Just bought a 2024 KTM50sx with 2 hours on it. According to the paper work the previous owner purchased it two years ago. Given it has only 2 hours on it in those two years, I drained the fuel and put in some fresh gas mixed 60:1. I let my son ride it and it was bogging down when he’d get on the throttle, it would bog so badly the bike wouldn’t move and sometimes would stall out. I put the choke on and the bike stopped bogging and was actually rideable. I figured the jets were probably plugged given it has mostly sat the past two years.
I pulled the carb apart and removed the jets and cleaned every single passage and jet with carb cleaner and compressed air. I reassembled the bike and had the same problem. I did notice if I turned the fuel screw out the bog would lessen. I also tried raising the needle one notch but that didn’t help.
I have to assume this is a lean bog given putting the choke on made it go away, however I’m not too familiar with these things at all. Anyone have any suggestions? Everything on this bike is stock and it’s essentially brand new. I can’t imagine it’s jetted too lean stock so I feel like I’m missing something here. I can make it bog on the stand with both wheels off the ground by opening the throttle quickly. And while riding it when rolling on the throttle, seems to happen right before or just as the clutch engages.
Filter seated fully? Filter oiled enough ? Perhaps a crank seal popped out of place. Did you verify all the jet and needle sizes? Maybe previous owner monkeyed with it and put something crazy lean in it.
Yes filter looks seated and oiled properly. At 2 hours I would hope a crank seal didn’t pop out but anything is possible. The idle doesn’t hang like it’s got an air leak though. The previous owner didn’t do anything to the bike besides have the dealer lower it to the lowest height before he took delivery, I should have wrote down the jet/needle sizes while I had it apart to compare to stock, but I am pretty positive they’ve never been changed.
Sure you got pilot passage clean? Check reeds Change plug
yeah pilot is clean, I looked into the reed cage real quick when I had the carb off and didn’t see anything obvious. I’m ordering some plugs for it and will put a new one in just to see.
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Just took the carb apart again. Pilot is a 50, main is an 88, needle is a W7 in the second notch. Verified everything is clean, ran a couple strands of copper wire through the jets just to make sure. Verified vent hoses weren’t plugged. The screen on the fuel valve is clean as well. It only will do it when riding it coasting along and then whacking the throttle wide open. If you go maybe an 1/8 of a turn on the throttle and quickly go wide open it’s fine. Not sure if maybe this is a normal 50 thing?
Its too rich 45-80
I bought a couple different pilot jets, can’t seem to make it better or worse messing with the fuel screw so I’ll swap pilots around and see if that makes a difference. Bought a 45,48, and a 52. I did notice the idle screw is turned almost all the way in to get it idling which does lead me to believe it very well could be too rich.
Still can’t get this thing right. If I lean out the fuel screw it makes it worse. Richening up the fuel screw lessens it but doesn’t make it go away completely. Even though the bike isn’t running lean, I tried going the next size richer on the pilot jet and still has the same issue. I lve already tried moving the needle, I don’t think it’s a main jet as it runs perfectly fine wide open, it’s just that initial bog/hesitation going from throttle closed to wide open.
I saw a video on social media about a tiny pressed in jet on the dellortto 19mm carbs that claimed they can fall out with aggressive cleaning and leave you chasing your symptoms.
Maybe you want to find a new 19mm (or 21mm……
Hard to believe at 2 hours this thing would have a problem like that but anything is possible these days lol. Are 21mm carbs a common upgrade on these things?
Its the kind of thing you find on the Cobra Elite bikes
https://www.instagram.com/reel/DcJnkVDRTAG/?igsi=MXNoeGZmd3ZpZXE3Nw==
See if this works
Otherwise, I swear almost any oddity in running on these bikes can be traced back to the Stator. I know the 24+ have a different stator, but I think they are still all garbage.
Bike has a studder? - Stator
Bike falls on its face? - Stator
Chain too loose? - Stator
I don’t have instagram and for some reason it won’t let me click “continue on web”. What’s on the video?
Yeah I’ve always read you should keep a spare with you at all times lol. I have heard the newer ones were better but who knows. Again, with 2 hours on it I can’t image that could be having issues but I’m really at a loss here.
Maybe there’s more to the “2hr” story? Forgot to put the air filter on…coolant puking new rider afraid of the bike…. If the bike runs like shit, not much to lose by further investigation
Is the fuel petcock flowing gas at a good rate?
Yeah it flows properly, I pulled it off the tank to make sure the screen wasn’t plugged too. The bike was super clean and completely untouched… but yeah who knows if in that 2 hours period it got overheated or something. I did check coolant and it’s full, and it’s a pink color, which I believe is what these come with. The only thing I haven’t tried is going up on the main jet, so I’m going to order the next size up and give it a try. I looked into the reeds when I had the carb off and didn’t see anything, but maybe I’ll pull them and inspect them just to make sure something isn’t holding one open or something.
Can you adjust the stall on your clutch, engage at a higher rpm
Pit Row
Yeah clutch is adjustable. The hesitation/bog happens before the clutch even engages though. It’s happens instantly when you twist the throttle wide open.
You have the bog baffle facing the right way? Something it’s causing a lean condition. Float height not correct, air leak, wrong jetting, it’s gotta be something.
Yeah if you’re referring to that baffle around the main jet, it is installed correct. I have checked it for an air leak and didn’t find anything, and it doesn’t run like it has an air leak (does not idle high, idle does not hang). It’s definitely running rich at idle now but it’s the only way I can lessen the bog/hesitation. I did order the next size up main jet so we’ll see what that does.
I think someone has put too lean of a main in which is throwing everything off. I run a 48 pilot and a 90 main on my son's 50 which fixed the fouling/spooge issues and it starts and runs great. I believe stock should be a 95 so that 88 has been put in by the previous owner.
According to the manual the 50 pilot and 88 main are what this bike comes with and are correct for my altitude. I did buy a 90 main that just came in today that I’m going to put in and see what it does.
Well the 90 main didn’t change anything. Starting to think it may just be the way these bikes are. 95% of the time the bike runs great, I can only here it bog when he’s riding and snaps the throttle wide open from completely closed. The plug looked great on the stock jetting and leaning the fuel screw seemed to make it worse but may start leaning it out a little just to try something.
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