Hard to start

Hi all
my 1978 Z650 runs fine when out but the following day it is very hard to start and usually at least one spark plug needs to be changed as they are very sooty before it runs on all four cylinders, it has been strobe timed and runs perfectly apart from start issues, the only thing I have noticed is the points are the wrong way round, the left pair marked 1-4 is actually sparking 2-3 and likewise 2-3 are actually firing 1-4, would this make any difference, it is all standard ignition system and is a US import

The sooting and plug fouling when left overnight is very likely down to oil fouling due to leaking valve stem seals which allow oil to leak into the combustion chambers when stood overnight.
The next time the bike has been stood overnight remove the plugs before starting and i'll bet at least one will be wet with oil.
The points orientation is not an issue.




 

Before you fire it up in the morning, pull the plugs and smell them.

Does it smell like oil or gas?

Dry soot covererd plugs may indicate a very rich condition.

This will also allow you to check if your petcock is leaking gas into the cylinder whick could cause hydrolock if severe enough.

Which plugs are you using?

The choke pickup tubes, or passage in the float bowl, could be plugged, leading to hard cold start on the affected cylinders.  Also, valve clearances that are too tight also lead to hard start, particularly when hot.

I have tried NGK B8 and B7 ES and nippondenso W22-E U 

I am planning to remove the carbs soon for Vapour cleaning so will check the chokes and what size jets are in