I just purchaed an 89 LT250r from someone who rides at the 1000-2000 foot elevation level. I will be riding it at the 4000-5000 foot level. I will also be adding a FMF gold pipe, and K&N filter with holes in the airbox lid. I know the quads jetting will need changing, but I am not real familiar with this process. Does anyone have any ideas on what Main to start with, what position the clip should be in, and how many turns the screw should be set at. Will the pilot need adjusting? Any starting advice would be very helpful. Also, if anyone would explain the simplest way to undergo this process that would be great.

Thanks,

 

Are you using the stock 34mm Mikuni Carb ?

Are you installing the FMF muffler to match the pipe ?

Biff the airbox lid, even with vents it still wants more air.

Assuming 34mm Mikuni check what IDLE jet (pilot) is fitted, should be a #30, get a #27.5 also.

Mains, go to a #300 and work your way down, I ran a 300 at sea level with a similar setup to what you are decribing, at altitude you will need to be leaner (lower air density) guestimate that around a #280 will be where you finish up.

I found that with the FMF pipe / muff and opened up airbox that the stock carb went very rich at idle / low speed, even with a #27.5 we had problems with idle - 1/4 throttle load up.

If you can afford it buy a 38mm PJ Keihen, the performance gain is nothing short of exceptional on the LT engines.

Kiwi