"Fine tuning" the 650

Great news, I have my XJ firing on all cylinders!

Here's my previous thread.

I wet set the float heights and found #2 too high AND #1 too high (wasn't as bad as #2). Also I was inspecting the throttle shaft and valves and I noticed they didn't return to the closed position smoothly. I swapped butterfly valves on #1 and #4 based on a visual hunch and boy that made a big difference. When I first rebuilt the carbs to replace the throttle shaft seals years ago, I didn't keep track of the butterfly valves, doh.

Ok now for some questions on the "fine" tuning of this magnificent machine. I have it idling smoothly, no more jumping and sticking to 3000rpm and no more dying. But even though it idles nicely I have the idle adjustment screw backed all the way off, but still it will idle at 1,500 rpm. (The throttle cable is not keeping it open either) Also, I have to give it throttle when initially starting it. That isn't standard is it?

With the vacuum sync, I have each cylinder really close to each other on the gauge, but I didn't have to adjust hardly at all. I'm talking a quarter turn on 2 carbs. I'm think my yics tool is blocking ok. Does that sound right?

 

2 things to "worry" about - -

Did you get your butterflies centered "perfectly" when re-installing, after your new throttle shaft seals?? (suspect a leak or mis-alignment here)

Did you completely clean your Pilot system, including the 2 little transfer ports near the Butterflies?? (suspect blockage)

You're getting air in somehow - - find it !!

 

No throttle should be needed at start - either enrichment if cold, or push start if warm.

Didn't go back to the old thread, but did you WELL-OIL the movement on the butterflies - those hinges and springs could be hanging, or there might be crud where its supposed to land closed at idle? Mine had that

Sounds like your butterflies are open a little too much at rest, or you're too lean, or both

 

When I got mine balanced out right and the intake air leaks corrected, it would start instantly when you pushed the button, just fire to life, no throttle.

And was consistently getting 45-55 mpg.

I mention it a lot I know, but those gaskets between the head and the carb boots break down and go to hell and suck all kinds of air. That was the bulk of the problem with mine, not the carbs at all.