Kaw Bench Racing!

The recent good discussion in ENGINES forum regarding horsepower gains has led me to do some thinking. This is often a scary thing... OK... the 903cc Z1 was supposed to have 83 HP according to Kaw. The 73 had a light crank, performance exhaust and performance oriented carbs. I work on carbs and there is a difference from one set to the next.

OK... for a sec, let's pretend that the early Z1 had 83 HP. My 79 KZ1000E1 ST is supposed to have 93 HP. How did they gain 10 HP? Wasn't the restrictive 4 into 2 pipes. Sure wasn't the puny #102.5 main jet pump carbs. Wasn't the heavier crank. Valves are the same size. Same spark plugs. There is a slightly different ignition curve. I would guess, if anything, the ST would make LESS peak horsepower than an early Z1. Perhaps a small bump in displacement? I can't imagine a 112cc bump with all the other issues yielding 10 more horsepower.

I suspect the marketing folks were helping to write the specs. I suspect the rear wheel horsepower on a good running ST to be about 65 HP or so; about the same as a good running Z1. I suspect the optimistic speedometer is part of the whole package! Last, why the heck did they drop the redline for the later KZs? From 9K to 8.5K using the same valve train. Strange.

Hmmm....Maybe different camshaft spec.s lift,duration,overlap,timing etc.

Post edited by: 1982KZ1100D1, at: 2007/12/28 14:43

Very good question. The hp also went up from the 78 1000 to the 79 1000 - even closer to each other than the 900/ST comparison. Doesn't make sense does it? I think you're right on when you mention "marketing".

Other factors to consider is fuel quality, EPA standards and how the power was rated. These are the variables that pop into my head. Also, in 73 I bet all test where done in Japan. Could the American market have done their own testing in Nebraska on the later KZ's? Americans love horsepower!! We will pay lot's for it.

I think it may have been done to fool the competion, tell all the people what you have and when they come out with a higher hp motor, you change your story to reflect what it really has and it dosent cost you anything.

My 80 KZ1000 was advertised as having 94hp if I remember correctly. It sat for 15 years and when I got it running it dynoed at 75 RWHP. That is without any tuning or tweaking, just got it running good and then into the dyno. I think 20 prior when it was new 94hp at the crank would have been very possible.

What's the usual drive line horse power loss percentage on a bike anyway (meaning difference between crank hp and hp to the wheels)? I know with cars the average loss with a rear wheel drive car is around 15%, just wondering what it would be with a chain driven bike?

Post edited by: HerrDeacon, at: 2007/12/28 22:44

Marketing Depts are still at it . The '06 Yamaha R6 was marketed as the highest revving production bike at 17,500 rpm . The tachs were off by 1000 rpm's . I think that the was some kind of legal action about it also . The '99-00 R6's that I roadraced showed a 15,500 redline , but hit the limiter at 14,800 on the dyno . Where by the way a stock one would never break 98-99 hp . 120 was Yamaha's claim , another marketing milestone "the first 200hp/liter" 600 or something . It's unlikely that there is a 20% drivetrain loss .

Since these HP figures are at the crank, chain/shaft or whatever makes no difference. The interesting thing is the upwards creep of HP ratings over the years. Fuel? Timing? Cam profiles? Can't imagine fuel making a horsepower difference and cam profiles are pretty much the same for all KZs. There was a swap in ignition curves from the original Z1... I think they actually changed the timing in 73 or 74 and the curve remained pretty much the same after that.

Must be a increase in PAPER HORSEPOWER:blink: :whistle: :silly:

My 'seat of the pants' dyno tells me that the new bikes today are stupid fast. Ever been on a Busa or ZX14? I did a roll on power wheelie (honestly didn't mean to) on a ZX14 while doing 30mph in 6th gear. Nasty nasty machine!!!