Dead spot in throttle curve

[Doug in San Diego]

Hello all

I have a dead spot in my throttle curve. If I am cruising at say 35 mph, then hit it, it will bog for a second then accelerate fine.

From a dead stop, I get a slight bog when I first twist the throttle.

I can actually find the "hole" if I just cruise at say 5mph and hold the throttle at about 10%

If I hold it at 10%, I can actually make the engine die.

I just set the Idle screw to 2 1/2 turns . It was at 4 1/2 (will see if that fixed it)
Fuel filter clean
Fuel line straight no dips
Vacuum lines good
Wires tight

I have read many threads with this similar problem. I was wondering if you have determined what causes this problem.
Is it always the same thing, or is it one of five possible things?

My next check would be the valves

Doug

Ps sorry for not checking my own solution(mixture screw) I just ran out of daylight
If my problem was solved by this, I will let you know

[Rebel]

Yeah check the valves, you might be running a little lean as well. Try checkong the needle valve and if it is adjustable lower the click a notch and see if that helps.

[jmkjr72]

I would also look at your contra spring and tbe rear sheave
When you look at the rear pulley you want to look at the angle of the pin slot if it's not a nice linear slot it will give you a flat spot
Also the rear spring if soft will collapse too fast and you will lug for a bit around mid throttle to overcome it

[kz1000st]

Spray WD-40 on your intake manifold Doug. You might have a crack or leak there. If you do the idle will pick up for a few moments as the lean condition is overcome.

I had the same condition on my 150cc and the manifold was cracking.