Essential Tool..

[stihltech]

If your time is all free, yes, make the block off plates. If you are in a shop trying to make money and not spend down time dollars, get the adapters.
Hardware store sell a plumbing rubber sheet in squares. I find this works very well for sealing and is durable.

 

[GMB74]

Using a blockoff plate and rubber gasket on the intake side works to test for leaks,
BUT
You are failing to test for one potential leak point, the spot where the carburetor mates to the intake manifold.
Unless you use the factory tool or a good replica of it (same size and shape as the carburetor), and no gasket other than whatever normally goes between the carb and manifold on the saw, you will not be able to identify all the potential air leaks.
The fat rubber gasket will seal better than the stock carb and manifold setup and you will not identify a leak at this junction.
That is the point of Tom's video.

I just fixed a saw that was running lean. It would pass a P/V test using a blockoff plate and rubber gasket, holding pressure all day long. Using the factory tool and only the standard gaskets revealed the leak point.

 

[PV Hiker]

You could go further down the rabbit hole thinking about this.

The gasket interface (soft seal) between the manifold and carburetor has been imprinted with the shape of both matting surfaces with clamping force. Over time that gasket can change shape and might not make the same seal as when it was new. Expansion, contraction and temperature can cause the seal not be be tight anymore.

How would you know for sure that your carburetor imprint is going to match the block off plate exactly as what the carb has imprinted into it?
See picture attached from Tom's video.

You might consider having a new gasket on hand that you can use instead of the old imprinted existing gasket to confirm any leaks in this location. After that you might as well just keep the new gasket to start a new seal bond.
.

 

[Vintage Engine Repairs]

If your are a Stihl freak- some rubber and a pair of scissors- hold the rubber in place with the carb and muffler supplied by the saw- test through the impulse hose.
There is no need to make it sound more complicated than it needs to be- simple tests can be performed by simple means.
Or you can buy shiny proprietary tooling- your choice- but neither is " essential" to get the job done.

Yeah using rubber is a great idea!

 

[Vintage Engine Repairs]

You could go further down the rabbit hole thinking about this.

The gasket interface (soft seal) between the manifold and carburetor has been imprinted with the shape of both matting surfaces with clamping force. Over time that gasket can change shape and might not make the same seal as when it was new. Expansion, contraction and temperature can cause the seal not be be tight anymore.

How would you know for sure that your carburetor imprint is going to match the block off plate exactly as what the carb has imprinted into it?
See picture attached from Tom's video.

You might consider having a new gasket on hand that you can use instead of the old imprinted existing gasket to confirm any leaks in this location. After that you might as well just keep the new gasket to start a new seal bond.
.
View attachment 1227613

Don’t worry that was to show the principle of the gasket in place. It’s off a totally different machine and that outline is from the manifold block which then has another gasket on the opposite end which the carb touches. The gasket the carb face actually touches will always be flat like the carb itself.

 

[Vintage Engine Repairs]

If your time is all free, yes, make the block off plates. If you are in a shop trying to make money and not spend down time dollars, get the adapters.
Hardware store sell a plumbing rubber sheet in squares. I find this works very well for sealing and is durable.

The whole point of the video - don’t use rubber and why…