KZ550 vs KZ650 questions

Having been massively, positively impressed with the build quality and, just as importantly, the brilliant execution of the bikes construction, I am contemplating adding a 550 (standard) to the stable to replace the VT500 Ascot I keep for rainey days.

Now, for those in the know, is the 550 just as fine a design, as well put together, as easy to work on?

The 550 is an easy bike to work on. The top end comes off in-frame but if it has been maintained properly and not abused heavily you will likely never have to touch anything on the engine. A bulletproof bike in their day; probably moreso than the 900. I still miss my old GPz 550 but keep telling myself it is just romantic memories.

Thanks, GypZee. I know it's always been proclaimed bullet proof, but when Motorcyclist magazine did a touring comparo back in 1981, they claimed the KZ550 lost power towards the end and it used quite a bit of oil. And Joe Minton did an article for the same magazine, upgrading a used KZ550, and it needed new oversize pistons and a full valve job. OTOH, Keith Code used them at his school and said they could not be brought down.

Now, I just mention this as a curiosity since I do not fear the mechanical aspects. I just wondered if it was as intelligently made as the 650, which is generally a dream to work on.

The 550's were designed very similarly to the 650's, but just smaller and lighter. They got a few upgrades over the 650, though, like they all got Hyvo camchains from the start. And I don't think I've ever seen a thread on here about a 550 starter clutch, so for their size, I think the starter clutch is better than the 650. They were all 6 speeds. I think all 550's had tubeless wheels, whereas the 650 wheels, even though they look similar, use tube wheels.

They use the same valve shims as the 650, so you can share shims if needed.

The 1980 KZ550A used points and 1-phase charge systems. All others got electronic ignition and 3-phase charge systems.

The gpz550's amped up the performance.

The early carbs are very simple, mechanical slide carbs. Very easy to work on and in my opinion, are made better than the Mikuni's in terms of castings and machining. However they do have a tricky choke system that sometimes lose choke flaps. That comes down to an inspection/maintenance issue, but they are easily removed and inspected without removing the carbs form the motor.

More good info, thanks!

I just re-read a comparo between the Pantah 500, CX500, KZ550, GPz550, GS550M and XJ550 Seca. Not going into detail, but the GPz was 6 mph faster than the KZ, 0-60 mph was idenitcal but the KZ was much quicker during roll-on tests in the top 3 gears.

loudhvx gave better detail than I could have, but it makes sense that when Kaw did the 550 they improved upon what they learned from the 650. the GPz (at least in 82-up) had a little bigger cams and larger CV carbs than the KZ(not sure if the later KZ's might have shared the CV carbs) and earlier GPz which would explain the performance difference.

My GPz had a Moriwaki ported head (would kill for that today) , both Bassani and Yosh headers (pre and post crash :whistle: ) Fox rear shock, corbin seat, and superbike bars for class racing. Bought used for the paltry sum of $500 in 1985 money. Sure coulda used a 600 kit and some cams though...

Did you also upgrade the chassis, or just the engine?

There are a lot of versions of the 500/550 four. These are the ones I can recall, but I'm bound to have missed some:

1979: Z500, triple discs
1980: Z550, triple discs
1980: KZ550, single disc/drum
1980: Z550LTD, double disc/drum, adjustable suspension, 16 in rear wheel
1980: KZ550LTD, single disc/drum, adjustable suspension, 16 in rear wheel
1981: GPz550, triple discs, adjustable suspension, headlamp fairing
1982: GPz550, triple discs, adjustable suspension, UniTrak rear suspension, headlamp fairing
1983: KZ550A, single disc/drum, adjustable suspension
1983: Z550F, double disc/drum, adjustable suspension, UniTrak rear suspension (1982 GPz chassis)
1983: GT550, double disc/drum, adjustable suspension, shaft final drive
1983: Spectre 550, single disc/drum, adjustable suspension, shaft final drive, 16 in rear wheel
1984: 550LTD, single disc/drum, adjustable suspension, shaft final drive, 16 in rear wheel
1984: GPz550, triple discs, adjustable suspension, UniTrak rear suspension, half fairing, 18 in front wheel

My favourite out of these would the the 550A, what with its single disc/drum brakes and upgraded suspension while retaining normal instruments and twin shocks.

Had my first 82'Gs550L at 16. road it a Hole summer $300 bucks guy couldnt get it running- cleaned the carbs LOL had a Terrible COLD start issue- had to pop start it everywhere, it seemed when hot start right up, if ur lucky lol- Hated the rainl didnt want to run, but still got me to work everyday during the summer!~

i have been told, the 450 was just as nasty but way better gas milage- WITH less carbs(2)-

650's were always the next step of a good, fast bike- Def.always keepn' with the 9's an 1000's on whindy roads, if you can hold S'...

loved the 550L tho 6 speed with awesome guages, good bobber~

I remeber 11pm, 20 mile trip...in the woods of Pennsylvania~ broke my throttle PULL Cable!
LOl instead of even coming to a stop- to swap out the push to pull cable, i just reach under my tank~ throw away the plastic, when i ripp the cable out an just SUICIED shifter like "PULL throttle" the rest of the way HAULN' ASS. FASTEST That bike had Ever ripped LOL just crazy times-

but all around good bike~ chain ended up braking throw out the hole tranny- chain got stuff in the sprocket never ran again lol~~

I've owned a GS550E as well as a GS650 Low Slinger and neither were as good as the Z650. 550E is most similar to the 650B1 and its engine was extremely peaky, seat hard, cornering clearance limited and engine vibrations numbing. Handling was heavy but predictable, though, and triple disc brakes good.

The 650 had more low-end power than my Zed, but a big whole in the power around 4500-6000 rpm. And vibrations above 4500 quickly numbed hands. Seat was thinly padded and, like any cruiser, forcing one into one position only. Handling was horrible despite efforts to stiffen the fork and fitting KONI shock absorbers. Fork would bottom and front wheel lock early, making it impossible to take full advantage of the strong front brake.

Neither were as easy to wrench on as the Z650 and neither were as well made.

But we're way off topic now