Russ I'm not saying what is wrong yet. We do need to get info to give you a good guess. So that is what we are doing. You will be the one who finds the problem with our help.
1. If it spins nice it means the "motor" is probably good.
2. If it does not make a noise, like teeth slipping on teeth, let us know that.
3. If it truly just spins, Do this: WITH BATTERY NEGATIVE CABLE DISCONNETED, get under the hood and operate the foot lever and watch what is happening or not happening. Maybe it's just the linkage. The levers can have worn pivots or broken or springs missing. Something like that. The pinion gear is supposed to press against the flywheel just before motor spins. Then it's forced to engage. So your test may show the pinion gear pressing against F/W or if teeth are aligned, it will mesh with flywheel teeth.
4. If it looks like it is mechanically "tight" and is engaging, then next test is with battery connected. That needs some safety measures. Report the static test first.
5. As said you could have worn teeth but I would think it would have made a loud noise. Not just a spin noise. Please advise.
6. As Kevinski said, it very well could be the bendix/clutch. The piece between the spring and the pinion gear. That would appear as the pinion engaging flywheel but pinion not spinning, gears not slipping but clutch slipping, one half of the clutch turning and the other half not. The whole bendix is available for $25. "Fun" project.
Take off the negative battery cable until we figure out your other issue. Which is the starter/ignition wiring.
Here are the question for that issue.
1. Do you have a ballast resistor? Show us it's wiring.
2. Tell us exactly where the two smaller wires on the starter mounted switch are going.
3. Are there any other wire on that switch other than those two and the battery cable? Am I right that they are all on the switch battery stud?
4. Confirm you have a 12V battery. Who did the 12V conversion and when?
