High Peter, no I have not yet found a fix. Thought I did but it came back again.
Yes, yours is identical to mine... right down to the last 1" of throttle being useless. For me, I can tell by ear the slight difference between what WOT sounded like before and what it sounds like now. At its best it sounds more high pitched at WOT and climbs 500' per minute better. At one point I changed the fuel filters, reco'd the fuel pump and the carbys, and cleaned out the fuel lines and replaced ALL fuel with fresh. (Used replaced fuel for lawn mower) I also did a few other minor things I cant recall at the minute, but it did seem to fix it for a while. Since then I done about 10 hours and it's back again. At the minute I am tolerating it as it will still climb at 800' per minute and tack off in my small strip. Now though I am having over heating problems and am wondering if the two are connected. I suspected a slight cold seizure but yesterday ruled that out with a end-scope inspection.
I did also purchase a Tiny Tack and it showed 100 rpm lower than my existing one, which was the opposite to what In was hoping. As I remember, I did a cable check and found the throttle was working properly with both carby cylinders reaching the highest point as it should do. The cylinders where also still moving up during that "useless" last inch of the throttle, so I ruled out the cable completely.
Tell me Peter... are you also having higher engine temps while the EGT's are normal?
Mike
