Husqvarna 350 pressure test

[MacAttack]

Before you try anything else, i may be wrong (definitely wouldn't be the first time) but those don't look like the correct spark plugs for that saw. Those plugs have compression washers for sealing on a flat mating surface, from the pictures your cylinder appears to have a tapered spark plug seat, which would require a tapered spark plug, without a washer (gasket) to seal correctly. You might want to look into this before you start sanding anything or trying to make those plugs seal.

Edit: not sure if my eyes are deceiving me, in some of the pics it looks like a tapered seat, in others kind of like a flat seat.

 

[727sunset]

The surface hasn't been machined, still a rough texture.

 

[MacAttack]

This one picture looks almost for sure like there was a tapered plug installed (which i believe is required) at one point, and then more recently the gasket plugs, you can see the proof (wear) marks in 2 different places. I bet it seals tight with a tapered plug.

 

[Huskybill]

It calls for a rcj7y plug. I’d pull the cylinder and put some lapping compound on the compression ring and lap it into the cylinder. Simi chrome polish is finer grit compound. Repeat till you get a fine seal on the cylinder.

 

[MacAttack]

It does indeed call for that plug with the compression ring, maybe some lapping compound would help.

 

[Huskybill]

Add lapping compound to the washer and turn it clockwise, then counter clockwise repeat till you get a good seal. Just go back and fourth turning it. Like doing valves the compound will go back to the center of the ring.

350 saw plug
https://www.partstree.com/parts/husqvarna-503235108/

Thought what sparkplug does the 350TB use.? The leaf blower seems to use a tapered washer?

https://www.partstree.com/parts/husqvarna-544260901/

I say lap it.

 

[Bama Raised]

This one picture looks almost for sure like there was a tapered plug installed (which i believe is required) at one point, and then more recently the gasket plugs, you can see the proof (wear) marks in 2 different places. I bet it seals tight with a tapered plug.

There is a taper outside of the sealing surface, but where the spark plug seals it is completely flat. That picture is deceiving, it had me questioning my sanity until I went and checked the saw. lol

 

[Bama Raised]

I was able to solve the issue by turning a dowel slightly larger than the washer on the plug, then gluing a piece of fine grit sandpaper to the flat end. After a few minutes of working the surface with that, it was good to go. Now the saw only loses 1 psi over a minute, which passes the pressure test by a good margin according to the service manual. I appreciate the tips fellas, definitely helped me a lot.

 

[Bama Raised]

Add lapping compound to the washer and turn it clockwise, then counter clockwise repeat till you get a good seal. Just go back and fourth turning it. Like doing valves the compound will go back to the center of the ring.

350 saw plug
https://www.partstree.com/parts/husqvarna-503235108/

Thought what sparkplug does the 350TB use.? The leaf blower seems to use a tapered washer?

https://www.partstree.com/parts/husqvarna-544260901/

I say lap it.

Good idea, if I ever encounter this issue again I will probably go this route.

 

[MacAttack]

Glad you got it fixed!

 

[Huskybill]

Glad it’s fixed we all learned something.

 

[Sepia]

This one picture looks almost for sure like there was a tapered plug installed (which i believe is required) at one point, and then more recently the gasket plugs, you can see the proof (wear) marks in 2 different places. I bet it seals tight with a tapered plug.

There is a bit of an optical illusion going on in that pic. I have a new 288xp cylinder here in my hand and it looks just like that pic. However, it definitely take a washer type plug. I think there is a shallow taper cut into the plug bore before the threads are cut.

Also in that pic, you can see where the sealing washer is only biting into one side of the sealing area around the plug. I would guess the plug hole was not drilled/tapped perpendicular to the sealing surface.

 

[Sepia]

I there is a bit of an optical illusion going on in that pic. I have a new 288xp cylinder here in my hand and it looks just like that pic. However, it definitely take a washer type plug. I think there is a shallow taper cut into the plug bore before the threads are cut.

Also in that pic, you can see where the sealing washer is only biting into one side of the sealing area around the plug. I would guess the plug hole was not drilled/tapped perpendicular to the sealing surface.

I should have finished reading the thread before I wrote that post

 

[Huskybill]

I think the 350bt blower takes a tapered washer. Again think.