My bike has recently developed major starting issues, seems to be getting worse. As for timeline:
Bike was running perfectly, used the battery in another bike and it died so bought same battery again. Seemed marginally more difficult to start
Over winter did a top end rebuild as general maintenance, everything was in spec. Started instantly on the button after the rebuild.
A couple of weeks later went to start and it wouldn't, it popped and backfired a lot, would occasionally just stop trying to turn over despite good battery charge, not holding the button excessively long and waiting between attempts.
Charged it and tried a few days later, no luck.
Took the cam cover off, still correctly aligned, intake valves had been at min clearance so re shimmed to mid clearance, no difference.
Went through wiring loom, verified no air leaks, nothing stood out, but bike suddenly started again. Took it out on track for a day, was a little hard to start one or two sessions, and took ages to start on track after stalling, but generally OK.
Raced the next weekend and it was an absolute nightmare starting hot and cold, nearly missed a couple of heats.
Since then I can barely get it to start, pops and bangs, generally won't start.
Rechecked clearances, all in spec, piston and rings all good. Replaced fuel filters, New plug, checked with a different coil, added a second earth lead from battery to front of frame, pretty much completely out of ideas for what else. Maybe the new battery is a dud and unreliable?
Any ideas? Racing in the weekend, not looking promising!
Maybe fuel pump Does it crank over easy or struggle? Popping is Electrical or timing This started after a rebuild?
It cranks over easy, until it may stop after a pop. The pump primes and sounds OK. I had the injector out and spray looks strong (though haven't measured pressure).
I do have to keep the throttle on to keep it from dying on idle, though once running on track it's fine
Finished one w same symptom Was fuel pump running no more than 2 bar with a load Changed pump and backfiring gone
In tank fuel filter? They can crack with time. I had similar symptoms with my 17 Fc450. I had one flame out while riding and a little popping on decel. I got home, washed it and had the same issues you talk about. Hard start, dying when trying to throttle up. The crack was obvious in mine. You can open your tank and hit the start button, see if you get a gurgling or strong whoosh kind of sound. I replaced it with a $11 auto filter from Napa Auto. Napa 3095 filter or Wix 33095.
Post a reply to: 2016 ktm 450 sxf hard start / backfires