Since my KLX was new (2010 model), if I let it sit for any amount of time, say, a month or more, it will foul the spark plug and won't start til I replace it. This is even though I turn off the fuel valve and drain the carb. WTF? I don't get it. I can park my DR650 for that long without doing any of that and it fires right up. But the KLX just won't do it.

I just got done doing it again... I'm running out of plugs. Gonna have to get a few more next time I'm at the store. But it had been in my trailer's garage for the last two months since I hadn't been riding it. I pulled it out since I may take it out this weekend, and sure enough, wouldn't start. Changed out the plug... still took a little while to get it to fire up (even backfired a couple of times), but finally did. And I put stabilizer in there too. Or more specifically, Marvel Mystery Oil since Sta-Bil doesn't do crap on this lousy gas we have.

Which brings the next question... is there a way to clean the old plug so I can reuse it? I've seen fouled plugs brought back from the dead before, but not without a lot of work. Was wondering if there was a simpler way. I tried spraying it off with carb cleaner first but that didn't help.

Rob

 

If you have a carb model, when you start it, don't touch the throttle till after it's running.

 

It is, and I don't. Have never needed to give it throttle to start it. In fact, it starts even easier now with the BB TM34.

 

Never heard of such a thing.

 

Well then your way, and I mean way too rich. Or the carb is messed up. Your the only one here this happens to. Sounds like your choke circuit is always on, does it run ok? Black smoke out the exhaust? I have my original plug with 10000miles on it, but don't tell anyone.
I never... never have had to use fuel additives.
I find everyone here runs jets that are way oversized compared to mine, not saying it doesn't work for them, but it don't for me.

 

[sarcasm]
EVERY KLX needs a 132 dj main and 38 or 40 slow jet!!! It's the only way!!
[\sarcasm]

Even when mine was running rich it wouldn't foul the plug. The plug was changed a couple times, but I think mainly to give the shop some extra business and keep a stockpile of extras.

 

My jetting is as follows:

135 MJ
37.5 pilot
Needle on third clip with nylon shim

I came up with this using my wideband O2 sensor and lots of test rides. If I go down any smaller on the main, I get a lean surge up top (and can see it go lean on the Wideband display). Ditto leaning out the midrange anymore.

Carb is a Bill Blue TM34... KLX300 exhaust, TwinAir filter, and KDX snorkel.

Rob

 

Maybe the oil ring is broken or all the ring gaps are lined up.

 

Given it did it when it was stock and still does it even after becoming a 351, I'd say unlikely...

Rob

 

I don't know, Rob. Plugs just about last forever in these bikes almost no matter what carb or settings are applied. If it's fuel fouling the plugs, it just about has to be something wrong with your carb...even then nothing jumps out at me. One example of how hard it is to fuel foul the plug on a KLX is a scenario I encountered on my Utah trip last month. I had to get off the bike in a nasty, downhill, rock section to open a cattle gate. It was hard to walk, much less get the bike to stay on the kickstand. While I was undoing the gate the bike fell over on the left side. It's pointed downhill, fuel is pouring out of the overflow and obviously down the carb throat, and I can't get to the petcock on Acerbis gas tank. The bike is off camber and jammed in some large rocks. I finally think to pinch my breather hose closed to help some, but it's a few minutes before I can position the bike where I can reach the petcock. It's even longer before I can actually stand the bike up. What a PITA.

Well, on startup I'm cranking and can tell the bike is horribly flooded. Still, with the throttle wide open that bike fires up quicker than I would have expected. Even drowned in fuel, the plug fires and runs fine the rest of my trip...and is still in the bike. It's darned hard to kill a 4-stroke plug in a bike like a KLX. Something else must be going on with your bike. It almost sounds a little like the air is totally blocked off during startup when you're having this problem, but that just doesn't sound reasonable. Is there any chance the something stowed under the seat is sliding over the air intake? Are you sure you have an air gap between the bottom of the seat and the intake hole? Those are crazy suggestions, but I got nothing else.