LANCE HAVANA 125cc cuts out at 40mph By smallville (Read 371 times)

[smallville]

She runs great but the minute I hit 40mph she cuts out so I have to let off the throttle. Unless I am mistaken she should go somewhere between 50-59 mph. I didn't break her in, bought her used. No other issues, the only problem is the cutting out at EXACTLY 40 mph. Any ideas why?

[kz1000st]

Look for a vacuum leak. Letting go of the throttle is a pretty good sign that air/fuel is being upset by something. Either a vacuum line or intake manifold is leaking.