Tornado
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- Joined
- Dec 5, 2017
- Messages
- 4,982

If you have a blockage in the slow running jets, you might have the throttle stop wound up too high in order to get the motor to idle. The slide should hit bottom with all the slow running jets working. If it doesn't do that the idle might be irregular or unreliable. I don't think your problem has anything to do with the needle position. That usually only does it's thing above a quarter throttle. Below that, it is the slow running jets which work. When you wind the idle mixture screw in, if it is a fuel adjustment, you should be able to cause the motor to miss - then back it off slightly so it idles smoothly. If the slow running jets are blocked, you probably won't get that response.
Mixture adjustment does have the effect you describe...starting out as 1.5 turns from fully in, I can wind it out (leaner) and get changes in idle until it gets lumpy. Can also wind it in 1/2-3/4 turn from 1.5 out and get rougher idle. So seems like idle circuit is flowing.
So to summarize, engine rpm stays high from immediate throttle slide closing for 2-3 seconds. Confirmed slide is moving freely & fully closing with the grip twist...not a cable hang up.
For rpm to remain high, does that mean too much air being sucked in? Mani to head bolts are good and tight (were locktited in last season). Carb to mani sealed with fresh permatex grey today. Could there be leakage around the slide, like with a worn out bore? Could the choke slide have a role there? What about possible timing issue...say the EI stator plate has become loose and rotated to incorrect position...would that account for what's happening?