You can normaly hear when a crank is on its way out on tick over, they tend to rumble. When the bike is riden on load the noise normaly lessens, its only off load it will really stand out.

If its the mains that are gone these can be got though the site, if its the big ends then really its a new crank job.

Try taking the gen cover off and rotating the crank by hand then pullin it up and down. There shouldnt be any movment at all. All the specs for the big ends are in the workshop part of the site.
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If I have to take the carbs off once more...