OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Quantum XTL 45 Cat - Hard to start and shakey

Good morning all.
Have a Husqvarna mulch mower with a Briggs and Stratton XTL 45 model 127802 Type 1539-81 code 99122359 motor that will only start using aerostart intervention and will cut out if the air cleaner box is closed unless the engine is revved up. It also shakes slightly when running, which I thought replacing the sheer pin on the flywheel would have fixed due to timing alignment.
This mower/motor combination has no throttle or choke cables using only the governor from the rear of the motor. (Photos attached)
The carburettor is the Primer version and has no mixture screw adjustments at all. (Photos attached)
So far, I have replaced the o-ring at rear of carbie intake tube, new gasket on air cleaner box, cleaned internal of carbie of varnish and grime, replaced flywheel sheer pin (half sheered), checked intake tube gasket at motor and tightened, cleaned rust from magneto and coil, replaced spark plug and installed a new air filter.
Attempted to complete the compression test, which was only 35 psi, but believe this model runs some form of decompression, which makes it difficult to test but easier to start. If it doesn't have this, then my problem is obviously compression and new rings would be in order.
If it is compression, I believe these engines are not very well suited to having new rings installed or being honed for O/S rings and pistons (plus cost of doing so), but I could easily be wrong/mislead.
Have removed the carbie again and taken photos for reference purposes to attach here and will give it another clean. Appears I missed a small jet on the left hand side front of carbie intake (near air box) that looks like it is covered in stale fuel varnish.
Have also played with the governor spring to get full throttle, which appears may have bypassed the mowers ability to use it's auto-choke.
There was a lot of oily grime around both the top and bottom of the engine indicating possible seals blown, which could have been caused by the flywheel sheer pin throwing out timing. Neither have been replaced at this stage due to trying to determine cause of hard starting and running rough.
Couldn't find any information on the XTL 45 using searches on this forum site, so thought it may help others if I can find my cure.
Thank you for your assistance.
Regards
Daryl