Throttle stuck open?

[mohrbetter]

I recently aquired an 85' Honda Spree (NQ50) and cleaned the carbs, installed fuel filter, etc. I'm having a problem where it starts up but will go full throttle, without me touching the hand throttle. So I checked the cable and it works, it slides smoothly through the housing and i made sure i installed it the right way i believe with the long slide going against the key. But when it's installed there is no tension on the hand throttle its like theres nothing there. Any ideas are appreciated!

Thanks

[breaze]

Sure sounds like the slide isn't going down. Did you pull off the airbox connector, look inside the carb, and make sure the slide is going all the way down when the throttle is released?

[breaze]

The correct orientation of the slide is with the small ramped slot lining up with the throttle screw (this is an Aero carb but should serve for demo purposes):



When the throttle is released, the spring should push the slide down (view from airbox side down venturi):

[Wheelman-111]

Greetings:

Breaze takes very helpful pics plus he has admirable hand and fingernail hygiene.

He's quite correct in his description too. Let me add that the other side of the throttle slide - the one that's facing the inside of the scooter - has a little groove running its whole length. Inside the slide bore of the carb body, there's a little nub cast into the metal. This nub is supposed to engage the slide's groove. Normally the throttle slide should just drop to the bottom without any force or spring tension when all is as it should be.

A problem can arise when you - er, I mean some ham-fisted Previous Owner - tries to JAM the slide down without checking for correct orientation. With surprisingly little force, the little nub can shear off, and/or change the nice round shape of the bore somehow, so that the slide just sticks there. If that happens, there's no easy cure.

[Johnniespeed]

When a two stoke engine leans out, they can sometimes rev high giving the impression that the slide/ cable is stuck. Luckily this is only 49 cc and not 500cc.
Your description of no tension at the hand throttle however, sounds like the slide is sticking. Did you look at the carb inlet while twisting the throttle ? Does the slide fully drop ?