After I had my bike Ivanised I found the bike more difficult to start at first. I now find the bike a bit more temperamental and may need a few goes to start.
nitrama i had a similar issue and it turned out to be one of the fuel inlet o rings... I'd changed them for new when I Ivanised, but had nicked one. That cylinder was running cold as it was overfuelling, and didn't fire until the bike hit 6k. I actually bought 50 of em as Mike gave me a heads up to sourcing them...if you want half a dozen so its summat else you can knock out of the equation, pm me your addy buddy, i'll post em out pronto (Gratis obvs as the young people say lol)
You can always buy new starter jets if necessary. However it would not be a huge issue if the starter jets were a little larger than Mikuni 42.5 size as they are not in use unless the choke is operated.Are they stainless steel jet cleaners? I usually use brass wire from a brass bristle brush as it will not harm the jets.Never a great fan of Carb Cleaner, much prefer Cellulose thinners, it can tarnish the jets if they are immersed for over a few hours, but certainly dissolves lacquer quicker than carb cleaner.
Ultrasonic baths are great if you can get hold / borrow one. Cleans out all the small chambers to remove varnish.