When does it blow?

Turning lights on main or high beam, ignition only, kill switch off, riding over a bump??

The inlet bottom cam shell seems to have been bent slightly as its pointing outward a bit where the shells meet by cam cap, have to zoom in to see it. More importantly the top idler mount bolt on the right is loose and not tightened down!!, you dont want this coming loose. For the points you can rub...

Check voltage with meter on starter relay terminal that goes to starter motor when you press start it should show around 12v if its not turning starter. If voltage goes down to very low volts starter may be stuck. Also do same test at starter motor terminal, if you get around 12v then starter is duf...

Good idea to solder and drill the ends but think you will still have isses with the size of holes you drilled being larger than the others. From all the expense on carbs you have had i would spend £5 more and get correct micro drill. 1015 may know size whos doing choke plungers for you. Scumbay have...

On the lower carb in photo with red circle on it looks like tip of float valve is pushed to the side but float tab, it should sit central and not flop about in valve float body but you will get new ones in kit anyway.

As bike was a import and bit of a mess it could have been left standing for many years with dirt and old evoprated fuel blocking jets and airways. Have you removed all the jets to check them and blown airways out with compressed air and checked they are the correct sizes. Are the air screws undernea...

Could the float bowl have a leak and not floating correctly or be heavier than others for some reason or poor seal on float bowl valve to body, damage on valve rubber end?

Good find the cct diag. It looks like there is a external resistor in the live feed to each coil so suggest you check these for condition and connection and voltage too. With ignitor unit already removed you should be able to ground negative wire from coil going to ignitor briefly and get a decent s...

Many thanks zed1015 thats really great news!!

Do 1.015L (not 1015cc) barrels fit z900 bottom?.
Cam chain tensioner looks same fitting but not sure about height of barrels.
Crancase has already been enlarged for large liners when fitted RC 1170 pistons with bigger liners many years ago but were knicked.

You cold use liquid metal like epoxy resin thats supposed to be petrol proof and there is also some repair putty for petrol tanks on scumbay plus others, could build up quite a thick layer/blob around post, wont look too good though should do the job. I would glue it with float bowl rod fitted to ma...

Also touch probes together when changing resistance ranges to make sure meter reads zero before measuring

Yes thats 1.1 and 1.4 milion ohms which is very high compared to what it should be. Make sure fingers are not touching probes as moist fingers can cause readings to show when on high resistance ranges.

I take it there is no spark!

Might just need torquing down after being run for a while. Try torquing them all in correct order couple of times.
Not sure if you can add couple more lbs of torqure if that dont work though others on here am sure can advise on that.

To check for correct coil spark place no4 spark plug loose on cylinder head and with ignition on gently open 1&4 points with finger or tool. If points are open just short them with screwdriver or bit of wire for spark. To check fuel tap (asume you tried reserve and main) fit length of hose to ta...