Joined: Dec 2004
I had that happen to me once, double check to make sure the front carb is seated in the rubber boot to head, its a son of a gun to get it seated, I use a long bar and pry it down to snap it in place. If it isn't seated completely it will run way too lean, something to check for anyway
Originally Posted by WhereTheHellIsJames?
Iím at a loss. I canít seem to figure out what is going on with this bike, and itís driving me nuts. It all started towards the end of March on the n00bs ride in Death Valley. Many people there heard about Ďthe broken KTMí, but so far, nobody has been able to present the solution.
Details of the bike: 2006 KTM 950 Adventure. Canisterectomy, flappendectomy, SAS removed, ran fine, then just started not running fine- no major event, no revving, no nothing. Out of nowhere, while maintaining a steady RPM on the highway, it just started running crappy on the front cylinder.
Hereís the dealÖ
Riding along the highway between Panamint Springs and Furnace Creek, something happened. No clunk, no thud, no whap, no nothingÖ it just started not wanting to run right below 6k RPM. When we pulled into the fuel station at Furnace Creek, the clutch was pulled in to coast up to the pump, and the engine died. Weird, but whatever- thinkgs like that happen sometimes. When we go to ht the trail, the bike is hard to start, wont idle, and is popping a bit. I figure that maybe itís flooded, or thereís a piece of debris in the carb thatíll work its way out in a couple of miles, so we head up the road. Things donít get any better after a few miles, so the decision is made to stop, figure out whatís going on, and try to fix it.
Turns out that itís the front cylinder thatís popping, and itís acting like the jet is clogged. Off come the crash-bars, fuel tanks, glovebox, airbox, and carbs, and I opened them up for a quick service right there in the middle of the desert. Nothing- those jets are clean as a whistle. Thinking that maybe whatever was stuck in the jet had fallen out when I drained the float bowl, it all went back together. Turn the key, fire it up, and pop, hmm hmm pop pop hmm pop. Still the problem persists. At this point Iíd been holding up my friends for an hour in the middle of the day while we tried to fix the bike. I knew that my ride was over, so I sent them on their way and headed back to Panamint Springs on the bike.
On the highway, it rode like one might expect- not as good as it does when all is running perfectly J It did keet a normal temperature though, and didnít seem to be struggling terribly. When I got back to camp, a thorough cleaning was in order. I spent the rest of the day pulling it apart, going through that front carb extra carefully, then put it all back together. Turn the key, and Ö hmmm pop hmm hmm pop pop hmm pop. WTF?! I sought outside help, and Lior stepped up to the plate and offered assistance. We worked on that bike until around midnight, and never did out whet the heck was wrong with it. Some other forum members offered up some spares, so we replaced the plugs on the spot, swapped coil packs front to back, as well as bypassed the fuel pump and used brand new super out of Liors tank. A valant effort on the part of the community, yet the problem persisted, and the front cylinder continued to pop and backfire. We were out of ideas, and it was late.
The next day, a VERY COOL forum member set me up with a loaner bike for the day, and I got to go ride. It was my first trip to DV, and I was super stoked to be a part of a community so caring, that they offer up a spare bike when mine was beyond field repair. Another VERY COOL forum member drove me and the KTM all the way back to San Francisco when the trip was over. To all that contributed- you know who you are and what you did for me, and Iím so grateful. Thank you.
Continuing onÖ the bike is back home, and Iíve had it apart now more times than I care to admit, and itís still misfiring on the front cylinder. Seriously, WTF. Iím at a total loss here. The carb is probably cleaner than it came from KTM, the valves are in spec, the cams are where they should be, fuel is getting to the carbs, new boots (not that there was anything wrong with the old ones) but still, that front cylinder keeps on backfiring!
It seems to be a lean conditionÖ
When the bike is running, and you look down the carbs, the slide on the rear carb is going crazy like it should, but the front is hardly moving. It pops humms pops pops humms, etc. When I put my hand over the front carb, the popping stops (this is why I say a lean condition).
Hereís what Iíve done:
* Cleaned that front carb like I never have beforeÖ like 5 times. Carb cleaner, compressed air, banjo string, the works. Lior cleaned it twice too.
* Checked and confirmed that the valves and cams are in spec. They were. I thought that maybe the cam chain had somehow skipped a tooth, but it didnít.
*Replaced spark plugs, and swapped coil packs front to back to see if the problem switched cylinders. It didnít.
* Replaced intake boots.
* Drained old fuel completely, and put some fresh non-ethanol stuff that I bought while in Oregon last week in it.
* Checked all the fuses, and moved them around / swapped positions.
* Cleaned fuel lines from the connection halfway down the left side all the way up through the T and to the carbs.
* Thoroughly checked/cleaned (not that it needed it) the bellow that the needle attaches to.
* Removed the SAS system and installed block-off plates / plugs.
* Confirmed that there is no air leak where the canisterectomy bolts were installed.
* Replaced the vacuum lines (for carb-synching) on the right side of the manifolds.
* Ran the bike without the airbox on it, placed my hand over the front carb, and sprayed carb cleaner and starting fluid around the boots and intakes to confirm that there were no air leaks there.
* Confirmed that the valves seating by turning the engine to TDC, and spraying carb cleaner in the manifold. It pooled and sat on the valves overnight, with no change in fluid level. (yes, I sucked it all
out before turning the engine over again)
* Slaughtered a chicken and lit some candles.
* Finally, after a month of trying to fix this on my own, I wrote this long-winded post.
So thatís where Iím atÖ out of ideas. If your suggestion turns out to be the fix to the mysterious front cylinder backfire problem (and no, taking it to a shop doesnít count), Iíll send you a set of Pie-Hole makers. Also, if you have a spare front carb, and youíre 100% certain that it is 100% good, and youíre willing to loan it to me for a quick test to confirm that I'm not completely inept at cleaning the carb that's on this bike, Iíll gladly pay the shipping costs both ways, and do something cool for you.
Some very bright KTM folks are stumped on this one. If you figure it out, youíre a hero.