Posts
4245
Joined
10/5/2017
Location
FL
US
Bike was jetted when it was brand new in ‘16. Always ran good down here never had to mess with jetting or even the air screw. Last weekend I raced the bike in a harescramble and ran great for the first hour but the last half of the race the bike would run fine low to mid but once I got to the powerband it would just spit and sputter trying to rev out. It didn’t die on me, but the poor thing could not get out of its own way and didn’t seem happy. I was able to limp it to the finish.
Reeds are good, no gaps
Plug is coffee brown colored, run a BR9ECMVX (Stock plug)
Tried a different plug but got the same effect
To note, I’ve had some issues running a big tank on this bike, usually fuel delivery related. Bike ran fine the last two weeks before the HS, then I put the big tank on and it ran like dogshit again. I've had some other weird issues when running the bigger tank (Can't say the tank was to blame), but only had those issues at off-road races where I swapped to that tank. Tried taking off the cap to see if the tank isn’t venting but got the same effect.
Reeds are good, no gaps
Plug is coffee brown colored, run a BR9ECMVX (Stock plug)
Tried a different plug but got the same effect
To note, I’ve had some issues running a big tank on this bike, usually fuel delivery related. Bike ran fine the last two weeks before the HS, then I put the big tank on and it ran like dogshit again. I've had some other weird issues when running the bigger tank (Can't say the tank was to blame), but only had those issues at off-road races where I swapped to that tank. Tried taking off the cap to see if the tank isn’t venting but got the same effect.
May as well just put a new one in it.
The Shop
So you've had this problem before with the big tank?
If "YES" then I would take it back off and see if the problem goes away. If "YES" then you need to figure out what the problem is, or what is different about the big tank that makes the bike run like crap.
Started up and idle and revved good for the first 30 seconds, increased the revs to the powerband and the bike sputtered, backfired, and just sounded terrible. Also has a bog right off idle when I snap the throttle.
Cleaned petcock again, checked silencer packing, leaning more towards something electrical.
Put another fresh plug in, bike replicated the issue again so I pulled this plug and was blown away at how rich it was. No rag in the air box to starve it for air, played with air screw, made sure PV was functional yadda yadda yadda.
Decided to flick the choke on and when I pulled my choke up it dropped right back down. Was puzzled so I pulled the mechanism out and the actual plunger and rod were stuck/lodged into the carb. Had to use some vise grips and some muscles but got it out and put another one from my other KTM on. Took it to the field down the street and ripped 3 starts to 3rd gear and bike ran stronger than it ever has since the whole rebuild 5 hours ago. I appreciate everyone’s responses and advice to help me the 125 back together, hopefully this post may save someone some headache down the road.
Post a reply to: KTM 125 sputters in powerband