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Honda 400ex carb trouble

2166 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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Welcome to the forums! When was last time this carb was cleaned and had a rebuild kit put into it. Seems like your jets could need replacing.
I have a video of it running .. but I don’t kno how to post it .. also it idles decent wen I flip the choke on a little bit
Post it on YouTube then copy and paste it's link here
Unless I missed it I don't think you said you bought and used a rebuild kit. Need to get you one and replace the parts. Be sure on idle screw and fuel adjustment screw you count how many turns out you have to do. To do this before taking it out, screw it in and count how many hole turns it is and write it down. When you replace all that, clean everything and spray entire carb out with compressed air. Should be ready after that. Let us know what happens
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.
What's the oil for?
It serves as a temporary seal for the rings.
Ah clever. Thanks for explaining.

How much oil exactly would u put in? And how would you get it out if you decide you don't need to rebuild top end? Or would it be fine to leave it in there
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