Compression for the Husqvarna 350 Domed Piston?

[dsell]

Are you pulling the rope until it stops climbing? Do you have other saws to test the gauge on?

Yes, I just did that, the gauge is good.

 

[3000 FPS]

Update, I had two 350's in the shop with dished pistons. I didn't test this one prior to tear down. It's back together now and runs like a champ. Cold pressure, 100 lbs., tested it 3 times. This piston and cylinder looked better than the one I posted pictures of that blew 110. I bet this one will increase after a few tanks. I've never had a saw that starts as easy. I'm surprised, most saws with 100 lbs you could pull on them all day long without a pop.

I just went out and confirmed my gauge. I recently bought a 55 and the owner showed a picture with a gauge connected at 135. I tested the 55 twice and it blew 135 each time.

Wow I just cannot believe they produced a saw with only a 100 PSI. I guess it is what it is. I just worked over my poulan 3800 because the compression was only 125 PSI. After some tinkering it now 150 PSI. That is more like it.

 

[nmurph]

Have you checked the decomp for leaks?

 

[3000 FPS]

Have you checked the decomp for leaks?

What these saws came with a decomp when they supposedly have that low of compression. Something smells fishy.

 

[nmurph]

What these saws came with a decomp when they supposedly have that low of compression. Something smells fishy.

Yes, the do (did). See the tiny hole at the top of the cylinder?

 

[3000 FPS]

Yes, the do (did). See the tiny hole at the top of the cylinder?

I just do not get it. If you make a saw that only has the compression of 100 to 110 PSI and that is suppose to be normal why would you need a decomp. Even a girly man could drop start a saw with that kind of compression with out the decomp. I see the hole and I believe you but just saying.

 

[dsell]

Have you checked the decomp for leaks?

Yes. I tried several times to clean up the original decomp valve and could not get it to seal. I pulled the decomp valve from the pictured cylinder, and it worked great. The crankcase was pumped with 10 psi and I sprayed soapy water over every nook and cranny.

 

[dsell]

What these saws came with a decomp when they supposedly have that low of compression. Something smells fishy.

I thought of this too. This is the 353 cylinder, right? They probably didn't want to redesign it for the 350. The 353 has the 45mm flat top piston with higher compression.

 

[nmurph]

Yes. I tried several times to clean up the original decomp valve and could not get it to seal. I pulled the decomp valve from the pictured cylinder, and it worked great. The crankcase was pumped with 10 psi and I sprayed soapy water over every nook and cranny.

I'm not sure what you mean? If the piston was above the transfers, pressurizing the crankcase would not test the decomp. Spray it with soapy water and pull it over to look for bubbles.

 

[dsell]

I'm not sure what you mean? If the piston was above the transfers, pressurizing the crankcase would not test the decomp. Spray it with soapy water and pull it over to look for bubbles.

I'm not sure where the piston was, but I didn't move the piston from the test where the one wouldn't stop leaking. The first one leaked like a sieve. I sealed the muffler off, put the sparkplug in, and placed a plate over the intake mount. I applied pressure through the intake and have a gauge adapted to the exhaust cover. Are you going to tell me that the piston/ring has zero blow by? I don't believe that for a second.