ok , this is how goes. i broke the frame on my 400ex in june and it sat in the honda shop for 5 months while those people continued to screw up my frame order. when i got it all back and done it would not idle. i drained the gas and put in new gas. then i thought i may have had a jet clogged up so i reved it out and put the choke on hoping it would suck a bunch of gas thru the carb and clear it out but it diddnt work. i have ran a few practice races with the idle turned up pretty high hoping it would fix itself eventually but it hasnt. i have k and n airfilter and outerwear with no pipe so i havent put the jet kit in that came with the power kit i bought. it ran fine untill it sat for 5 months and now i dont know what the deal is. the other day i took my airbox off and fired it up in my friends garage with the carb exposed. it sputtered , popped and a big flame shot out of the carb. i dont know if this has to do with anything or not. plus i have not adjusted my valves yet and i got it the summer before last , rode it for a year , then it sat up for 5 months so i was wondering if i need to do that. i usually run at the track with no spark arrestor and no airbox lid. but no matter what combination of airbox lid/spark arrestor i have in it still wont idle. i am desperate here and i really hate working on carbs because nothing ever seems to run right afterwards. any information anyone has to offer would be greatly apreciated.

thanx ,casey

 

It sounds like you have a gummed up carb. The fact that the bike leaned out and started backfiring with the filter off supports that. Just to test the theory, take a rag and rap it around the filter, restricting the air flow, and see how it runs. It will most likely run a little better.
I would pull the carb off, get a can of carb cleaner and a wire brush and go to town.
If all else fails, I will be taking my stock carb off this week as soon as my FCR gets here. A couple bucks and it could be yours.

 

Gummed carb sounds right, also make sure you didn't pinch the rubber isolator(engine side) open any allowing an air leak around the carb. BTW there's nothing to be scared of working on carbs! There are a few simple fast rules. A clean work area, don't loose parts, remember how it went together( and original adjustments ), avoid tearing seals-they can be a pain to replace, don't use a drill to open up jets [img]i/expressions/face-icon-small-happy.gif[/img] , lastly avoid using stainless wire or the like to poke down passages, use a hearty spray-carbs spray's good-but brake cleaner is usually better...

 

I just had a similiar problem with mine. After a year of riding it just leaned out big time. Kept back firing and popping. With some good advice from a 400ex group I belong to and a drop of the needle clip to the 4 spot runs better than ever. Still dont know why it did it, I have a 160 main in it with a stock pilot for now. Try dropping the clip down one its very easy to do. Also make sure your filter isnt clogged this could be some of the problem..


Scott

 

All that you need to do is clean out the pilot jet, get some good carb cleaner and clean it out and also spray it into the hole that it came out off. After doing this it will run alot better. We have this happen to street bikes all the time because they let it set during the winter with gas in the carb. Whgen they start it in the spring, It will only run with the chock on..What happens is that the gas has dried up and the remains has blocked up the pilot jet.
This should get you running again.[img]i/expressions/face-icon-small-tongue.gif[/img]

 

thanx a million guys , ill be sure to break out the old brake cleaner and go to town, if this doesnt work , ill get back in here and ask some more!

thanx , casey