Compression tester contact with cylinder top?

[Keithandstef]

Strange clanking noise when I use the compression tester on my Husqvarna 257. Almost sounds and feels like the tester valve insert is making contact with the piston head top. Clank, clank, clank as I pull it over. Needless to say I stopped immediately. Doesn't look like it's any further inside than the spark plug would be. Anyone else ever experience this?

 

[lone wolf]

Strange clanking noise when I use the compression tester on my Husqvarna 257. Almost sounds and feels like the tester valve insert is making contact with the piston head top. Clank, clank, clank as I pull it over. Needless to say I stopped immediately. Doesn't look like it's any further inside than the spark plug would be. Anyone else ever experience this?

Compare or measure it to the spark plug depth.

 

[Keithandstef]

The ends look identical in depth to me.

 

[lone wolf]

The ends look identical in depth to me.

Then it should not hit.

 

[PV Hiker]

Measure to confirm. What does the tip look like when you remover it? shinny from making contact?. If it don't do it with the sparkplug installed, not doing it with nothing installed, but doing it with compression tester installed, then I would expect it is the depth of the gauge is a little longer.

 

[Vintage Engine Repairs]

I had a similar issue, Is the saw all together or is this half way through a rebuild?

 

[Yukon Stihl]

Why are you testing compression?
A running issue?
could you have a bad rod bearing causing a running issue?
a bad rod could be the clanking sounds

 

[farmguywithasaw]

Why are you testing compression?
A running issue?
could you have a bad rod bearing causing a running issue?
a bad rod could be the clanking sounds

Have a 262 that had a bad big end bearings could definitely be the source of the noise

 

[Yukon Stihl]

i have a 359G here with the big end issue
piston and cylinder are reusable but a new piston is on order.At one time someone stuck a --- into the exhaust port as a stop.

 

[Keithandstef]

I was mid renovation of an old 257 that I picked up. I’m basically to the point where I don’t know what’s causing the clank noise when compression testing, but I don’t trust the tester. It certainly doesn’t make the noise any other time. The compression feels good so that good enough for me I guess.