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Honda 400ex carb trouble

2158 Views 21 Replies 5 Participants Last post by  SlammedRanger
Hey guys I’m new on here ... I have a 2002 Honda 400ex I’m workin on for my buddy... it has k&n air filter and a excellerater exhaust by DG performance... it idled fine but as soon as you got into it it would cut out .. unless you turned the choke bout half on then it would run pretty good .. I need a starting point for the carb .. jet size and needle position?
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Full pipe or just a slip-on? Air box lid on or off? And what elevation are you at? Welcome to the forums!
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Also forgot to mention it runs rich. Smokes slightly blueish oily smelling and plug was black crusty and dry. I'm assuming maybe new rings or valve seals? But could this also be an effect of my bike running like I previously explained?
Yes if its smoking blue that is oil burning. Does it do it worse when riding and revving it? Or only at start up then go away? If you are burning oil from bad rings you are losing compression. And will never get it to run perfect until its not. Your jetting to me sounds real lean for a full pipe, filter, and holes in airbox. I wanna say 118 is stock or very close to stock. I would be figuring about 4 to 5 steps higher on main jet for your mods. There isnt any chance it has a dyno jet kit right? Because a 118 dj is on a different scale then a oem keihin jet.
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42 pilot jet. 160-165 main jet. Should make it run alot better. Put the mixture screw at 2 1/4 or 2 1/2. I would also drop needle one clip down from top. My .02
If the jets dont say anything on the side sometimes the number will be etched into the tip near the nozzle. If there is actually no numbers they are mega genaric jets and god only knows what size they actually are. Get you some oem keihin jets for the carb from jetsRus or somewhere like it and start with my suggested sizes. I would jump to the carb being dirty until you have the right size jets in it. Your discription sounds spot on for lean jetting.
Yes it gets worse with revving and riding although I haven't had a chance to rude it far enough or long enough to determine whether the smoke goes away or not but I've let it idle till warm and red it and still smokes. Not sure on how to tell if the jets are dyna or oem. Just says 118. I ordered an fmf power up jet kit, will hopefully be here tomorrow. I will switch the jets and reclean and see what happens. Do you think rings should be added to my shopping list as well?
Hard to say if its rings or what it is. You will need to do a compression test to confirm it. Do a dry test. Then put some oil in the spark plug hole and do it again. If the number spikes way up you need to pull the topend and see if its in need of a bore. You do this by mic'ing the cylinder. And inspecting for any scratches. You will need a piston and rings in what ever size the cylinder has to be bored and honed to. This is a job for an engine machine shop.
It serves as a temporary seal for the rings.
Usually a few ml. And it will burn out first time you start it. May smoke a bit blue for a few seconds.
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