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Discussion Starter · #1 ·
Can anyone enlighten me on how to tell if the carbs are running lean? I have a 96 m900, I just installed flat slides and it runs pretty good but not smooth all the way thru the rev range, I have checked the plugs and they have a light white powder on them, not the healthy normal color. Any help would be excellent
 

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I think you just answered your own question... Dry white plugs indicate a lean condition.

To determine which circuit(s) is/are lean you'll have to do a plug chop while running the bike at different throttle positions.

Using higher octane gas will help to minimize the effects the lean condition until you can correct the jetting.

--Fillmore
 

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when FCRs are only a little too lean, they crackle. when too lean, when the throttle enters the "circuit" which is jetted too lean, the bike acts like you hit the kill switch.

given the awesome isolation that the FCRs have between each different circuit (and their corresponding throttle position), i have seen this happen at WOT (main jets) as well as at 1/4 throttle (needle root diameter).

check out my FCR FAQ:
http://www.ducatitech.com/2v/fcr_faq.html

:) chris
 

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You can temporarily "richen" the mixture by blocking off some of the air intake area so that less air gets through. Find an open area where you can make some acceleration runs and bring along some duct tape. As you block off the intake area, it will run better if it was lean. The stock Monster has less than four square inches of intake area throught he snorkels, so you can cut down the intake quite a bit before choking it off completely.

I used a similar method of blocking off the intake area to determine that I needed to go up one more jet size on my bike. I left it blocked off until I had time to pull the carburetors again and get it right.
 
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