Jump to content

ktm 125 sx quits running after refueling

Recommended Posts

My son rides a 2018 125sx in cross country hare scrambles.  Two weeks ago, an hour into the race, he refueled in the pits then continued on...bike went about 100 yards than quit.  Bike would start with choke on but wouldn't stay running.  We cleaned the carb, changed the spark plug, replaced the fuel, and replaced the air filter.  We got it to start and it ran okay as long as the rpms were high.  Entered another race last week and the bike ran great until an hour into the race he refueled and the bike died about 5 minutes later and wouldn't start (same as the previous week).  Completely frustrated, we bought a brand new 2019 150sx.  We broke it in last week and yesterday entered another cross country race.  Bike ran great but than quit an hour into the race after refueling in the pits.  Same symptoms as before.  It won't start.  We are mixing the fuel 40:1 and running 98 octane fuel.  Don't know what we are doing wrong.  Any advice is appreciated.

Share this post


Link to post
Share on other sites

Do you run a standard gas tank filler cap, as my first thought is vacuum lock?

Yooj

Share this post


Link to post
Share on other sites

Sounds like it's having a problem venting and as Yooj said it's vapor locking. Need to confirm all the vents are clear

Share this post


Link to post
Share on other sites

Everything is stock...I figured it was vapor lock...nothing else made sense.   I tried starting it with the gas cap off but that didn’t work.   I am brand new to motorbikes. Our local KTM dealer opens in a couple hours, I’ll be giving them a call. 

Share this post


Link to post
Share on other sites

Make sure whatever fuel jug you're filling the bike from isn't full of debris.

Put a fuel sock in the mouth of your tank.

Don't run those stubby cas cap vents.

Do a petcock position test, connecting a length of hose, drain into a bucket and open the petcock to ON to find the position where you get the most flow and mark it somehow. Do the same with the OFF position.

Change where you've been getting your fuel. Or at least test it for contamination and water.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×
×
  • Create New...