Lets start with the basics. Compression. if good, rebuild the carbs. Then decarbon and replace plugs. Lots of things will "run" with no load. But if full of varnish, it's not getting enough fuel to run under load, and your high speed jets may be allowing to run wide open, while the low speed jets may be clogged.
However - BIG WARNING HERE - if you have badly varnished carbs, running WOT could fry the motor PDQ as you may be running too lean. If you really want to put the kibosh on possible varnish without tearing the things apart - then find some "mechanic in a bottle". Can be found at lowes. I had seen this stuff before, but never thought much of it - or any "snake oil" for that matter. However my brother recommended it, and told me to use it. -
Since he is the Chemist for VP Racing Fuel - I trust his judgement with regards to this, and I can say it REALLY works. Kinda spendy however. I would mix up a gallon, add oil, and then add the small bottle that treats up to 4 gallons, let run a few minutes, and shut down. Let sit overnight, and then run it again the next day a few minutes, maybe half the fuel... then run the rest out the day after that. Gives it some "soak" time to dissolve all the varnish.
I would only do this if I just could not do a physical carb rework, which is really the best option.
Linkage issue? Thats pretty easy to check to make sure the cam and roller are correctly positioned at idle, and the cam engages the roller as soon as you put it into gear and start to advance the throttle.
Blaine.
