Finally got engine running on bike carbs, tick over ok but very hesitant on acceleration.

Just done compression test with following results.

No 1 115 psi
No 2 125 psi
No 3 90 psi
No 4 125 psi

I know these are down on Haynes manual, that states 159 psi, any help would be appreciated

Did you have the throttle fully open? Might be worth checking the valve clearances as too tight may cause problems. If the compressions are still low the try a few squirts of oil down the plug holes then repeat test, if compression rises by more than 10% then it points to ring or bore wear. As to whether it's worth doing anything ? Carb in balance may? have an effect as well.

I ran engine for 10 mins to get to temp then did test mate. Will admit bit of novice with mechanics, have picked up knowledge from the build. I guess we're looking at an engine rebuild

I wouldn't bother rebuilding a 1.8 go straight for a 2.0L with injection head
You'll have 20+ bhp more and a lot more tuning optons