Alf,
Thank you for your reply. Here is some discussion on your suggestions:
- Faulty fuel petcock or fuel pump/inappropriate fuel filter
The fuel petcock has not been rebuilt. But since I filled and drained the tank a few times, it seems to flow out fine. The '89 does not have a vacuum petcock, just on/off for removing and replacing the tank. The fuel pump is not stock, it is a Holley 12-426. It is rated at 25 gallons per hour. The fuel filter is stock, and is new. I replaced the old filter and lines when I brought the bike back to life.
- Poor spark. If everything is right, have you measured the coils voltage?. For experience I can tell that usually is around 9v when it must be 12v. Do the problem appear when the bike is hot?. Usually simply a bad connection wire/spark plug. I understand that not in your case, because on the dyno your bike works
I think there is a misunderstanding, probably from how I wrote my first post. I have never had it on a dyno. I was thinking a dyno would be an easier way to troubleshoot because you can run high power/high RPM with the bike standing still. I have not measured the coil voltage. I'll look at the schematic to see where to attach a sense lead, or if you can point me to it that would be helpful.
- Rich carb settings, hence my question about your mods. Or emulsion tubes being oval. Here the problem is the transition from low to high rpm: you open hard the throttle and the bike don't respond, being better a progressive throttle
I made a tool on the lathe to remove the emulsion tubes, so they came out nicely and were undamaged. Plus I did get them very clean. When I open hard the throttle, the bike responds very well. As the RPM increases somewhere up above 7000, that is when the miss occurs.
- Maybe lean settings in your bike? When transplanting your main jets, did you check that all of them were completely free ob obstructions? I've seen on a lot of years parked bikes that the jet inner passages are even blocked simply by its own rust, and no cleaning method is capable of unblocked the thing
I did go through the carbs and jets very thoroughly. It took me two tries to get the pilot jets clear. Initially I had bad low speed operation and used an IR thermometer to see that two of the cylinders were not firing at idle and low speed. I have cleaned a few carbs before, so I have some experience. Typically I hold the jets up towards a light and verify that I can see through all the passages. And, the bike runs great, except when that miss happens.
