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I recently aquired a 1980 kz 750 4, it runs a1, pulls hard till the speedo pegs, somewhere around 80/85 it acts as if there is some sort of speed limiter, is there such a thing? The ignition system is oem except coils

Unless it's efi, no there's no govner/rev limiter. Start with the basics by checking valve clearances and adjusting as required, oil change, chain lubing, and a full strip and dip on the carbs with new o-rings. And be more specific with the bike. We need to know if it is all oem original or been bubba'd by the PO with pods and pipes.

The bike did not originally come with a speed limiter. However, based on the info in your signature someone has installed speed limiting devices on yours. They're called pods. Ed

The bike im talking about is a 1980 kz 750/810, open vh comp, airbox, two teeth bigger in rear, i do have comp baffle i have not tryed exceeding 90 mph with baffle installed

It probably isn't the battery, but I would test it w a digital multimeter to make sure it charges to a full 12.6+ VDC & check to make sure it holds a charge. Also, if it has the original coils, they may need replacing. Old spark plug wires can be problematic as well. And check & service the timing advancer.

Coils. A test you can do is to ride the bike at high speeds, then stop & feel the coils to see if they're getting hot to the touch --- press hard w your fingers. They should be warm, not hot. Mine were very hot, so I installed the green Dyna 3.0 ohm coils from Z1Enterprises.com.

Accell coils and wires, new plugs appear tad rich new batt and charging good, what i find strange is this happens exactly when the speedo hits the peg

Maybe it's not getting enough fuel at those speeds???

Take gas cap apart and ensure vent is not clogged...I would think that problem would manifest itself before that kinda speed, but it is easy to check, & cheap to fix.

Martin i believe u were right, i just got back from a well over 120 mph ride, can u guess what it was? All i did was install comp baffle into header. Aparently mains are too small for open exhaust. A little quieter than before but it accelerates quicker throughout entire rpm range

I dont know if i want to see where top speed is now, 130 or so is fast enough for a 34 yr old bike

Has anyone had an 810 topped out? What is the top speed?