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Discussion Starter · #1 ·
I'm running a 2003 F5 Team Graphics carbed model. It came factory with 380 main jets, seemed a little fat, plugs were black. I changed over this year to 350 mains. I checked the plugs after a 1/2 to 3/4 mile run wide open, and the plugs were pretty white. I'm now going to 360 mains, which were factory from 04 and on. Temps were 10-12 F.

Anyone running 350 mains, what do your plugs look like? I ran the rest of the day part throttle to keep from burning down, and the plugs looked great at part throttle. If the 360s still look lean, I will go back to 380s and run it fat. I don't think there were any engine/carb changes from 03 to 04 that resulted in the different size main jets from the factory but I am not sure. If anyone knows, I would be interested to hear about it. Thanks.
 

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Ive heard of some running 350's, but think 360 is the norm. Dark plugs could be due to heavy oil usage. Good idea to keep an eye on piston wash along with plug color. 03's were pigs on oil until adjusted. Only difference was the o3's had a 1/2 or 1 degree more timing than the rest.
 

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Discussion Starter · #3 ·
Thanks. I am a little rich on oil, 37:1. I am planning on 1 turn on the nut which should get me close to 50:1.
 

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I tried 350s in my '05 F5 with a 2 degree timeing key and the plugs were very white so I went back to the stock 360s.
 
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