Motorcycle Repair: ct70 air fuel mixture, air fuel mixture, flywheel engine

Question
I just got a CT70 for the kids, I cleaned the carb, and now am having problems with setting the idle/air screws. The bike now runs wonderfully in 2nd and 3rd. But in 1st it is vibrating and reving like crazy, I have never had a bike before...this is very frustrating...please help!

Answer
Betty, You didn't say what year model the CT70 is. They have been making them since 1970... here is a sample of the parts listing illustrations. Carb section shows a round and rectangular float bowl option.

Because I don't know the year I don't know if it has CDI ignition (non-adjustable) or the old-fashioned points/condenser (adjustable). If non-adjustable, then you can move onto other troubleshooting steps.....  

The valves need to be adjusted to .002" cold in/exhaust on the compression stroke.
Check the intake manifold/carb connections for any air leaks.
If you cleaned out all the jets and installed them carefully, then you can focus on the two adjusting screws.

The screw that is centered in the middle of the carburetor slide bore is the speed screw. The one that is more forward with a blunt end which modulates air/fuel mixture at idle. Idle mixture screws are set about 1 3/8 to 1 3/4 turns out from being gently seated into the carb body. Use that to begin with, warm up the engine and let it idle, if too fast turn out the idle mixture screws until it slows down to around 1200 rpms or a comfortable speed where it won't start to take off on you, until you actually turn the throttle.

There is also a clutch adjustment on the right side crankcase cover. If the clutch is sticking due to sitting for a long time, then any attempts to adjust it will be fruitless.

http://www.minitrail70.com/owners-manual/ct70-trail70-owners-manual-37-46.html

If you have an older model with points/magneto, then the points need to be adjusted through the slots on the flywheel, so that they just OPEN at the F mark alignment on the flywheel/engine case.

I hope this is somewhat helpful for you... Please be very specific about make/model and year when you are asking questions here.

Bill Silver