State of tune and top speed, '78 KZ1000

KZ Riders,
I want to see what you all think about this. All thoughts appreciated.

I love my 1978 KZ1000, but I'm not sure if I'm getting all I can out of it on the top end (top speed).

Here's the setup:

Stock engine, compression is a little low (120 psi on 1 and 4, 110 on 2 and 3).

K&N pods, Delkevic 4-1 with baffle removed.

Mikuni VM28 pumpers off an E1 Shaft. 22.5 pilots, 120 mains, air mixture screws 1 turn out, slide needles lifted (lifted by inverting the needle spacers, as these carbs did not come with are clip position needles).

Stock coils, stock points setup, with Wired George coil mod (line straight to coils from battery). Ignition timing is not advanced or retarded; it's pretty much set where the book says it should be.

15 tooth front sprocket, 33 tooth rear.

The bike runs great, runs strong. It tears away, up to about 90 mph pretty effortlessly. Handles fine, so I'm not worried about going fast.

My issue is that it seems to me like the bike seems to sort of top out at about 90-100 mph, unless you really push it. It seems to me that the bike should be able to break 100 without having to push it so hard. As it is, it seems like it would be a heavy lift to get it to 120, and that doesn't seem right to me.

I do plan on rebuilding the top end someday to improve compression, but don't have the time to do that right now. So, I thought I'd see if there's anything I can do, short of compression.

Is there anything you all think I can do, in terms of ignition timing or carb/exhaust setup that would improve top speed performance? I also have a set of Dyna coils I could put on it, if that would help.

What do you all think?

120 PSI = 8 Bar =  10 - 15 horse power drop is a way to low to get the power for top seed, should be 10 - 12 Bar = 140 - 170 PSI !!!

Your compression is on the low side but a Dyna 'S' ignition and coils will help with overall power and crisper running and i'd re jig the jetting with air correctors and a smaller main.
The 120 mains ,larger pilots and raised needles are losing you top end power and reducing your gas mileage.
Also are the valve clearances correctly adjusted to around 0.15mm and not running tight.
 

You can perform 100% (with parts and tuning) on the intake or exhaust side but destoys/waste the
expected power in the main core reaction power plant area!
You can have an unknown power bottle neck in every "perfect" system.

 

Stock in 1978... it would do 123mph at a 1/2 mile.
That may be with a 160lb rider though.

magazine.cycleworld.com/article/1978/5/1/kawasaki-kz1000

No baffle will cost you top end. 

You can't make optimal power without good compression. There is no quick fix.

The Dyna coils will make it run better but it will not be a noticeable HP difference, not one you can feel or see on the speedo. Advancing the timing will only make it run hotter and possibly cause damage.

Checking the valve clearances like Zed1015 suggested may up the compression IF they are tight (probably the most important to check)
As per the jetting people seem to always run on the rich side, check the plug color and adjust accordingly per previous suggestions.
Low compression engines don't burn fuel properly so trying to tune like that might be a loosing proposition.

Not much else to do except a ring/valve job.

There are lots of bikes out there running around with similar compression numbers. Its still fast enough to loose your license!
 

As Steve said, running with no baffle when the rest of the motor is pretty much stock will kill the top end. People need to get away from the idea that "noise = power" 

Wookie58 wrote:

As Steve said, running with no baffle when the rest of the motor is pretty much stock will kill the top end. People need to get away from the idea that "noise = power" 

That statement could cause an uprising amongst HD faithful

TexasKZ wrote:

Wookie58 wrote:

As Steve said, running with no baffle when the rest of the motor is pretty much stock will kill the top end. People need to get away from the idea that "noise = power" 

That statement could cause an uprising amongst HD faithful

Yeah most Harley guys have such loud exhaust they won't hear us pass them.     

With my competition baffle they try to get away from me. Sounds too good I guess.  As they try I drop down a gear and leave them in the dust. 
They ride too slow for me anyway.