Severe Backfiring

I own a 2000 wr, It quit running after I last rode it, I now need to light candles to start it. If it does start it back fires thru the exhaust,will not idle and will only stay running if the enrichment knob is pulled out. I have adj the valves to spec, changed the plug, totally cleaned the carb,the filter,made sure it has fuel,went thru the ignition..resistance check. I changed the coil out with a buddies also his CDI unit! I have done everything I can think of. If any one has any suggestions please please help!

How about your hot start circuit? It sounds like it's running way too lean. On the 99 models, there's a hose connecting the intake manifold and the hot start switch. Could that be leaking air into the manifold? Good luck.

1: Did it back fire on decelleration BEFORE you pulled the carb?

2: What is the Fuel Screw set at? Is it at the same setting as before you totally cleaned the carb? Might also check the 'throttle stop' setting (internal to carb) - see the 'how to' in the technical section of this website.

Brian

Originally posted by Rich in Orlando:

How about your hot start circuit? It sounds like it's running way too lean. On the 99 models, there's a hose connecting the intake manifold and the hot start switch. Could that be leaking air into the manifold? Good luck.

This is the first thing that came to mind with me as well, when I read your post. ON a healthy WR with the engine on a stand and idling, I can pull the hot start and the engine will soon die. If I rev up the bike with the hot start on the worste backfiring I have ever experienced will happen when I De-rev (let it go back to idle).

If you are using the hot start to start the bike and leaving it on to keep it going, the first thing to check is your fuel screw setting.

mike

I had the same kind of problem with a 2000WR. The strange thing is that it only seemed to act up with a full tank of fuel and if I drained and filled the carb before I started it it ran OK. I drained all the fuel into my van, removed the petcock to check the filter, (there was a little IMS tank material on the screen but not enough to block it) and put in fresh fuel.

Problem gone!

I'm assuming I had some water in the tank and it was causing the missfire.

Easy enought to give it a try.

Good luck.

exactly what do you mean by totally cleaning the carb? was it removed from the bike, taken apart, any adjustments made (fuel screw or needle etc)? did you remove any jets?

when you adjusted the valves, was the timing chain moved and or repositioned correctly?

sounds to me like it probably has something to do with one of those things mentioned. go back and recheck everything you touched after your last ride....and good luck.

Chuck

I had the exact same symptons. My solution was cleaning the carb. I think the 3rd or 4th time going through the carb finally did it. It took alot of patience. good luck

i had this problem once and my kill switch was bad. I checked all electrical connections and it wasn't getting a good enough spark. If you dont have a good spark might be something to check. Does it have a malcom smith dual sport kit on it? Just checking

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