Motorcycle Repair: Occasional Cold starting problem, air fuel mixture, stock honda

Question
Bike - xr650l 1997 model
the bike is entirely stock HONDA.
country -  Guyana south america
odometer - 48000kms
recently changed Piston & rings -std again as recommended by mechanic + new air filter, new float valve    I have also used STP carb cleaner  in gas occasionally .
bike has been tuned to start without choke (mechanic insisted)
3 out of 8 consecutive cold starts the bike took more than 40 seconds grinding the starter to start. the other times the bike would start just as you touch the start button.
note that the three occasions were not consecutive.
there seems to be a lack of qualified mechanics available, so i'm seeking assistance on-line.

Thank you for your time.


Answer
Andrew, normally I only answer questions on older Hondas but it sounds like you need to find another opinion.  A bike needs a richer mixture to start cold. Normally, it needs an air fuel mixture around 10-12:1 for good cold starting.  If the engine has that rich of a mixture when hot, it won't start well hot and it may perform poorly.  An engine likes a mixture  of 15-17:1 to run best.  If you set the engine so rich it starts well cold without the choke, the bike is too rich when hot.  You need to set the carbs to the factory specs to get the best all around performance.  Those engineer spend a lot of time and resources to find the best compromise on fuel mixtures.  

Regards
Rich