Long term ownership issue with OKO K101 carburetor

[David Lahey]

I've been enjoying the performance benefits of OKO K101 carburetors on five of my old bikes for many years.
Because they work so well, I've been recommending them for use on two stroke twinshock trials bikes.
Because I've always banged on about how good they are to anyone who would listen, I thought I'd better also mention some maintenance that mine have all now required.
The float needle tip is rubber and eventually deforms where the tip touches the seat. The deformation is a circular dent in the rubber. The dent in the rubber tip causes the float to sit higher in the float-valve-closed position which causes the fuel level to sit too high in the float bowl. The fuel level being too high causes the air/fuel at low throttle openings to become too rich. When this happens, engine response when the throttle is moved away from closed position becomes poor and unpredictable. This is a bad thing on a trials bike. Because this issue develops slowly over many months, it may not be easily noticed.
Adjusting the idle air screw to improve the fuel/air mix at idle makes a difference but does not completely eliminate the poor running.
To fix it, you can either fit a new float needle or make an adjustment to the angle of the brass tab that pushes on the float needle.
I suspect that the issue may happen more rapidly in bikes that are transported or stored with a full float bowl or have a passing fuel tap, because those things will cause the float needle tip to be pushed against the seat for long periods.

[Bully fanatic]

I agree completely on that one David. I have bought a new float needle for one of mine and my M199 will need one soon.

[David Lahey]

I agree completely on that one David. I have bought a new float needle for one of mine and my M199 will need one soon.

Graham, I've just ordered some new float needles because the one on the Majesty only worked well for a few days after I adjusted the float tab then played up again yesterday. I see the groove is not all the way around the tip and I suspect it sits poorly against the seat now. One good thing came out of it though. Because of the float needle issue, I've started testing the fuel taps on my bikes and found that the one on the Majesty passes fuel. Time for a new fuel tap.

[brent j]

I agree completely on that one David. I have bought a new float needle for one of mine and my M199 will need one soon.

I was starting to think I was losing my mind!

My RL ran beautifully with the OKO and over time got harder to restart if I stalled or turned it off.
Symptoms of loading up, kick, kick, kick and it will start and blubber away with the throttle wide open etc.

Due to the old adage of most carb problems being ignition (how can a carb go bad if nothing has changed!!??) saw a new coil and cap fitted (correct resistance) and swapped CDI and Stators.
All to no avail.

Then stripped and cleaned the carb and float level seemed to be on spec.

Nothing to lose now so lowered the float level and it ran better and was mostly easier to restart.

Better but not right so lowered the float again for a better result again. Easier restarts and better low throttle response.

Now after reading this, I'm tempted to lower the fuel level again and if that's better again, I'll look at putting it back to std and replacing the needle. Looks like they may be a consumable item.