Chainsaw Repair

You need to check the squish too tight is bad news detonation, etc.  44mm I'd suggest .020 no less than .018 squish.  Rule of thumb on widening ports for work saw is bore x .65 yours is 44mm x .65=28.6 29 should be fine.  The casting on the floor of ex port is anti reversion ridge.  Porters are actually cutting them in on some saws.  I've seen that ridge in Partners, Jonsered, and Husky.  Having said that I'd leave it.  87 is OK.  Most of us run premium non-e (if available) @ 32:1 w/synthetic mix oil.
Shep