It will have to be apart and bore measured as several bore sizes have been seen on egines rated at 10/1 or 20/2.  Most likely 120mm but I have seen 114mm and 127mm.

 My experience with PH1 engines is somewhat limited but some of them, maybe all?  have a stub shaft on both the crankshaft and on the camshaft. You crank them from the camshaft to double your cranking speed.  As was said if your are barely getting enough speed to get it over center when you decompress it then it will kick back, even when everything's right. If the pump to too far advanced it will also kick back. The crank action required to start one is best discribed as brisk, casual cranking isn't going to cut it. Checking the pump timing will require either a manual or someone more knowledgeable than I to tell you how to do it.

Follwing up on an engine that others have diddled with is always an adventure.. Has the engine been run long enough to get all the air out of the system? White smoke is unignited fuel , not too much fuel, that would be black. I can't help you with the specs but if the engine had been sitting a long while my money would be on stuck pintles in the injectors. Lacking an injector tester it's  easy enough to check by swapping 1 and 2 for 3 and 4.  If the problem moves then its the injectors, if not then it could be any of several other things. Another easy check is if the smoke clears up a bit and changes blue when the engine warms up but the exhaust smells putrid and makes your eyes water then you have stuck or leaking injectors. Bottle cures can help stuck injectors if not severely stuck.

https://youtu.be/IU6rySjstsE
^^^This one should be clickable^^^
Good work Ken, very few of these engines see that kind of hours

I have Gibb keys in stock. No, you cannot reach the piston through the injector hole on an indirect injection Lister . Some of the clones are direct injected and can be.
 Flywheel in the way? Yes. Is it an issue? No. Use the other one and leave the #1 side off   
To find top dead center you first need a pointer and a refferance. Mount the #2 flywheel and lightly secure with a key. Next using a piece of heavy wire, or flat stock make a pointer on one end. You attach it to any handy bolt.  Point it at the flywheel rim, the closer without touching the better. Next you need to decompress the #2 cylinder. This can be done by loosening the injector. Next turn the crankshaft so the keyways are at 3 or 9 o'clock makes no differance which way.  Now on the number one cylinder you need to block the exhaust valve open as shown in the attached picture, not just a little bit open but as far as you can. Use a vise grip on the rocker to pull it open. Next carefully turn the engine until the piston hits the exhaust valve. Put a mark on the flywheel at the pointer. Next turn the engine the other way until it hits again. Place a mark under the pointer. Care fully measure between the two marks. Divide measurement by 2. and place a mark exactly halfway between. Cylider 1 is TDC when at the pointer is at your TDC mark.  Remove the block holding the valve open. Rotate the engine to your TDC mark.

Here are the flywheel marks on a 16/2 currently in my shop. Notice the 2? tvus means they are used for the #2 cylinder. Not all flywheels will have the #2 marks, just #1. If your flywheels are unmarked then you will have to find TDC and mark them

Ha!  The plot is already pretty thick at my end.  Last question first.  I read in the Lister manual that the shear pins were #6 taper pins.  I found them at McMaster-Carr and after three orders managed to get the right ones.  I had two to replace.  After hammering the pins tight I mushroomed both ends to look exactly like the ones that already there.There is no need to mushroom the taper pins
Boy, if I could time this engine without removing the idler gear or the cylinder that would make me a much happier camper.  I have a few questions.  When standing in front of the engine on the oil pump side, No. 1 is on the right?  I assumed the opposite.Correct
I did not tie up the lifters but they are still in there.  I wasn't worried because the manual says to use heavy grease to hold them up, and I assumed it wasn't difficult.  Before I do anything else I will secure them.
I wasn't aware that there is an existing TDC mark on the flywheel.  Powdermonkey suggested I would have to mark it myself.  Where on the flywheel would I look for this mark? I guess I'm a bit confused if you have a CS or a clone. All CS are marked, most clones are not. The marks are on the face of the rim. Sand it off and look for a line. This is TDC when straight up. About 4 inches from the line there will be a lightning bolt. It is always very faint and you must look hard to see it. This is the spill timig mark for injection. Remember the flywheels must be installed on the correct side of the engine AND with the correct side out.   .
I think I understand everything up until marking the cam gear.  It seems like you are saying the cam gear will mesh with the idler gear exactly the same before and after turning the engine to TDC.  How is that possible?  Also, don't know what this means, "Confirm by rotating back and looking again."I'm not sure to to put it any more clear than the first time, I didn't go to school for teaching, LOL. In order to put the engine in time without removing the gear you must find the correct position for the cam. Forget about the crankshaft at this stage its not material. In order to find the cam position it must be in the engine unless you want to spend a week building a jig? With the cam installed turn the crankshaft until the #1 cylinder lifters are in the position described before by me and Powder monkey. Forget about the crank position it makes no difference at this juncture Now that you have the cam in the correct position you must mark THE CAM GEAR it so it can be reinstalled when the crankshaft is in the correct position.  You can see the gear mesh to the idler on the RH side. Either mark one tooth or two, then take a picture with your phone of how those marks line up on the idler gear. Next pull the cam out far enough that its out of mesh with the idler. Next  move the crankshaft to TDC. Then install the camshaft so the marked teeth are meshing the idler same as before, NOT HE SAME IDLER TEETH but the marked cam gear teeth meshing the idler gear in the same manner as when you marked them. Finally check your work by rocking the engine back and forth near TDC while watching the lifters. Stop when they are correctly positioned and then look at your TDC mark. It should be at TDC
Thanks for the help - Dan

From today my fingers are busy drivng and towing our caravan for the next 7 - 8 weeks

Hope you have a great holiday, enjoy!