Datsun Sunny bolt.
I'd managed after a bit of a guddle to get my Werniers under the dash so I knew what diameter the loose breather pipe was, and tracked down this bolt of the same diameter
Tonight when I went to remove the hose from the breather pipe, it came completely loose from the tank.

the excess of the bolt head cut off.

You'll like this:  How to get the bolt through the hole in the side of the filler tube without dropping it in the tank?
Feed it through some stiff wire, feed the wire through the hole in tank. you can get everything lined up. With enough excess wire sticking over the filler hole and enough sticking out the breather hole, you don't need to worry about it dropping and can simply pass the bolt through

I was so impressed with my own cleverness right up until the point when the bolt wouldn't go through the hole

The diameter of the pipe was slightly narrower where it goes through the hole than where I measured it


Back to the drawing board. I suspect I'll be lucky to find another bolt like that but a smaller diameter. Guess I'll need to pop down and see my friends at the bike club and see if I can get a hole drilled through a bolt in a lathe.

Applying the thinking hat and solving problems with work arounds is satissfying.

Hooray!
Worked out what's wrong!
I had dismissed the problem as being a choke problem after disconnecting the choke made no difference. But I was speaking to a local guy who explained that disconnecting it would make no difference and explained its workings. Sure enough, the spring must be bust. Turning the disc makes no difference to the valve on the carb. Need to order one from somewhere that won't take a couple of weeks to deliver.

Have you been out after wiring or setting the choke to be fully open at all times yet ?

As an ongoing test that would be a good thing to do, the choke is only
really needed to start up the engine from cold, so once the engine is warm things should
improve...

Peter 

Good point Peter. It's a bit late now. Neighbours have small kids. Don't want to wake them. Tomorrow morning I'll take it out for a quick spin minus airfilter tomorrow. I'll try and work out some way of holding the choke fully open. After all, it could be a red herring or only half the problem.

Wooden clothes peg?

I dont know what carb you have but it should be quite easy to keep it open, elastic bands, gaffa tape strip,
thin wire.... Anything really.

I would be interested to hear what happens 

Peter

Undo the threesmall screws and turn the heater element clockwise 1/4 turn then retighten the screws the choke will then stay open.

More playing. Silly me. I assumed the spring in the choke was broken, as turning the cover after loosening the 3 screws  made no difference. But
the choke flap was jammed shut due to the position the throttle lever arm bit was in on the a stepped cam plate on the other side of the carb. It moves freely now. (not sure what step it should be sat in and surely it can jump around a bit anyway)
I haven't taken it for a run yet because...
The tank breather tube can't be made from a smaller bolt, as putting a decent sized drill down it will leave it with an overly thin wall.  Therefore I'll go back to my original breather bolt that I concocted, but am widening the hole slightly in the neck of the tank with a needle file from the dashboard side (seriously tedious)so that it'll fit. To stop all those nasty metal filings making their way into the tank, I put a large dollop of grease round the hole which I think is collecting them pretty well (I couldn't find any magnets)
I hope to get this done tonight...late enough not to be able to try it without waking neighbours kids. 24 hour sunlight means you really have to keep an eye on the time!

Well. Managed to take it for a spin round the block. No aifilter. Choke open. Still banging and chugging away. I also removed and blew down  the vacuum tube to the distributor doesn't seem to have any leaks (I'll try again in a bucket of water later)

Take the vacum pipe off the carb a d with the distributor cap off a good suck will show you the base plate move and hold until you stop sucking.

Cheers snoop will check that out in the morning.

Vacuum distributor seems to be working. Gave it a good suck. tried blowing up the other end doesn't seem to be any blockages. Will recheck the points. I'm aware I'm putting off dismantling the carb, which is a likely candidate as the car has been sat a while, but it feels ignitiony. I'm suspicious of the coil as well, because it looks pretty beaten up.

If you have a hose from the filler neck to atmosphere you either need to take it uphill quite a way (I seem to remember Peter's goes up his screen surround) and/or fit a good valve that lets air but not liquid through. You can get them from rally dealers (I used Demon Tweeks) to stop fuel running out if you roll.

Otherwise you will get little expensive puddles, and therefore a potential fire, if you put a decent amount of fuel in

Doesnt help with the popping and banging though.  First thing is probably to check for air leaks in the exhaust, particularly if you have slip joints. A good HT silicone can solve it.

Well done on the MOT and enjoy
Dave

Well done Dave! Think I owe you a pint, and definitely my neighbour too. After rechecking ignition timing and setting the points, I took it for a spin. No change. My neighbour wandered across (harley owner/engineer and former beetle owner)and sprayed some carb cleaner on the point where the pipe from the carb enters the barrels: KABOOM!That might be the problem then . I stuffed a big wedge of silicone there and will take it for a quick spin tomorrow and see if it makes any difference.