Motor cuts out at high speed

[mick29]

Im wrighting in for a friend of mine he has a 70cc motor on a MB When he goes over 40kms an hour the motor cuts out for a second and then goes again It happens about every 30seconds The motor was tunned on a dino and it didnt do it when it was tunned soon as it was put on the bike it started doing it Could it be a fuel problem Can anyone help or has anyone had the same problem ? thanks mick29 PS HAPPY RIDING

[BarelyAWake]

It could be a coupla things - but I had a similar problem and it turned out I needed to fiddle with the float level a bit, took a coupla tries BTW

It could also be the fuel cap isn't venting properly (test run w/it loose or off), the in-tank fuel screen is clogged/restrictive (remove it entirely and rely on an inline filter), yer inline filter is restrictive if ya have one (paper elements don't like 2stroke oil, get a metal one), and last but prolly least some fuel petcocks are not quite right - for this and all the above (other than float level obv) ya can pull the line from the carb itself and drain the fuel into a clean container. Do it for a good long while, the stream should be strong and unwavering - if it isn't, that's the problem.

Odds are it's a starvation issue like ya suspected

[jerry aertker]

thanks for your input on engine cutting out - my friend who installed it mentioned the float not being upright - he said we could heat the flange and bend it - also the engine will not run without the choke partially on = also if someone knows of someone in the baton rouge area that would work on a skyhawk gt motor that would be good - cause I am ready to give up - thanks out there in the virtual world and merry xmas

[2door]

To adjust the float level you need only remove the float bowl, the cup shaped part on the bottom of the carburetor. The very small brass hinge like piece that the float pushes against is what needs to be bent, and only a very little bit. It will not require heat to bend. If, as I suspect, you're talking about the intake manifold instead of the float, if it is cast aluminum as some of them are, you cannot apply heat to it to bend, it will melt, and it won't bend but will break. If you're trying to level the carburetor and the manifold is steel you might be able to bend it but doubtful. How far off level is the carb? They will run just fine at a slight angle and do not need to be perfectly level. When riding at wide open throttle take note of the fuel line and watch to see if it remains full of fuel. If it does then the problem might be the float level. If it shows large air pockets, bubbles, then you're looking at a fuel flow problem from the tank. What spark plug gap are you running? Shoot for .024 to .028 for the best gap. Good luck, keep us posted on results.
Tom