In my previous post - described how 500 will not get to high rpm. If you try to rev it (even with no load), then at about 3000RPM - it stumbles and loses rpm, then will increase rpm up and down - never staying at high rpm. Suggestions were: ignition - I replaced points , condenser, cap, rotor, static and dynamic timing set. - no effect. Another suggestion was float level low - removed and checked - OK also plenty fuel in bowl so I doubt that pump is bad. No effect.

I am out of ideas. Any other ideas?

Hi Martin

I think the reason nobody is responding is that unfortunately, this kind of symptom is very common in 500 and 126 engines, and can be caused by a myriad of things.

Tricky bit is discovering which one in particular is causing your problem.

It can be very time consuming and extremely frustrating.

Do you know any other owners locally you could get together with, and swap bits by a process of elimination?

I believe that you are right about that. I do not yet have anyone that specifically knows 500s, but between my own experience and some friends we are working through it. I have eliminated some of the easier possibilities and now I am into the more tricky ones i.e. valve train, subtle carb issues. I would like to solve it, but I don't have a specific timeline that I need to meet so I am not frustrated. I know that they are very simple machines so it should be solvable. Thanks for you input.