Rough idle question.

SODAK-DOO

Well-known member
Premium Member
Dec 3, 2015
189
53
28
eastern south dakota
I have a 2018 850 summit sp 154 3" with 250 miles. issue i had all winter is a very rough idle that would jump around from 900-1300, but ran great when riding. spark plugs index were good, and new plugs and indexing did not change anything.

also have the same sled in a 2017 and that idles smooth from 1150-1200 all the time.

All until yesterday. While getting them ready for summer, i siphoned the fuel out and replaced with a 50/50 mix of premium/av gas 110ll and then the rough idle was gone and idles from 1150-1250.

Ran premium all winter.

thoughts from anyone that have dealt with anything like this?
 
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