Orion RBX150 Cuts out at speed

[sasquatch]

Not sure whats going on here. Bike will run all day and wheelie for days. The problem starts when trying to sustain highway speed. I can cruise up to 45 no problem. Anything faster the bike will die out after a minute or so. I can cruise at 55-60 for about a minute then the bike shuts down like its out of fuel. I will engine brake down to 2nd gear, then the bike will take off again. Like nothing happened. I have ridden wheelies in 2nd at much higher rpms for about a mile with no problem.



Have tried bypassing the petcock thinking there was a restriction. No restriction in the tank. Carb is a nibbi vm26 float is set pretty high, have tried bigger jets as well. Runs great except for highway speed. Kind of stumped.

[Michigan Sportsman]

The culprit is…
A. Fuel
B. Air
C. Spark

My legendary expertise says, “C. Spark”.

… ladies and gentlemen and remember I’m pulling for you, we’re all in this together.

[sasquatch]

I was thinking a spark problem, but why never at lower speeds? Ecu problem? Ign pickup? I have ridden at similar rpms for longer times in lower gears.

[franque]

I would check the float height and make sure that the tank is adequately venting. It could just be that under higher loads, the engine is simply consuming more fuel at top speed than at higher rpms at lower gears.

[Nospark]

The sustained speed puts the most demand on fuel volume. In my experience Spark tends not to be intermittent with electronic ignition, i.e. CDI box.
I would address fuel first, if your confident in float adjustment and fuel volume delivery, I'd look at air flow. Check for either a leak on the intake side or, restriction of air volume. Lastly, spark.
That's just me. I'm told I have have no common sense. You can return my advice for a full refund.

[Megadan]

I would say it's fueling related. Throttle position dependent, which would be a jet or other related setting. Holding a higher speed generally means more throttle is needed. While your are playing around with wheelies and mashing the throttle off and on, you aren't staying in a position long enough for the fueling to equalize and reveal itself, plus the float angle changes during a wheelie, changing the fuel level in the bowl which also affects fueling.

Can you state about what throttle position you are at when trying to hold that 55mph?

[sasquatch]

Generally full throttle through the gears then once at 55 1/4 throttle or more. It will hold 55 with 1/4 but can take more if there is an incline. I can get past 60, but more throttle. Last night I adjusted the float height for more fuel in the bowl. Took a short 55 cruise with no problem. But its kindof random when it does it so I'm not sure if the problem is fixed. I'm not sure exactly where fuel height should be for the nibbi. Now it looks like I have it about level with the bowl seal.





I actually tried going up and down in jet sizes for this problem. The bike runs best with the current jets. Plug has good color with these jets.

[Thumper]

I agree it is a fuel issue...

But if it runs fine for a minute or more at speed, it is not likely to be the main jet size (I mean, why would that change?). It COULD be some junk in the bowl that lodges up on the main jet when cruising for a while (no wheelies to dislodge it, etc?), but I think this is a long shot. But easily checked (messy carb removal, but doable pretty quick!).

The float bowl valve, on the other hand, could have enough of something blocking it that it generally does OK, but when more continuous fuel is drawn, a vacuum develops in the bowl.

If you really know that the petcock, input flow from the tank to the the carb is not blocked or partially blocked, I'd be thinking float bowl valve, and would notice it there was crap in there.... I think you were on the right track, based on symptoms.

But you just adjusted the floatbowl valve. So even THAT doesn't add up