KZ650 Performance Question - Where's my power?

I have a '78 KZ650SR and I'm wondering about it's power, in particular it's quickness. Mine really doesn't feel very quick. Based on the numbers I see on the net, a stock SR had 62hp and do the quarter mile in the mid 13's. I know my bike is 30 years old and so it probably won't have those numbers but mine doesn't even feel like it's remotely close.

My car is probably a low 15 second car in the quarter mile and it feels soooo much faster than my KZ.

What could be robbing my bike of it's power? Or am I just not riding this bike the correct way to get the power out of it? I recently went for a ride with a '78 CB750 and it was way faster than mine. :S

It's not that I really want to go that fast anyway but I just worry that there may be something wrong with it that I'm just not picking up.

I checked compression and the numbers seem decent:
Dry:
#1 - 160
#2 - 160
#3 - 165
#4 - 170

Wet:
#1 - 170
#2 - 170
#3 - 170
#4 - 170

Also, my intake valves are a bit tight (I'll be fixing these this winter). Can these be affecting performance to this extent?

I have all the maintenace type things taken care of (i.e. carbs sync'd, coil mod, timing, etc).

Any ideas? I've only had this bike for one summer so I don't know the history, is there anything I should check over the winter. I have to reshim the intake valves and also replace the valve seals. Is there anything else I should look for while I'm in there?

Or do I just have too high expectations of my 30 year old bike?

Does it have stock size sprockets? If it was set up to cruise it would seem a bit slower

Are you running your bike up to the red line when going for it, peek power is at 8,500 rpm on a stock 650 and I spin my hot 650 up to 11,000 all the time. Of course I have cams and heavy duty valve springs a big bore, head work and a pipe Your power is in the upper rpm range.
Mark

Well, my 650C2 is a rocket....for what it is. Keep in mind it IS a 650, after all, and not a 750 or 900. As posted, you may have a gearing issue. Count your sprocket teeth and we can then see if you've got stock gearing or whatever.
Great compression, BTW, so if your intakes are a "little tight" they can't be out by much, IMO, with those compression numbers you listed.

Thanks guys, great points. I never thought of the sprockets. I just checked mine: 16T front and 42T rear. I don't know anything about these ratios, are these more for cruising?

Also, Mark brings up a good point. I'm not revving it real high. This is my first street bike and I'm more used to my cars lower rpm sound (my car redlines at 6500 and I usually shift at 5000). I don't think I've ever had the bike much over 6 grand. Just not used to the sound, and think it's time to shift. I'll try going higher.

So, if you were trying to accelerate quickly what RPM are you shifting? Do you do this in all gears, even first and second?

Thanks again.

The website www.gearingcommander.com covers ratio's and chain speeds on their website. Give them a try. and www.z1enterprises may be able to supply you with different sprockets if changing is what you want.

That's stock gearing. When going for a run bring it right up to the red line. These motors love to spin. I've missed shifts and pegged the tac with no ill effects.

with those compression numbers your getting i would say there is nothing wrong with your motor, do as an old french guy told me once[turn the throttle you sob] give that old girl some rpm. these old kawi's love the rpm remember the redline on your tach is just a suggestion. if you compare your bike to a car think of differance between solid lifters and hydralics.solid lifters will always rev harder than hydralics.

timebomb33 wrote:

with those compression numbers your getting i would say there is nothing wrong with your motor, do as an old frech guy told me once[turn the throttle you sob] give that old girl some rpm.

I hope that's all that's wrong with it. I think I'm being too much of a wimp. Just not used to high rpm sound. I just hope I can get a chance to give it a whirl before the winter.

Thanks guys.

Yeah I was out with a buddy who has a 400 seca. All night I was complaining to myself that my bike was too slow, tehn I realized I wasn't going past 5000RPM. So on the way home by myself, I revevd her up to 8 grand. It's a whole different world up that high.

Can't wait to try it now.

My tach says the redline is 9K, is this correct? The reason I ask is that I think the gauges on my bike may be from a different model (different topic ), so I just want to confirm what the redline is on an SR.

Don't compare a bigger car engine with a much smaller bike engine when it comes to revs. Mostly, what limits RPM is the weight of the piston and the stroke. My Mitsubishi 1.8 liters has a bore and stroke of 81mm x 89 mm (undersquare) and is redlined at 6,000 revs. My Zephyr 750 has 66mm x 54 mm (oversquare) and is redlined a 10,000 rpm. In other words, the much smaller ligther pistons plus the much less travel, allow much higher revs without inducing heavy pounding on the crank.