[NCJake]

My 2007 KLR 650 has started running really rich. I bought it 6 weeks ago, went though all the basic maintenance, and have driven it almost daily since then without a single issue. Just this week it started running rich and stalling at stop lights. It carbon fouled the nw plug and I'm having to go to reserve tank at 200 miles after getting 250+out of the first 3 tanks I put through it. It smells like a gas station and blows black smoke at high rpm.
Should I start looking at the carb or the valves? I've been a hobby mechanic all my life and a professional off and on, I don't suck at it, but I am new to this bike, so any suggestions are appreciated.

 

[Tom Schmitz]

One thing that will cause it to suddenly run really rich is a stuck inlet valve. Fuel flows into the carburetor faster than the engine can take it in and use it.

Often, when the inlet valve is simply not sealing well, the engine will run OK at higher RPM but stall out at idle. With yours acting as it is the inlet valve could be stuck quite open. You may have a bit of selector gasket broken off and stuck in the valve.

Remove the bowl and remove the float and inlet needle, trying to capture anything that might come out so you can look it over. @pdwestman has recommended some polish on a Q-tip to clean the inlet valve seat. You can have a look at the inlet valve for hardening (possible on a 13-year-old valve needle) or wear, or simply replace it.

 

[eamartin]

I, too, would start at the carburetor. Inspect the float valve needle and look for any debris in the float bowl which, if there is any, could be a clue.

 

[eaglemike]

Agree with above. Sometimes the current fuels will gum up the float needle passage and the float needle sticks on the open position. Also seen them stock in the closed position.
It could also just be a small piece of crud stuck on the float needle seat. It can be so small it's hard to see unless you have good eyes and a good light.
Sometimes the petcock starts to deteriorate and gives off rubber bits that cause carb issues.
Is your carb setup stock? is your petcock also stock?

 

[pdwestman]

Just this week it started running rich and stalling at stop lights. It carbon fouled the nw plug and I'm having to go to reserve tank at 200 miles after getting 250+out of the first 3 tanks I put through it. It smells like a gas station and blows black smoke at high rpm.

All the other suggestions have validity. But I also wonder if the main jet might be loose & sucking fuel around the threads rather than only thru the center orifice.

It wouldn't hurt to check for a mouse nest around your air filter either! Sneaky Nasty little buggers.

 

[R/L]

I always go back to the last thing I touched when it comes to trouble shooting any problem. What was the last "basic maintenance" you performed?

Beyond back tracking, with a machine of unknown history, I'd go to the basics. Start with the air inlet side and ensure no restrictions there. After that, check all rubber parts for integrity.

Once sure everything is intact on the inlet, then consider carburetor. You should be able to check float level with a clear hose connected to the carb drain and routed up past the float bowl mating surface. Level with the engine running or vacuum applied to the petcock, should be at the mating surface. Too high float bowl level could be from a bad needle as mentioned above.

If I were to disassemble in inspect the carb, I'd pay close attention to rubber part condition and use a bright light to verify slide diaphragm and air cut off diaphragm integrity. I'd also be tempted just to do a complete rebuild using all new rubber parts including diaphragms. That is going to be a bit pricey but hey, its going on 14 years old!

 

[ymracing]

Very basic. Choke, enrichiner thingy, stuck open? Seen it happen.

 

[NCJake]

Thanks for all the suggestions. I've only owned the bike for 6 weeks so I'm learning about both it's maintenance history and it's lack of.
All I have done so far is changed the oil, the spark plug, cleaned a really gross K&N air filter and oiled it (not a too much oil issue) flushed the cooling system, bled the brakes, and topped off the battery fluid. I'm a maintenance junky so I'll end up going through the whole thing eventually. A Dookickey inspection is at the top of my list. I don't know if it's been done or not.
I'm just going to pull the carb and rebuilt it. For the cost of the rebuild kit I'm just going to do it and know what I've got. I'll check the choke when it comes out, but it is definitely a suspect. Any upgrade suggestions are appreciated.

Unfortunately, when I got home from my ride today I noticed that my left front fork was greasy. An hour later there was fork oil drips on the driveway. Guess what else I am doing this weekend.