Greetings Cameron,
I might just address a few of your points that haven't been covered so far.
Am I correct on where they should go? Is there any reason why someone would connect the air hose as it currently is on the carby? If I am going to be testing the carby, should I be reconnecting the top hose to the cover and blocking off the bottom connection that should go to the decompression valve? From what I have read so far, my understanding is that if the connection is not made between the carby (above the diaphragm), and the cover, then there will not be sufficient vacuum above the diaphragm and the mower will rev high, is that correct?
This mower has a steel deck, which makes it less desirable for a resto than an alloy deck one. That said, it will be OK if metal cancer [rust] has not already got a grip on it, and it is maintained correctly - including washing down the deck underside after every use. Full crank engine is good.
As far as the way the hose has been hooked up - that's what's classed as a 'previous tenant 'improvement''. The which passeth all understanding, on the part of those who understand how the things actually work!
There are other indications of a 'clueless tenant' having worked on this machine, such as the wire around the muffler retainer clips, and the cable tie around the carby.
As I said initially I may have some really dumb questions, so I apologise if they were. My theory is best to ask, rather than just stumble in, after all this is predominantly about me trying to learn a bit.
+1 to Blumbly on this. You do 'know that you don't know', which is the best starting point!
I am unsure about the decompression valve, I don't think the one on my other victa would fit (I don't think it has enough reach), am I going to struggle to find one that fits?
No problem; this is the 'long type' Victa deco valve. While NLA from Victa, Oz-made aftermarket units are available, but not for much longer - the wholesaler has discontinued them, but there is still runout stock around. Around $35 new though. Google 'Victa EN72135' to find them.
In any case, the aftermarket units are superior from the serviceability standpoint, as they can be dismantled for cleaning/rebuild [and rebuild kits are available for around $5]. As the early Victa OEM units were, but not the later ones.
If I understand the way the governor works, the speed of the motor and hence the spinning of the flywheel causes a minor vacuum between the diaphragm cap and the diaphragm as the fins suck air through the tube. Based on this, if I was to check the integrity of the diaphragm, put it back together and blow into the tube, would I be able to get an idea of if the cap is leaking (if I understand this top section above the diaphragm correctly, it is effectively a sealed unit, and air should not escape)?
Yep, you've got it on the operating principle.
But it will be necessary to suck on the tube to check the 'airtightness' of the chamber, not blow. It's not possible to check on a slow leak by blowing by mouth, really. But it's easy to check if a partial vacuum is maintained OK, by sucking, and then sealing off the end of the tube with your tongue. It will soon be apparent if there's a leak.
Have some mouthwash or such handy though, to get rid of the nasty taste of petrol if there's a bad leak...
