kz 650 top speed stock motor?

I have a 700cc kit in my '80 650, with electronic ignition and a Kerker header. I live in ND and can end up in the middle of no where in about 10 minutes. I regularly run up to 100mph or so which is about 8500 rpm. I think my gears wind out about 120 which would be 10,500 rpm, not exactly sure because the few times I have done this I was not payning attention to the gauges. The front end developes a shimmy over 100, so I don't really like to run that hard very often. I am geared on the short side, however that makes it fun around town.

wheres the guy who did 145mph on the stock 750 ltd? :pinch: :woohoo:

My KZ650C wich did dual duty as drag and street bike would pull 12.8's all day at Great Lakes Dragway at over a hundo. Mods were a open Kerker 4-1, a dyna 3, one inch shorter forks from Frank's Forks, a one tooth larger rear sprocket, and K&N pods. The altitude density was about 500' (nice cool October day in the S. Wisconsin corn fields).

Before I moved to Colorado, I dropped in some KZ750 cams, angle milled and ported the heads plus did a re-ring. At an altitude density of 9000' I ran a very consistant 13.2, which would be around a 12.4 or less at sea level. This was all done with "stock" carbs.

120 mph should be no problem with a 650 with a 4-1, pods and and the correct tune.

I did well over 180 indicated one day on mine when she was bone stock, its more of a gearing issue on these bikes I would thing, the stock gearing is all about low down grunt. At 120km/h I'm at around 6000rpm on the highway.

wireman wrote: wheres the guy who did 145mph on the stock 750 ltd? :pinch: :woohoo:

cruising Louisville looking for a race. where's Milner?

The fastest stock Z650 I've seen tested made it to 195 kph when Moto Journale compared it to a Z1000. That particular 650 also cut a 12.8 in the 1/4-mile. When Motorrad made their first test, their bike made it to 193 kph. Both these had long straights where they could coax every kph out of the machines.

In mph, that's 121 and 120 mph respectively.

Personally, I doubt the 119 mph from the original CW test - it's likely a typo and should be 110 mph.

Now, the quickest stock Z650 I know to be tested did a 12.74 @ 103.32 in the hands of Big Bike magazine in 1977. They also tested the Denco tuned machine, the one used to set the world records, with wheeliebars and struts and a road racing slick and did 11.10 118.42! And at Bonneville, the same bike had earlier reached 141 mph. The engine survived about 150 drag strip passes and lots of Bonneville attempts without issues. It was only mildly modified; camshaft identical to Z1 drag cams, pistons from Denco taking it to 738cc, 10.6:1 compresssion, Denco CDI electronic ignition with 2 degree extra advance, Denco 29mm smoothbores, Denco 4-1 and Denco clutch springs. Stock clutch, stock head including valves.

Still, do not underestimate rider size and shape plus riding gear. Bike and rider weight has virtually zero influence on speed, the thing that counts is drag. Take a 100 kg/220 lb bloke in a flattering Aerostitch touring suit sitting upright while riding a bike with a worn out chain that's poorly lubed and adjusted with a little underinflated wheels - he will need over 50% more power do do the ton than a 50 kg/110 lb lass in a tight fitting leather suit riding prone on the same machine with a perfect chain and well inflated tyres.

I've had my totally stock KZ650-C1 at an indicated 120 mph on numerous occasions. Any speedometer may have a little bit of error in it, but I have run side by side with a couple different Dodges, a GTO, and a KZ750 and their speedos read the same. Faffi grossly underestimates the speed at 110 mph, that would not be a decent running KZ650. Here is a link to an un biased Cycle World road test done back in the day. They recorded the speed at 119 mph. There are numerous other road tests that rear the same if you care to look them up. No typos. Ed


articles.kz650.info/documents/KZ650%20Cy...World%20Roadtest.pdf

Nebr_Rex wrote:

wireman wrote: wheres the guy who did 145mph on the stock 750 ltd? :pinch: :woohoo:

cruising Louisville looking for a race. where's Milner?

Tell him to come back in the spring,im sure i can throw something together by then! :woohoo:

Don't know why I'm posting on a thread that some guy with 1 post started 4+ years ago.
But my 77 KZ650 custom brand new only ever got to 119 mph on the speedo , never could squeeze that last 1 mph out of her.

Got a lot of respect from my buddies on their 900's though, they couldn't shake me.

JD

650ed wrote: I've had my totally stock KZ650-C1 at an indicated 120 mph on numerous occasions. Any speedometer may have a little bit of error in it, but I have run side by side with a couple different Dodges, a GTO, and a KZ750 and their speedos read the same. Faffi grossly underestimates the speed at 110 mph, that would not be a decent running KZ650. Here is a link to an un biased Cycle World road test done back in the day. They recorded the speed at 119 mph. There are numerous other road tests that rear the same if you care to look them up. No typos. Ed


articles.kz650.info/documents/KZ650%20Cy...World%20Roadtest.pdf

I have the actual magazine and hence the test. The reason I'm sceptic about the listed top speed is that it did a 13.2 @ 98 mph whereas the KZ650SR tested a year later did a 13.4 @ 96 mph if memory serves, yet the latter topped out at 105 mph. And the KZ750 as well as the XJ750 both turned 12.4 @ 106 mph, yet topped out at 121 and 119 mph respectively. All tested by the same magazine. But the 119 mph of the original 650 could of course still be correct.

I don't have the article, but I have a few others and often the top speed was estimated, at least back then. The pdf looks to say "actual", though.

My 1982 KZ650 had badly pitted cylinder walls, poor compression, and used oil. It ran OK, but did not have much power. I never did a top speed run on flat ground. Recently, I replaced the cylinder block, sleeves and pistons from a 738cc motor. Running used but good piston rings and clean cylinder bores that still show the original cross hatching. Piston to bore clearance is .0013". Kept the 650 cylinder head, cams, etc., and used a standard thickness head gasket. Did some light porting of the heads. Am running stock exhaust, stock air box, and BS32 carbs, with one size larger main jets. My rear tire is one size over stock, or 140/90-16. The front countershaft sprocket is 14 tooth, whereas stock is 13. the rear sprocket is 33 teeth, which is stock. The bike runs considerably better than before.

I did a run yesterday on level ground with a light side wind. Since the 85 MPH speedometer is useless, I carried a GPS to record an true maximum speed. I weigh about 165. The effective gearing is higher than stock, (lower engine RPM for a given speed), due to the oversize rear tire, and the larger front sprocket. I tried running in 4th gear, but reached the redline, (9,500), and it would have gone more. Yikes! Shifted into 5th gear, and the bike topped out at 8,700 RPM.

Came back down to earth, stopped and read the GPS - Maximum speed was a true 117 MPH. Now I know this is a 738 cc motor, instead of 652, but it is far from perfect condition, and otherwise the engine IS a 650. I ran the numbers through "Gearing Commander" and it calculated that I would have been going 127.6 MPH. I know that is not correct. Perhaps the Primary Drive Ratio (2.550) I plugged in could be wrong, or maybe it gives speeds that are more like an actual speedometer might read. Anyway, I just thought this might be interesting data.