T540 XP MkI & MkII Compression Issues

[TheShopBend]

Hello I have two top handle 40cc husqvarna saws in the shop both suffering from low compression 95psi hot 103 cold. Threw a new cylinder and piston at the MkII and saw no change in its compression. Yes it was fresh and had not seated at all but still 103 on a fresh build is low or seems low to me for an autotune saw. The MkI we replaced a piston assy only and got slightly better results and went up to 110 psi but that's still low considering the spec for autotune saws is at least 130 psi. So with all that said I decided to take a BRAND NEW T540 XP MkII and tested compression which ended up being 106 psi. Is there anything that can be done to help these saws achieve more compression?

 

[Squareground3691]

Did you try checking ur squish band , with a piece of solder , see were it sits . Increase ur compression you’d have cut it down smaller, assuming, not sure what the stock numbers are for that saw ,

 

[srcarr52]

The adapters to the 10mm plug threads usually add chamber volume because they don’t have a check valve in them. So it causes false low readings.

 

[SCHallenger]

I wondered about that. I had a 562, 2013 model, which only registered 135 after being well broken in.

 

[TheShopBend]

The adapters to the 10mm plug threads usually add chamber volume because they don’t have a check valve in them. So it causes false low readings.

No need for the adapter i use a genuine husqy gauge with a 10mm end on it i have two one for cmr6h plugs and bpmr7a plug saws.

 

[TheShopBend]

I wondered about that. I had a 562, 2013 model, which only registered 135 after being well broken in.

135 is proper spec nothing wrong there

 

[TheShopBend]

Did you try checking ur squish band , with a piece of solder , see were it sits . Increase ur compression you’d have cut it down smaller, assuming, not sure what the stock numbers are for that saw ,

Can't adjust squish on a customers saw it needs to stay some what reliable and not get hot