Hi Flypeter, hehe, my `79 did that for a while. It would pull strong as a diesel (any gear) until 5500-6500 then just FLATLINE!! LOL Check your floats (float movement/levels) & jets for varnish inside. If thats no good, TOTALLY strip the carbs,flush´em and blow out ALL jet passages.(torch files work great for that) Honda´s are NOTORIOUS for not runnin worth a crap without the breather. They need the long run (intakes)to make enough vacuum for the CV´s to operate right.Check the CV´s for ANY oxide too,that´ll cause intermitent choke-outs too. K, finally, I found out a hidden problem with the vulcanization of the intake rubber to the aluminum intake runners. I slit mine off because I run clear (gas line tubing)tubing from my carbs to the intake. I found 16 very oxided leaks that NO visual inspection could find. I know the carbs are a major pain to get in/out with stock rubbers, the clear tubing (available Rona,Home depot..)solves that problem very well. I´d also check your intake O-rings too..(intake to cylinder) A lil gasket glue could fix it for ya. I guess, also check the seal to the air box. I hope this helps ya out, if not, tag me back and I´ll maybe have a better idea of whats going on after you try some/all of the above..OH! and P.S) Do a compression check...I had a `86 CX go goofy like that from a BARELY blown head gasket..Look for wet deposits on A/both plugs, or oil in the antifreeze. ;D GOOD luck! ~The Ghettoman...