I need help with my throttle, possibly carb.

[dzdaz]

I just installed a 70cc engine on my bike and it was running great except for the throttle isn't working right. I unscrewed the cap where the cylinder and needle go in, pulled them out of the carb, then twisted the handle and it snapped back properly. The problem I seem to be having is everytime I put the brass cylinder with the needle back down into the carb then twist the throttle handle it doesn't snap back. The brass cylinder gets stuck at all the way open. Can anyone help me figure this out? How far down into the carb are the needle and cylinder supposed to go when you install them? I'm assuming they are supposed to slide up and down rather freely when using the throttle. Is that cylinder supposed to snap back down when when I let off the throttle? What am I doing wrong?

 

[Blaze]

Can you take some photos?

I had an engine that did the same thing. It was because the part that the brass cylinder slides inside of wasn't perfectly round. I took some pliers and gently squeezed it to make it perfectly round. Without anything hooked up, try sliding the brass cylinder in and out of the tube it goes into. If it sticks, you might have to adjust the tube to round it out a little better.

Also, remember that when the carb goes back together, the washer with the slot in it goes ON TOP of the E-clip on the throttle needle.

If that's not it, take some photos and it might help.

 

[gone_fishin]

there's a little slot down the side of the slide, look inside the carb-cylinder, there's a tiny brass knob sticking out, the slot should be lined up with it. when you have it right, the "large" angled notch should be lined up with the idle screw.

was that any help?

 

[chieflets]

yup make sure u slide ur barrel properly wit the notch in the cyclinder if not you may have also damaged it on your barrel should be slit

also some times i have found that unscrewing the barrel cap half turn does the trick too

Chieflets

 

[dzdaz]

Thanks everybody. I think blaze has the right answer. dax also suggested sanding the cylinder down a little.

 

[dzdaz]

It was the slide getting stuck. I sanded down the cylinder a little and it's working great. My engine is stalling when I pull the clutch in now tho. It won't stay running. I also noticed that the engine hardly begins to pick up until I get about the throttle about half way open. Is this just an idle adjustment issue? And can anyone explain the choke lever on the airbox?

 

[Blaze]

You may need to adjust your idle a little higher. You do this by adjusting the idle screw on the left side of the carb. Screw it in to increase your idle speed, screw it out to make it idle slower.

Don't expect it to idle perfectly before it's broken in. You may have to set your idle a little high just to keep it running.

As for the choke, the lever should only be moved up when you are trying to start a cold engine. As soon as you get it started you should be able to move the lever back down. Your bike might still run a little weak for a minute or two while it warms up.

One of my motors had a problem with the choke vibrating into the up/on position, which made it run rough. I solved this by getting a spring from a hardware store and running it from the choke lever to a screw on the carb. Make sure to use a very thin, weak spring- one that barely has any pull at all. That way your choke lever should be able to stay up against the weak force of the spring, but when you get your bike started and you move the choke lever down, the spring will not let the lever vibrate back into the up positition.

 

[Blaze]

Here is a picture of my choke spring installation. Note that the spring is made from very fine, weak wire. It works great.

 

[dzdaz]

cool

Thanks for the insight guys.

 

[azbill]

grit ?

the barrel of my new throttle was so tight I had to gently pry it out today Can someone tell me what grit I should use to smooth it up with ? I have some 1500 but suspect that would just polish it or is that the idea ?