No rpm but idle

[Timconijn]

Hallo i,maar from the netherlands and have a bf20 honda foustroke . The did run fine yesterday almost at quarter throttle until i wanted to speed up it stallen. And from then on it want to not run more than idle . If i touch the throttle Just a little bit it runs rough and looks likes its stalls . Only when i move the trottle really slow it sometimes goes in to higher rpm. Thats only in neutrall .The idle screw doesnt seem to work.
I have checkt to carb. And no dirty stuff or water

What could this be
Ik have a link to youtube to show the problem

 

[MattFL]

My initial impression is a carburetor issue. Did it sit with gas in it for some time? Give the carburetor a good cleaning, shoot cleaner and compressed air through every hole. Or before that, squeeze the bulb on the fuel line. If that temporarily resolves it then look for a fuel pump issue, dirty filter or air leak on the suction side of the fuel line somewhere.

Also maybe it's just the mic on the camera, but it sounds like you might also have a noisy lifter, maybe the clearance on a valve or two is a just a little on the big side, an easy adjustment would fix it. Or maybe that camera just records that frequency really loudly and it's not so noisy in person.

 

[Timconijn]

Well its not the fuelpump. Because when i squees the fuel bulb it doessnt get better . I cleaned the carb en it didnt work

And the mic is noisy haha

 

[MattFL]

If you open the throttle and tap the choke (or put the choke on 1/2 or 3/4 if you have a manual choke), does it run better for a moment?

 

[Timconijn]

I dont have a manual choke

 

[MattFL]

I suspect something is wrong in the carburetor, probably the main jet clogged. When you cleaned the carburetor did you fully disassemble it and shoot cleaner and compressed air through every hole?

 

[Timconijn]

Well i have cleaned the carb and it works fine . But it seems likes its runnen on 1 cylinder. When i pull the top sparkplug . It doesnt change in rpm or running and when i pull the bottem plug it stalls and won,'t start and with the top plug disconnected it starts but runs rough

 

[MattFL]

That's definitely a clue, though even running on 1 cylinder I would expect it to rev when you open the throttle. But for sure there's a problem with one of the cylinders, so next check the bad cylinder to be sure it's getting a spark.

 

[km1125]

On two cylinder motors you have to be careful when troubleshooting by disconnecting spark plug wires. If it's a siamese coil, then both plugs fire at the same time and if you disconnect just one end and do not ground it you may cause a problem in the coil, as all that voltage needs to find a "ground" somewhere when the other cylinder fires. You should definitely ground the disconnected plug wire for proper troubleshooting and to avoid damaging the insulation inside the coil.