random revving ???????

[jackbmx2010]

hey guys, ive had this problem for a while now with my 70cc but it is getting pretty bad recently. when i rev the bike it goes but when i get off the throttle it doesnt go back to idle and the revs slowly keep building up. I have run it with the air filter off and i can see the slide is going back down so what else could cause this ? valve clearances are ok and so is timing. new piston and rigns have had about 5 hrs riding total. im stumped

 

[BananaMan]

i had a similar problem and found it was an air leak between the carby and manifold.

check all your gaskets, hope this helps.

 

[Nuts 4 50s]

I had the same problem.

Make sure you have some free play in your cable.

Also if you have a plastic throttle, pull it appart and check for catch points on your throttle tube guides. What happens is that when you twist the throttle it can catch on the throttle casing on the way down. This can be easily fixed by using a file and carefully taking the catching edge of the throttle tube.

This will help as the tube can now be snapped back into the idle position and not get stuck on anything.

Hope this helps.
If its not this problem then i dont know what else it could be.

 

[jackbmx2010]

thanks guys. I have had both of these problems in the past so it will probably be the same happening again. thanks

 

[Nuts 4 50s]

thanks guys. I have had both of these problems in the past so it will probably be the same happening again. thanks

No probs tell us how you go with it.