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one spark plug lean...one rich

4672 Views 8 Replies 4 Participants Last post by  4everrunning
I just installed an Area P full exhaust on my 08 250R as well as a Dynojet kit. I was hoping the recommended settings would work but...of course not. It is running poorly below 4500 RPMs. I have now moved the needle lower and it seems to be running fine now.

However, that is not what this post is about. After removing the spark plugs, that were used with factory settings, one side appears to be running lean while the other running rich. I have not tried to sync the carbs as none of that has been touched. I do know that the factory settings for the fuel/air screw is different for each side. Could that be the reason one side shows rich and the other lean? Should I have the carbs re-synced?

Any advice would be appreciated.

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It wouldn't hurt to re-sync the carbs. If it's just a small difference, and the engine is running fine, I really wouldn't worry about it. The gap maybe a little off on one or both of the plugs. I would imagine that even the index of the plug (read: the way the electrode points) would make a small difference in plug color.

If the bike has over 1000 miles or so on it, and the carbs have never been re-synced, I would say that a re-sync is going to do it. The initial service on the bike calls for the carbs to be re-synced.

The carb work during the first service, from what I gather, is really the only critical thing besides the oil change. Every bike tech I talk to says that the valves are almost always in spec, but the carbs almost never are.
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