86topend w/ 85bottomend

[lowk3y]

I have an 86 atc250r that's bored out but the motor case was broken around the shifter....so I switched the bottom end out with an 85atc250r...will thre be any differences by doing this? And which cdi should I use 85 or 86?

[bkm]

No difference at all. You use the cdi that matches your wiring harness.

[lowk3y]

Ok...i have both wiring harness is one better than the other and also I have carbs for both years which one would be best to use?

[shortline10]

The 86 harness will make it easier to find a CDI box when it goes bad ......

[bkm]

Ok...i have both wiring harness is one better than the other and also I have carbs for both years which one would be best to use?You'll notice no difference between the two CDI units. The 86 style is the same as the 86-89 trx so if it takes a dump, you have more choices to find a replacement. 85 was a one year only cdi.

I always preferred the 86 carb over the round slide 85. They're both 34mm.

[lowk3y]

Alright thanks....now im tryn to figure out which carb to go with and also what spockets to use(number of teeth) front and back ...

[lowk3y]

34mm ok I noticed that...so its more preference Than any thing with the carb?!
so what about jetting im in the mountains 3600ft should i start with a certain size