.. The sealing plates start on page 5...

https://www.dlsmallplant.co.uk/special-tools/?sort=featured&page=5

 

[Homer6679]

I buy rubber sheets from Home Depot that are normally for plumbing and sheet metal. I work in hvac so it’s easy to come by. For the exhaust side, I trace the exhaust gasket out on the rubber sheet and cut it out and drill my holes. Then bolt up in this order: rubber gasket/exhaust gasket/muffler
For the intake side I trace a carb gasket on my rubber sheet and sheet metal. Cut and drill my holes then I bolt up like this: rubber gasket/sheet metal/carburetor.

 

[grizz55chev]

If you don't get a proper seal on the first try, apply a small film of axle grease to the sealing surface, works in a pinch.

 

[SteveSr]

I buy rubber sheets from Home Depot that are normally for plumbing and sheet metal. I work in hvac so it’s easy to come by. For the exhaust side, I trace the exhaust gasket out on the rubber sheet and cut it out and drill my holes. Then bolt up in this order: rubber gasket/exhaust gasket/muffler
For the intake side I trace a carb gasket on my rubber sheet and sheet metal. Cut and drill my holes then I bolt up like this: rubber gasket/sheet metal/carburetor.

You can also expand on this to add an aluminum backer plate. this way you don't have to bolt up the muffler and carb. You may need to add some aluminum bolt/stud spacers from your local hardware store.

These also work great for sealing the crankcase when you are cleaning/de-greasing it.

 

[Homer6679]

You can also expand on this to add an aluminum backer plate. this way you don't have to bolt up the muffler and carb. You may need to add some aluminum bolt/stud spacers from your local hardware store.

These also work great for sealing the crankcase when you are cleaning/de-greasing it.

How thick is your aluminum backer plate? I find that almost all the exhaust and carb mounting bolts are sleeved so therefore you would need a backer plate the thickness of the sleeve in order to apply even pressure to the gasket/block off plate. Seems more work to make something when you could just use the carb and muffler. I hadn't thought of using them to clean a crankcase, but they would work pretty good I imagine.

 

[AW1]

I also use 2mm rubber wedges to blank off both exhaust and inlet ports, am also fortunate to have all the Husqvarna blanking plates, all of which are available.

 

[president]

How thick is your aluminum backer plate? I find that almost all the exhaust and carb mounting bolts are sleeved so therefore you would need a backer plate the thickness of the sleeve in order to apply even pressure to the gasket/block off plate. Seems more work to make something when you could just use the carb and muffler. I hadn't thought of using them to clean a crankcase, but they would work pretty good I imagine.

Isaw the video that the chainsaw guy that removed the carb and pushed
the boot into the cylinder side, and used an av mount zip tied to the boot

 

[SteveSr]

How thick is your aluminum backer plate? I find that almost all the exhaust and carb mounting bolts are sleeved so therefore you would need a backer plate the thickness of the sleeve in order to apply even pressure to the gasket/block off plate. Seems more work to make something when you could just use the carb and muffler. I hadn't thought of using them to clean a crankcase, but they would work pretty good I imagine.

The backer plates are .062" aluminum. The photo below shows my current homemade block-off kit.

1 - carb manifold plate.
2- large & small muffler plates.
4 - large diameter spacers for gluing clam shells together.
1 - temporary decomp plug.
1 - bicycle inner tube for 1-off when other adapters don't fit
4 - misc nuts for short spacing.
12 - misc aluminum stud / bolt spacers.

 

[huskihl]

I’ve used the same 2 rubber wedges and the carb or muffler for almost every saw I’ve done. No need for specific bolt patterns for each individual model that way. Some strato saws need plugs for the fresh air ports but that’s about it.

 

[Brushswamper523]

Thanks everyone for the responses. I am going to attempt to make some I will let guys know how it goes

 

[WI_Hedgehog]

The muffler is holding a wedge in the front (thanks @huskihl) and D-I-Y in the back. Cheap, easy, and fast.

 

[huskihl]

View attachment 1162634
The muffler is holding a wedge in the front (thanks @huskihl) and D-I-Y in the back. Cheap, easy, and fast.

Gorilla tape and a hose clamp will work on a round boot style intake spigot as well

 

[Vintage Engine Repairs]

I recommend you only use a block off plate on the intake in place of the carb and no rubber between it and the boot / manifold. I have come across warped manifold faces and warped housings, both of which, rubber strips compensate for. You think you have a good seal, but when the carb is on, you don’t.

 

[Gord404]

testing just on pressure isn't good enough, have vac as well- find sometimes pressure is good but on vac just watch the needle drop- seals may hold one way but not the other

 

[WI_Hedgehog]

testing just on pressure isn't good enough, have vac as well- find sometimes pressure is good but on vac just watch the needle drop- seals may hold one way but not the other

Tested with 7.5 PSI (Freedom Units) pressure (to find any leaks) and 7.5 vacuum, both while rotating the crank with the decompression valve in (leaked) and out (no leaks). Cleaned up the decompression valve seat and then it didn't leak.

Learned it from you guys, thank you.

The carburetor boot is very flexible and o-rings in it are good, and the machined surfaces are flat so didn't check with the boot on but will on other saws, that's great advice, thank you.

 

[Vintage Engine Repairs]

Pull 15 inches of Mercury, if you pull 7.5 vacuum, that about 3 psi. Too low.

 

[huskihl]

Pull 15 inches of Mercury, if you pull 7.5 vacuum, that about 3 psi. Too low.

7 each way is enough to tell if there’s any sort of leak that’s going to hurt a saw. If it’s got a leak that’s worthy of fixing, you’ll see the needle move at 7

 

[huskihl]

Tested with 7.5 PSI (Freedom Units) pressure (to find any leaks) and 7.5 vacuum, both while rotating the crank with the decompression valve in (leaked) and out (no leaks). Cleaned up the decompression valve seat and then it didn't leak.

Learned it from you guys, thank you.

The carburetor boot is very flexible and o-rings in it are good, and the machined surfaces are flat so didn't check with the boot on but will on other saws, that's great advice, thank you.

Decomps will almost always leak at 7 inches of vacuum. Usually pulling out on them slightly will seal it off.

 

[Gord404]

Pull 15 inches of Mercury, if you pull 7.5 vacuum, that about 3 psi. Too low.

Ya I don't know why they did that on the MV 8500, was not aware of that till I read a post on this site, probably yours