Quite a curious problem.

So when your in 5th pushing for 60mph and it slows down to 55 at wot can you hear the engine slow down as well?

I'd get a timing light to see if it ignition advances with rpm. Is it running smoothly at its top speed? Any misfiring?

speedingman wrote on 04/30/09 at 16:20:20:

This is exactly what I tell people to do to test whether or not they need a bigger main jet.
You've looked at everything else, why not the jets?

I'm a little confused about something here, so please straighten me out.  Am I correct in assuming that when you bought the bike, it had this problem, and after you replaced the carb with a brand new one, you still had the same problem...is that correct?

I read all your posts over and you said you replaced the sparkplug once already and the bike ran the same, and you said the old air filter was white and clean, and you said the fuel flows freely when you drained some out of the petcock.  Now you've replaced the plug with another new one, removed the air filter which was white and clean, and cleaned the petcock which you said was previously flowing freely, and the bike runs right.  Since it is running right, there is nothing wrong with the ignition system.   You did you replace the carb with a new one in an attempt to correct the problem you are having, and the new one made no difference.  Something isn't making sense here.  Your latest test run points to a mixture problem in the carb because the only new thing you did was to remove the air filter, which would compensate for an over-rich fuel mixture.  However, you've had 2 carbs on this bike and both acted the same.  It would be a real coincidence that both had the same mixture problem.

The plug that was in this bike was the one i put in when i bought the bike and was in there before the new carb was put on so it would make sense that that plug was ethier faulty from the start or was fouled out from the old carb and i never thought to replace it intill now it had only been in ther for a 100 miles or so befor i changed carbs and head gasket and so forth. so all this fustration could have very well just been from that spark plug. Sorry for the confusion.

My wife said something about the plug way back, but why would i listen to her, that soesnt't make sense to me... well i guess i learned a lesson through all of this, Listen to your wives they could be right. It been 8 years now would have figured that out by now right?