Husqvarna 350 pressure test

[Bama Raised]

Today I was pressure testing a Husy 350 that I am in the process of rebuilding. I had an air leak around the spark plug that I was unable to stop without the use of an o-ring. My question is, is it normal not to be able to achieve an air tight seal simply by tightening the plug? This is only my second time performing a pressure test, and I don't recall running into this issue with the first saw I rebuilt. Thanks in advance.

 

[Ronie]

The plug should seal. I would try it with a different plug and if it seals, toss the old plug.

 

[redunshee]

The plug should seal. I'm curious where you are pressure testing from. I test from the plughole.

 

[Bama Raised]

The plug should seal. I'm curious where you are pressure testing from. I test from the plughole.

The impulse line.

 

[svk]

The plug should definitely seal, can you post a pic of the plug and the thread area of the cylinder?

 

[Bama Raised]

The plug should seal. I would try it with a different plug and if it seals, toss the old plug.

I was thinking that it should. It is a brand new NGK plug that came with the Hyway cylinder kit that I ordered. I'm afraid of cranking down on it much more than I already have. I will try a different plug and see if that makes any difference. Thank you!

 

[Bama Raised]

The plug should definitely seal, can you post a pic of the plug and the thread area of the cylinder?

I'll be sure to take some pics this evening if I can't solve the issue simply by trying a different plug. Thank you!

 

[svk]

I was thinking that it should. It is a brand new NGK plug that came with the Hyway cylinder kit that I ordered. I'm afraid of cranking down on it much more than I already have. I will try a different plug and see if that makes any difference. Thank you!

Take a good solid look at the threads and seat of the cylinder down before you crank it too tight. **** happens and it may be the cylinder if the plug looks legit.

 

[cuinrearview]

You have to compress the washer

 

[Bama Raised]

Take a good solid look at the threads and seat of the cylinder down before you crank it too tight. **** happens and it may be the cylinder if the plug looks legit.

I tried a different plug with the same results. Both were torqued to 15 nm as the service manual suggested. Technically it passes the pressure test according to the book, but this is bugging me. Video and pics below.

 

[Bama Raised]

Here are a few pics I took of the threads. I had taken a video as well of the pressure test but I can't get it to upload. When pressurized to 12 psi it slowly leaks down but it still over 11 psi at around 45 seconds.

 

[Huskitoter]

Is that one of their seconds off ebay?

 

[Bama Raised]

Is that one of their seconds off ebay?

Ordered straight off of hlsproparts.com

 

[Bama Raised]

Here is a link to the short clip that I tried to post earlier.

 

[PV Hiker]

Look at the head where the gasket seals. It is not even wear around the circle. Try using Emery cloth and smooth it out to create a better mating surface for the plug gasket. May not have been casted properly.

 

[svk]

You might want to talk to HLS before you do anything else.

 

[TheTone]

You say it was ok with an o-ring, so the plug or cylinder base is the culprit, and since it does it with another plug as well, cylinder base is most likely. Does the plug sit perpendicular to the base? Does it point slightly off center? Could have been drilled at a slightly off angle. If smoothing the base doesn't help, try a copper washer; this will seal better.

 

[Bama Raised]

You might want to talk to HLS before you do anything else.

I think that's a good idea. I just sent them an email.

 

[Bama Raised]

You say it was ok with an o-ring, so the plug or cylinder base is the culprit, and since it does it with another plug as well, cylinder base is most likely. Does the plug sit perpendicular to the base? Does it point slightly off center? Could have been drilled at a slightly off angle. If smoothing the base doesn't help, try a copper washer; this will seal better.

I may end up trying that depending on what HLS says, thank you!

 

[Bama Raised]

Look at the head where the gasket seals. It is not even wear around the circle. Try using Emery cloth and smooth it out to create a better mating surface for the plug gasket. May not have been casted properly.

I didn't even notice that, good idea. Thank You!