I was expecting this post to read that the oil finally turned up and that the car started great, the mixture was spot on and and it drove like stink... however that didn't quite happen.
The oil did turn up but I struggled to get the car to start even with the hand throttle. When it did start the AFR readings were as previous, but the car didn't seem very happy.
I started to think I had introduced a fault somewhere, and concluded that I must have introduced an air leak with the re installation of the cold start valve o-ring. So I decided to remove it again. Whilst it was off I decided to check it was working. When first installed I remember manually energising it and it all worked fine, but I don't ever recalling testing it in situ with the cars electrics. Sure enough it didn't work in situ. After much head scratching it turned out that the two connections to the thermo-time switch were reversed. All the text I had read had said that you couldn't get it the wrong way around as the terminals on the switch are different sizes. However my wiring loom has the same size spade connector for both the thermo-time switch heater element and switch hence the mistake. So in effect if I pulled the hand throttle level then from cold I was shorting out the starter solenoid to ground. Might explain the few instances were the starter didn't always engage correctly.
Its good to find faults like this, even if it has taken a while to realise.
Sadly the cold start valve wiring discrepancy didn't explain why the car ran so poorly and lean.
Whilst the throttle body was off to access the cold start valve, I once again checked the body and found it occasionally binding a little.
Suspecting the TAV, I decided to disassemble it all again!
This time I stripped it down further than last time, took a brave pill and pulled the piston out!
I cleaned out the piston housing, piston and ball bearing, where the old grease was pretty solid, and regreased with silicon grease.
I also noticed that the cam had a bit of a wear dip at one point which might have been giving a bit resistance. To fix the cam I swapped it for the one from my other unit that had no wear, and put it all back together.
With it all reinstated it was time to try again.
The engine burst into life first time but was now running very rich ( AFR = 10! ). The CIS mixture adjustment screw now needed a large adjustment to put the mixture back into the correct ballpark. I had to replace the plugs again as they had carbon fouled very quickly ( the smoke from the exhaust was very black and rich ).
After new plugs and resetting the idle I now had an idle AFR mixture of 14.7 and a CO figure of 1.5%. 1.5% is the bottom limit of the book spec so just in spec.
Interestingly now the static RPM tests show the AFR to decrease from idle with high RPMs showing sub 13 figures - sounds more promising.
I also experimented with the Innovate Exhaust Probe, and found that restricting the exhaust with a drinks can helped improve the idle values.
Not confident the exhaust probe would survive a drive, we took it for a test drive without the AFR gauge to see how it felt.
Well it felt - totally brilliant! Smooth pickup, zero hesitation at any revs and the hesitation in the 2-3K band totally gone and the valve train is so much quieter.
So in summary, not sure whether it was just the valve train adjustments or whether I have fixed an air leak around the cold start valve, but the engine is very much transformed. I thought it drove pretty well before - but clearly it didn't but it seems to now.
In celebration we took it for a long drive around the Hampshire countryside - a wonderful drive!
Now I could tinker further to see if I can improve on things - but I think for the moment I will leave well alone and enjoy!