Ok, maybe it’s not that bad. One step forward, 1.273 steps back…

As suggested by a XJ-lister with MegaSquirt experience, I set about reinstalling the butterflies for the subthrottles, the intent being to set them to restrict the air intake. My theory, verified by his experience, seems to indicate that my throttle bodies are probably way too big for this engine. The butterflies restricting the overall air flow into the engine may serve to widen the throttle range a bit. I fear the only real option will be to change them out for smaller unit or perhaps build a manifold to let me use only two of them. Much remains to be discovered, but I need to start somewhere.

I removed the air filters and was able to reinstall two of the butterflies without difficulty. Of course, the first one I tried on the “dark” side of the bike (the side away from the lighting in my workspace) crossthreaded and twisted in half in the removal attempt. After warming the area with some rather colorful language, I removed the throttle bodies, drilled out the broken screw, installed the two remaining butterflies, LockTite’d all of them and finally secured the assembly at the recommended 9 degrees from open.

I reinstalled the throttle bodies and started the bike up, only to find that now the throttle doesn’t close against the stop. I can gently force it against the stop, but it springs back open, reving high the whole time. The only thing that comes to mind is that maybe when I put thread lock on the screws, a drop fell in on one of the throttle butterflies, dried there and is now holding them open. I suspect it will be #3 because it seems like it’s always #3.

Well, with the bike trying to idle at it’s maximum attainable RPM of about 3800, the air restriction does not appear to have been too much. The advance is still crazy up there and it surges like it’s hitting a rev limiter, but at this point, I have done no adjustments to the ECU, just added the subthrottle butterflies back into the intake tract. That, and broken it such that the throttle is cracked open pretty much permanently.

Just this moment, I’m far too frustrated to safely pull the throttle bodies back out to troubleshoot the stuck open issue, so I will call it a night.