562 Compression

[Jed1124]

What’s the typical compression on a 562xp? Friend of mine has a 555 that was blowing 95-105 on two different gauges. No scoring. He put a new 562 jug and slug on and is getting the same reading. Decomp is deleted.
Here’s the rub. The saw is running great. He had the compression tested at the shop that did the auto tune reset and they came up with the same reading on the new jug and slug, 95-105 psi. A 372 sitting next to it blew 145psi.
What gives?

 

[cuinrearview]

You're losing compression stepping down to 10mm.

 

[Brent Nowell]

I took a reading on mine new with zero hours and I believe it was 140psi. Nothing to write home about, I have about 5 1/2 tanks through it now, I should take another reading

 

[Jed1124]

You're losing compression stepping down to 10mm.

Is there an adapter or something to use on the gauge to get a proper reading?

 

[cuinrearview]

Is there an adapter or something to use on the gauge to get a proper reading?

The valve should be in the end of the hose, but you need an adapter to fit those smaller spark plugs. The adapter has no valve, so you're adding more volume, kinda like increasing the squish area. It's not much, but in a small saw it makes (obviously) a big difference in readings. If you don't have an adapter with a valve right at the tip and the piston looks good and it runs good I wouldn't sweat it. I personally have never measured comp on one.

 

[old guy]

I've got a 10 m/m adapter with the valve in the end, from Specialty chainsaw tools, makers of the tiny tac.

 

[Jed1124]

Thanks guys!

 

[Brent Nowell]

The valve should be in the end of the hose, but you need an adapter to fit those smaller spark plugs. The adapter has no valve, so you're adding more volume, kinda like increasing the squish area. It's not much, but in a small saw it makes (obviously) a big difference in readings. If you don't have an adapter with a valve right at the tip and the piston looks good and it runs good I wouldn't sweat it. I personally have never measured comp on one.

I never thought of that, makes perfect sense now! My reader has a valve at the gauge, not the end of the hose...