I had a small fall taking a turn at the mx track. The bike landed up on its side, I quickly hit the kill switch, stood it up and turned it on again. I was able to ride for a few seconds before I felt the bike loose power and it shut off. I wasn’t able to turn it on after that.
After getting home and unloading it, it would turn on and idle for about 3-10 seconds before dying.
I thought maybe it got flooded so I turned the fuel off, opened the throttle and hit start switch about 8 times before trying again… it would turn on but only idle for a couple seconds. So it was happening consistently.
I then proceeded to clean the air filter thinking maybe fuel got in there, replaced the spark plug, as well as emptying the float bowl and cleaning the carb jets. From there I started messing with the mixture screw to see if maybe something got out of whack, now I’m not able to get it to idle at all.
For context, it’s a 2025 KLX140rf (9 hours on engine) with a Mikuni VM26 carb I got from TBolt: https://tboltusa.com/store/tbparts-vm26-carburetor-kit-for-klx140-p-11755.html
I’m attaching a video of what the bike sounds like when I try to start it.
any advice on what what troubleshoot to get the bike up and running again?
Have you tried a new spark plug?
Yeah, I forgot to mention it in the post. I had picked up a new spark plug when replacing the air filter. I’ll give it another check today to see if it fouled when messing with the mixture screws. I have a spare laying around I can replace it with if so.
Have you checked the tip over sensor to make sure it didn’t get dislodged?
That could cause the problem you’re describing.
Also, you’ll need to to put your fuel/air settings on the carburetor back to the base settings too.
If you don’t have a service manual you should be able to find the info online with a little searching.
Where is the tip over sensor located?
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Well, it may not have one, but if it does it’ll likely be under the seat, or behind the front number plate.
Also, it wouldn’t be a bad idea to check all electrical connections, grounds, and engine start/stop buttons.
Hopefully the OP gets it sorted out quickly and back to riding.
I didn’t see a sensor but I checked the spark plug it was fouled and smelled like fuel… this is most likely when I was messing with the air mixture screw.
So I went ahead and cleaned it, I tested the spark and def saw a few. So I put it back in and reset air mixture screw to 1 and 1/4 turns out. I also turned out the idle screw quite a bit… I was able to get it to turn on and then it reved up and quickly died.
I’m not sure if at this point my issue is purely from messing with the carb or if I haven’t pin pointed the original issue I had at the track. It’s been a couple weeks now so I def want to get back on the bike. Any ideas from the video?
If it was me, I'd use a new plug and put the carb back to original settings.
When the tip over happened was the throttle open and then you hit the kill switch? That could have loaded the plug with unburned fuel.
Hard to remember at this point, it happened pretty quick… I remember the bike was still running and I just went for the kill switch and stood up fast. I’m either case one of the first things I did was replace that original spark plug, so the one from the images was a new one I put in when replacing air filter.
I def have a new plug I can use but putting it back to the original settings will be difficult. I had the carb put in with upgraded suspension (heavy duty fork springs and rear shock) and that was done by the suspension specialist I took to. Taking it to a shop just for carb tuning doesn’t seem to make sense, I’ve been quoted around $200-250 just to start work on it (Orlando/Kissimmee area).
I guess I can keep playing with the screws… I didn’t want to mess with the jetting since it was working just fine leading up to this.
In the video, are you using the choke to start it?
Yeah, the choke was out.
The way he set it up for me when it was first installed, there was no beee to use the choke… it would turn on first start. I’d like to get it back to that point but so far I’ve been following the stock settings for the vm26, which I think is between 1-2 turns out
Fouling a plug on a KLX140 is not very common, and with the carb settings changed, seems like that could be the culprit.
Was the temperature colder when you did not need the choke? If the temperature is warmer now, then it would explain the fouled plug, bike is running too rich. Also could explain why it starts but will not run.
You could try increasing the air flow with the air mixture screw and see if the situation improves.
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