Update
Swapping the coils and connections did NOT move the fault to the other cylinder, so it's not the coils, connections, HT leads or plugs. None of the wires from the engine speed sensor or the three white wires from the alternator have earth returns (it's a new stator). The battery charges from the three yellow wires from the stator. The computer still shows no faults.
I am forced to conclude that the fault is with either the engine speed sensor in the rear of the water pump area, or is a faulty spark unit. No spare unit is available. Is there a simple test to establish this, other than borrowing another spark unit?
If the engine speed sensor was at fault, wouldn't this affect both cylinders?
The injectors have now been professionally cleaned and this has made absolutely no difference at all. Right cylinder works fine but there is no idle on the left cylinder until the revs hit 2,000 or 2,100 and then the cylinder fires normally. No difference whether the engine is cold or warm. To recap:-
Swapped coils and associated wiring, no change. New coil and HT lead on the affected side.
Tested computer and spark unit in another Turbo, both ran perfectly. No errors on computer LEDs.
Plugs are sparking well and so are the spare plugs. Different plug caps made no difference.
New fuel filter and the petrol squirts out comprehensively from both the fuel feed and the fuel return pipe, if these are disconnected. No leaks when the engine is running.
I've been round the freshly powder coated frame with a flying earth lead, one end on the battery negative and touching everything I can find with the other end. No improvement.
If I wind up the idle speed to over 2,100 rpm the engine then picks up and climbs to 2,500. Very gradually decreasing the idle back down again works as expected and after a short while the engine slows and then goes onto one as it drops under 2,100 rpm.
I've looked at the routing of the various vacuum pipes and not found any of them crimped or impeded; also I've unplugged, clean and reconnected all the connections on the electrics plate behind the RH side panel and jiggled averything reachable to see if there's a loose connection, no improvement.
This bike is rapidly heading for the spares pile as I am running out of patience with it, the only saving grace is that it's worth more as dismantled spares than as a non runner.
Guys thanks for the various inputs.
Compression is good and equal on both sides. No 'conventional' air leaks - I've fitted new o-rings to the inlet tracts and the air feed. What I am thinking now is that some residual dust from the shot blasting (despite careful cleaning) has entered the left hand reed valve and jammed it open. At idle speeds, too much air gets in, but at 2,100+ rpm, the throttle butterflies are open enough for the engine to run normally. I'll take the unit off and examine / clean it, along with the piping.
The reed valve and air bypass units were not particularly dirty inside, and the reed valves were operating correctly; I dismantled and cleaned everything. But I did find that the thick short hose connecting the two mechanisms was badly cracked on the exterior. It was so well stuck to the units that in removing it, it was destroyed, but I can't see if the cracks had penetrated all the way through.
However I've obtained replacements pipes for the thick length and the two shorter connecting pieces which feed the inlet tracts, I'll fit these soon and try the engine again. I imagine that a crack in the thick pipe would affect both cylinders as it's common to both air feeds - but you never know.
Rob, I'll bet your bike comes good with replacement of the THREE hoses that route the air to that warm-up valve and to the respective inlet manifolds - it's a thing I've seen on about 6 turbos in Oz - cracked and leaking hoses. You might even think of removing that warm-up valve entirely - Oz bob's turbo starts and runs just like new, and it hasn't got the warm-up valve installed (I saw it hanging up in his garage the last time I visited him). Of course it might be necessary for you to have it in there - Bob's temperatures rarely fall below about 4 C.
I've dismantled and cleaned the warm-air unit, replaced all the hoses and clips, and this has made no difference at all. I can try running the engine with the twin feed hoses disconnected and closed off to the engine end.
So my feeling now is that the new stator is faulty. Does anyone have the readings that I should get via a multimeter for the stator connections? I am familiar with the regular CX stator readings, but not what the Turbo ones should give me.
Swapping the coils, injectors, plugs and cabling made no difference at all, the fault could not be made to swap sides. I would expect an injector fault to have made the misfire go to the other cylinder. The bloke who cleaned the injectors found no faults and fitted new internal tiny filters, afterwards showing me that both injectors were delivering equal amounts of fuel. This does confirm that the injectors themselves are working properly. I've wiggled every wire in sight to no avail!
I'll try the other ideas.
Re the stator cabling. The three usual yellow wires connect as per the regular CX - these do get as warm as the normally aspirated model - but there is a triple wire connecting up into the harness from the stator to the spark unit. I am assuming that this represents earth, left and right sides - unless it's like the regular CX high and low voltages, with some other connection, maybe an earth? Not exactly a white wire fix is it! I don't mind experimenting with a CDI bike but the though of blowing up a working spark unit or computer is not to be contemplated.
Thanks to all for advice, sadly all to no avail. The bike is now broken up as spares.
www.cx500.webhop.org/turbo
"I wonder how many of these bikes suffered such a fate due to the owner's inability to do their own repairs? "
You arrogant sod! Who the hell do you think you are? Where is YOUR CX home maintenance website ?? I can't seem to find it. Mine is the result of years of work and countless hours of development and is the primary internet resource for these bikes and for every message you have posted, I have had 1,000 visitors. So GEORGE IN INDIANA, can your mindless comments until you can produce something better yourself.