JDX8 timing symptoms

[kiedro44]

I've set the points and attempted timing the motor on my 73' X8. It runs strong from about 4000 RPMS and up according to the tach. Below that she misses a lot (I can see at the exhaust ports that she's not detonating consistently)and then dies. In other words, "idle" seems to be at about 4000 rpms. Does this ring a bell with anyone as a symptom of incorrrect timing? Or maybe something else?
Thanks.

[400brian]

The thing I would try first is to lean the idle mix. That's the screw on the left hand side of the carb as you are sitting on it. The '73 X8s were especially known for this.

It's easier to get at if you remove the clutch cover of the engine cowling. The air box is in the way coming down from the top.

See if screwing the needle in a 1/4 turn or so helps. The main screw on top is the high speed, and at idle that screw has no effect.

If the sled idles better cold than hot, that would tend to support my recommendation.

[lwb140]

i agree w/rian sounds fuel related for sure , if it was a cdi machine that woould be a different story could be a rich or lean mixture down low causing the issues wade

[400brian]

BTW, has this carb been cleaned and / or rebuilt? It's possible you could have idle passages plugged.

[kiedro44]

Well, I adjusted the low speed needle on the Walbro and it helped only a little. So I swapped to a Mikuni set up and ran it. I did get it to idle down to about 2500 RPMs but it still seems spotty and jumpy. It'll sit at 2500 and then snap up to 2800,then climb up to 3000, then drop to 2500 and run there a minute or two, etc. Keep in mind I'm test running this motor in the sled with the clutch off, with all new seals and gaskets. I'd say its acting like its sucking air in somewhere to make RPMS fluctuate but it happens so quick (again, it's "jumpy") that it seems like only a snafu of the electrical sort would make it run that way. Do I have a short somewhere? I think I'm going to replace the other condenser too and put on a new pair of plug wires to see if that helps make it run smoother. I've already replaced the external coils. Any other ideas?
By the way, which direction turn of the stator plate advances the timing, CW or CCW?
Thanks

[lwb140]

ccw will advance it or opposite the direction the engine rotates , could be your timing advance weights coulding issue , but clearly your carb is issueous if the sled runs with a mikuni on it , do you plan to leave it on there or put the stock one back on ? it would be dumb luck that the mikuni is jetted properly for the 400 , i tend to think your problems are fuel related if youve just pit new seals in it and you have no obvious vacuum leaks , you can buy ignition testers on the cheap at autozone or someplace similar that go inline that allow you to watch the spark , you can run the engine with them inline and see if youve got an intermitten problem or issue wade