So, I have a 83 250r that I have had for about 15yrs. It has been at my dads for the last 10yrs. He maintained the bike serviced it and started it but never really rode it.

So, I brought it to Colorado from sea level and of course it needed jets. I pulled off the carb (a mikuni) and it had a 300 jet in it. I dropped it down to a 280 per the local shop and am going to take it out today to see how it runs.

My question is, what could be done to this bike that it could run a jet 3 times the size of stock. I think the guy I bought it from said it was bored but it has been 15yrs. I know the bike isnt stock it will eat up a stock banshee.

As for exhaust it has a DG pip and silencer. I dont think just a bore kit could cause such a jet increase I'm thinking it must have some head work or that it isnt even still a 250.

I know I'm asking alot but I cant stop thinking about what could have been done. The bike runs way to well to take it apart. Does anyone have any ideas?

 

THE STOCK CARB WAS A DIFFERENT BRAND SO THE NUMBERS ON THE JETS WERE DIFFERENT TOO,,, it would never run with a main 3 times bigger,,,

 

That makes since, I forgot about it being a different carb.
Good news. I got it running great Sunday. I replaced the 300jet with a 270jet and adjust the air mixture and it is running like a champ at 5000ft.

the 300 was used at sea level and I currently live in Denver CO