exhaust making fire

[the fat kid]

so we went riding this past weekend, and my motor was acting kinda funny anywasy, it would like randomly bog out and die id have to turn up my idle screw just to get it to run at idle cause any thumb throttle would kill it, and well it was shooting some flames out the back too and some backfiring, any clues, its a z400 2004 slip on, jetted, k and n filter. thanks...

[honda6490]

Try throwing a new plug in there first off.


Zach

[400exrider707]

What jetting are you running, it is terribly off.

[GPracer2500]

If it ran fine before and this just appeared out of nowhere then something's clogged and you're not getting the right amount of fuel.

[the fat kid]

not the right amount like its too lean. and yeah it ran perfecto up untill maybe a month ago, is there a fuel filter on these machines? thanks for the responses and gp where would you suggest starting the search? if i ride alot of mud and water is that likley the culprit? sorry so many questions im semi noobish.

[GPracer2500]

Backfiring and flames usually means lean but it can also be caused by way too rich. Anything that causes intermintent missfires will send unburned fuel into the exhaust. This fuel will occasionally ignite leading to flames and backfires.

Start with the easiest things first.

Air filter clean? (would cause richness)
Inlet into airbox obstructed? (would cause richness)
Gas cap vent clear? (would cause leaness)

The fuel strainer is integrated into the fuel petcock. You must remove the petcock from the tank to inspect/clean. (would cause leaness)

If that all checks out then it's probably a clogged pilot circuit (within the carb). Remove the carb, disassemble it and clean thoroughly with carb cleaner and compressed air. Bear in mind that if the fuel screw has never been adjusted then you'll need to remove the metal cap that's covering it (an anti-tampering measure) in order to remove it for cleaning.

It's also possible your lean because of an air leak. The usual suspects for that are the intake boot between the carb and the engine. Also check that the starter plunger assembly (choke) isn't cracked or loose where it screws into the carb.

[the fat kid]

thanks alot ill check all those sometime this week.

[Flyin400]

ya just clean the carb !

[the fat kid]

i guess it couldnt hurt to clean it all, idk ive just never been inside a carb im kinda nervous about taking it apart but then again no better time to learn...

[Flyin400]

Just try to keep all the little things in one spot so u dont lose them and rember how they go back on and u will be good.