[farrell1001]

I am working on a 2006 440x with LC domes trail needles on the 2nd clip 210 mains and 25 pilots & The carbs do not have power jets. Based on the jetting forum most people with this setup should be running 300-320 MJ and this sled has 210.. the plugs seem quite rich actually but its hard to predict how it will run as it is in the mid 20's Celsius and humid. Any insight on why the 210 may be there? Also the previous owner had BR7 plugs in it

 

[PeterSmoreEater]

That seems really lean for having the power jets plugged. On my 06 440 im running, with the power jets plugged, 280-300 mains, 25 pilot. 1.5 turns on the air screw and the needle all the way down. Runs great for me. But you should go up to at least a 280 id say.

 

[PeterSmoreEater]

Oh and BR9ECS plugs but ive also heard of guys running the BR9EYA plugs too. BR7 plugs are too hot.

 

[farrell1001]

That’s what I figured! The carbs don’t have power jets at all so I assume they are pre 06 carbs. Sounds crazy lean but it seems to run half rich to be honest.. almost have to wait for some colder temps to get a true indication!

 

[6timechamp]

210 is what you would use for drag racing. It may seem rich now, but on a wide open pull at -5, they will need 280s like the previous post

 

[TheBearAk]

I agree, 7 is to hot. 9 is standard.

Not much difference between BR9ECS and BR9EYA and BR9ES. EYA is what Arctic Cat recommends for damn near everything they ever sold in the past. It has a V groove in the electrode that is suppose to help against fouling.

ECS has a low Angle ground electrode.

I've been running BR9EYAs in everything that calls for a BR9 style plug. They seem to work better for my old Touring E 380, but really haven't noticed a difference in the other sleds.

 

[440x]

Br9ecs would break up at 8000 plus on my 440 in race mode with a "tight" motor. Br9es resolved the issue. Both gapped the same. For what it's worth...