another 400ex carb question

[not2hi]

Just bought a stock 400ex carb to throw on our 300ex...148 main 38 pilot 2-1/2 turns on the bottom screw...

FYI, wiseco 11:1 .040 over, webcam, titanium valves and springs, FMF megamax system, no limit CDI, Uni fiter and holed airbox with lid

when we first put it on, it fired right up, ran a minute or two then died...wouldn't restart. Yesteday had the plug out for a while, popped it back in, fired right up and then died.

after further review, its fouling the plug, and gas is even the airbox, so its flooding...

guy I bought the carb from was using in his 300 an said it worked fine.

So i'm not even sure where to start - most jetting instructions start at idle, whereas i can't even get this one going for any length of time.

So I'm looking for advice on what to do first...

also, I'm going to buy some main and pilot jets for tuning, but not sure what sizes to buy (couple sizes smaller and couple sizes bigger for both?) and i guess a bunch of new plugs.

thanks
-mark-

[ezdaar]

Start with the Float, for every carb rebuild or modification for use on a different bike.
You always start with the float level. ATM I cannot remember what the 400 carb's float lvl is. look in the 400 forum for the answer.
Once that is set. Try refire the bike, it should fire and idle.
Just beshure to properly adjust your mixture screw. BTW its not just set it at 2 1/4 turns out...
If you need info on how. PM me and I will post it up here or something..
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As for properly jetting the bike. If you are smart, and I think you are. I would instantly look into buying a O2 sensor bung and plug, Along with a Wideband O2 guage and sensor.

This completly removes ALL guess work and plug changes from jetting a carb!!!!

Prosport has some nice ones that are resonably priced for what your doing.
IF~ you do buy a wideband (which is the ONLY way I tune nowdays, I got tired of wasting $$ on plugs.) Tune it for a nice 12.5-13.1 mixture. remember 14.7 is stoich, but as we beat the hell out of our bikes 14.7 is not recommended for trail or track use on HOT days. You WILL melt that piston! Go no further than 13.1!! and only use 93 or better fuel.

More info to come, once off work..