First, the jet installed in the replacement carby was the plain face jet. I swapped it for the ringed jet which is the one that's supposed to be installed.
So... I grabbed a new plug and tried it with the fuel off and then on... No go.
I removed the new plug and found it was wet so I pulled the pull-start mechanism at least 20 times (Exhausting!)... No go.
I tried with the fuel off at this point because I still saw what I thought was fuel coming out... No go.
I removed the fuel tank in case there may have been an issue with a leaky tap and the carburettor having an issue before moving forward further.
Removing the plug and finding it wet yet again, I tried the pull-start a few times with the plug out and noticed what appeared to be fuel coming out of the spark plug hole... even after that many tries with no fuel...
I removed the head and found a little fuel dripping down, and the cylinder appeared wet. I pulled the pull-start mechanism a few times and noticed what appeared to still be a lot of fuel coming out.
I removed the pull-start mechanism to check for fuel and on initial visual inspection found nothing.
I tipped the mower on its side and spun the engine a few times and quite a bit of fuel came out. I know it's supposed to lubricate the engine so I'm not sure exactly how much is supposed to be in there, but it seemed like more than there should be?
After emptying the fuel as much as I could and re-assembling the engine (Fuel supply still removed), I tried starting it with SYB. I got pops, and almost for a second it sounded like it was going to start veeeeerrry slowly... but it didn't.
I thought it could be because there was insufficient fuel, so I installed the fuel supply and tested again... No go.
I thought the scoring or compression may be an issue, so I tested again. With the decompressor on I got about 60 PSI and with the decompressor port blocked with the spark plug I got around 85-90 PSI (And trying to pull-start the mower was very difficult)
I removed the snorkel hose and sprayed some SYB down there as I pull started it (Not easy :-/)... I got a few pops, but no go.
Note, all of the above was done with the muffler removed. I recognise in hindsight that this may have been an error, as the pressure waves going back into the block from the exhaust may have been necessary.
At this point, I'm thinking 2 things which I haven't tested:
1 - Yes Norm, I agree, it could be a carby issue and if anything considering it's new and the assembly shouldn't be worn, I'm assuming it may have to do with the needle & seat along with the float valve, however, to get one of those awesome ones from the UK may take time. If they're that awesome I may get them in bulk as you did which would drop the price per unit down to around $2.50 but would still mean I need to spend $250 to get that value haha.
2 - The back-pressure which wasn't available due to the muffler not being installed was stopping the mower from firing.
I'm hoping to test further tomorrow, the muffler is the quick and easy test so I'll try that first, probably with the fuel supply disconnected and with a decent supply of SYB down the snokle and in the spark plug hole, and if that doesn't resolve it I'll take apart the new carby and check the needle & seat and see if I can find anything there.
