Bike wont start

Need some help gentlemen. I rebuilt the top end on my 07 ktm 250 sx with a 300 sx conversion kit not long ago. Have maybe an hour on it. I also installed a jd jet kit on there. Stock pilot, 162 main, red jd needle using the 3rd clip notch. Bike ran great. I purchased a fmf gnarly pipe with the turbinecore 2 silencer and installed it today. I kicked it over and it fired right up. It idled for a minute or two, i then turned the throttle and it bogged down and died and refused to start back up since. I tried kicking it over and no luck. Any ideas?

Probably a fouled plug

get new plug

Ill try that. Just curious that if its the plug, why would it foul out? After i change the plug, wont the new one just foul out as well? How can i remedy this?

Not necessarily, could have been a combination of reasons. Put a new plug in, warm for a minute or so, ride lightly for a thorough warm up and then ride, see what happens with a quick plug read, etc.

Ill try it out tomorrow when the new plugs come in. Love amazon prime.

When you change stuff on a engine you have to re jet. If you don't understand BASIC stuff like this you need too start over again, back to mini bikes for u

Do not just idle the bike for minutes. Start it, let it idle for 10 seconds or so, and then put it in gear and ride it gently. Number one cause of fouled plugs is too much idling. Number two cause is riding too slowly too much. Number three is way too rich

Markit, i appreciate the douche comment when im asking for actual help. And for the record, i emailed JD jetting prior to switching my exhaust and they told me with my new exhaust setup that the jetting would suffice. Hence why i assumed it would be fine. Hey Pat, i appreciate the comment. However, i was under the assumption that these 300's were efficient at constant low idling. Am i incorrect?

On 11/8/2017 at 6:06 PM, Sgprelude711 said:

 

Need some help gentlemen. I rebuilt the top end on my 07 ktm 250 sx with a 300 sx conversion kit not long ago. Have maybe an hour on it. I also installed a jd jet kit on there. Stock pilot, 162 main, red jd needle using the 3rd clip notch. Bike ran great. I purchased a fmf gnarly pipe with the turbinecore 2 silencer and installed it today. I kicked it over and it fired right up. It idled for a minute or two, i then turned the throttle and it bogged down and died and refused to start back up since. I tried kicking it over and no luck. Any ideas?

 

With that symptom. I hate to say it...but I have "fixed" many guys bikes with this advice.

Was the fuel valve turned to "on"?

5 hours ago, Sgprelude711 said:

 i was under the assumption that these 300's were efficient at constant low idling. 

I've never heard of a high performance bike that liked idling. Maybe some trials bikes, but not enduro/trail/mx bikes. No way a SX is going to like idling.

Is the spark plug black?

On November 10, 2017 at 8:04 AM, pat22043 said:

Do not just idle the bike for minutes. Start it, let it idle for 10 seconds or so, and then put it in gear and ride it gently. Number one cause of fouled plugs is too much idling. Number two cause is riding too slowly too much. Number three is way too rich

Respectfully disagree, I can idle for as long as I need/want to, I never foul plugs, same goes for my sons KX 100.  I do make sure carbs are dialed though.  Even if my bike loads up a little, one crack of the throttle and it cleans itself out.  Different strokes for different folks....

Changed the spark plug to a br7es. It had the br8ecm. Apparently the 300's need the 7. I cleaned the air filter and re-oiled it. I also moved the main needle clip from 3rd line down to the 4th to adjust for the cold weather. Before starting it, i checked the fuel lines going to the carb since it sounded like it crapped outve gas. The fuel line from the petcock was barely letting any fuel out. I drained the tank to find a peice of a sticker film looking paper was in there. Refueled it up. Running like a raped ape lol thanks for all the help everyone. Truly appreciated.

Didn’t see where you’re located but if the pilot is a 35 it’s going to be way too lean unless you ride at higher altitudes. I’m assuming the 300 kit had the SX head. Had lots of 300s and allowing them to idle cold meant a plug change in the near future. The BR8ECM is for the 250SX with the better ignition and is a good choice for the 300s using said ignition.

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