I HAVE A 86 250R IT HAD A145 MAIN JET IN IT WHEN I GOT IT USED THAT SOUNDS A LITTLE SMALL IT HAS A COOL HEAD 21CC CR250 HEAD GASKET A CT RACING PIPE A STOCK JUG ON ITR FOR NOW GOOD ONE BEING BUILT AND IT HAS AN AFTER MARKET ALUMINUM AIR BOX ON IT WITH A K&N FILTER WHAT JETS SHOULD I START WITH ANY SUGGESTIONS I WAS THINKING LIKE A 170 0R A 165 SOMETHING AROUND THERE ANY SUGGESTIONS.PLEASE HELP I HAVENT HAD A CHANCE TO DO A PLUG CHECK HOPEFULLY THIS WEEKEND I WILL GET TOO BUT I NEED TO KNOW WHERE TO START THAT WONT BLOW IT UP BEFORE I CAN CHECK THE PLUG.

 

For safety, start with a .160. Then do your plug check.
Something to keep in mind; it may run really strong and be very lean, which is why plug checks are so important.

 

Check your plugs before you go off changing jets, I have the same situation, I am at sea level and I'm running a 135 min, I can't understand it but it works and rides hard.

 

Jetting is affected by more than elevation; ambient air temperature and humidity can also affect it and your fuel/oil mix. You may find that in some places, you will need to re-jet during the day.
Also, if your engine doesn't run smoothly on bottom-end-partial throttle, it isn't the main jet. Most likely is the pilot jet for that.
If you really want to learn about/ get help for the 250R, check out

http://pub20.ezboard.com/bhondatrx250r