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Discussion Starter · #1 · (Edited)
hey my name is mele im haveing trouble with my 400ex i just had a full yoshi exhaust and i tried rejetting it... the problem is that when i give it gas it dies, and before i rejetted it i gave it gas and it bogged down, it was fine if you gave it gas slowly but now it wont even stay running and when its given gass it makes a funny hissing sound in the air box/exhaust and then dies... also when it used to run, when you decelerated it puffed white smoke out
 

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Welcome to the forums. What size jets did you install? and try removing the airbox lid and running it. If you use a Dynojet kit it will tell you exactly what to use. Also your altitude will have alot to do with the jet sizing. Where are you from?
 

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Discussion Starter · #3 ·
the airbox lid is off and im using a kn with outerwears im using a 165 and my altitude is 2500 or so im from cali
 

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What was the stock jetts.And did you ad any pilot jet to it?
 

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I would remove the carb and give it a good cleaning to start.. also check the boots where the carb mounts on both ends. pull the plug too. what color is the electrode ceramic? 165 might be a bit much for yor elevation
 

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I would remove the carb and give it a good cleaning to start.. also check the boots where the carb mounts on both ends. pull the plug too. what color is the electrode ceramic? 165 might be a bit much for yor elevation
^^^^agreed
 

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that hissing is probly just your carb.since airlids off you hear it sucking in the air.isnt stock main like 148 or something?should only need to go up one or two sizes on the main.
 

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Discussion Starter · #9 ·
i shimed the needle with two spacers ill check it out today and report back
 

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Discussion Starter · #10 ·
yeah i think im gonna go 155 with altitude 3500 or so... i just want to ride :(
 

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let us know what happens.keep ur eye on the spark plug too.
 

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I agree with Moose and Sub. I would take the carb off and clean it good. It sounds like you may already have had a problem with the carb, before you tried to rejet.
 

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Discussion Starter · #13 · (Edited)
ok so i went down to 155 and dropped a shim off the needle its running solid now exept theres still that one problem where i give it too much gass and it boggs down... you can still get wot but you have to do it a gradually and still white smoke out the exhaust at full throttle and the spark plug is black and dry
 

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black is rich but if its the same plug try a new one then see.whats size is your slow jet?
 
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