I have a 1982 Maxim 650. The bike starts up easily and runs good, but I don't seem to have any top end power. Once the speedometer gets to about 70-75, it just wont' go any faster. This thing should easily top 100 mph. Not that I would want to, but I want it to run right too. I might be worth mentioning I weigh 225 lbs, but I would think it should handle that weight okay.

I've had the carbs professionally cleaned, acid cleaned the tank, new gas filters and gas, and new rubber intake boots. Compression is 125-135-134-135 across the cylinders, which I'm told is not bad for the age of the bike.

Any ideas on what the problem might be? I'm thinking either the valves need adjustment or maybe a bad diaphram in the carb, but wanted to get others insight. Thanks for any help.

Cary.

what do your plugs look like? Could be not so professional carb clean?floats set at wrong height? missing parts?first look at the plugs and go from there.

I'd also start cheap and easy with the plugs also.
I ride same bike and at same weight I have buried speedo and tach at same time.

You've said nothing about the history of the bike, did you just get it?
I'm leaning towards one or two main jets being clogged(even though they have been cleaned) that's about the end of the needle range and beginning of the main jet, but that's just my first guess.
Other than that, check your "choke" circuit. It's possible that the choke cable, or enrichining circuit may have something to do with flooding the top end, and fouling up the works.

has your bike got standered exhaust on it? if its like my 550 they are crap and restrict power, ive just bought a new grinder and im going to treat mine to a seeing to.. :P , i no the silencers unbolt so im on the look out for replacements :) ,
iv found you only need to rejet if they are straight through, i no some will disagree but i found binning the ones that came from the factory the best policy :ph43r:

Yup, maybe plugged up main jet. Could be running too rich, check you plugs for signs.