bike is doing fine, but when i reach 4k rpm, motor starts to hesitate, and cant accelerate normally.
its like working on 3 cylinders. i can keep the speed, but my top speed now is 180km/h.
fuel consumption didn't rise up.

i changed spark plugs, ignition coils and wires.
i use supplement for cleaning carburetors.
nothing changed.

does someone have an idea, what causes the problem.
thank you, and sorry for my bad english

Is there a advance point in the ignition (that might start at 4000 RPM?)
Blocked fuel line? (starving the engine)
Gastank that draws a vacuum? (starving the engine)
Check if all the rubber booths on the carbs are still in decent state and mounted correctly... (air getting in the system in places it should not get in...)
Air box mice free (not a joke) and air filter not blocked or dirty?
just some point to check.

yesterday, we use stroboscope to check the ignition.
the interesting part was, that at first cylinder everything was ok, but at fourth we lost the signal at 4000rpm.
both cylinders are commanded by the same ignition coil.

today i will change again spark plugs, and wires.

any other things that i should do?

tmoons, what did you mean with that "Is there a advance point in the ignition (that might start at 4000 RPM?)"?

It is also possible that the carburettor for that cylinder is flooding...problems with the float

Originally Posted by shobo

yesterday, we use stroboscope to check the ignition.
the interesting part was, that at first cylinder everything was ok, but at fourth we lost the signal at 4000rpm.
both cylinders are commanded by the same ignition coil.

today i will change again spark plugs, and wires.

any other things that i should do?

That is interesting. You could also move swap the coils over to see if the problem moves if the wire and spark plug swap don't work.

the problem is solved, it wasnt in the ignition.
anyway, i changed wires with NGK CR2(and it looks cool), and spark plugs(this time i bought denso).
than i swap the coils and nothing changed.the test with stroboscope was useless, because it didnt work with the new wires.

the problem is in the carburеtors, fuel level is good, membranes are ok, we just set the fuel mixture, and the bike get better.
now i need gunson color tune plug.