What to add to the kz900 to get that extra umph?

I have a 1976 kz900 A4 with 40,000 miles on it. I always browse through eBay to see what kind of new parts they have. Well I got to thinking, I always see "drag bike" next to the parts title. Why not do something to my bike to give it some more power like these drag bikes, but nothing too much where the engine will tear itself apart after every couple of rides. So my question would be, what can I do to my bike to give it some more power without having to major engine rebuild. I don't mind taking the engine apart, just nothing like over sizing the cylinders. Something more the lines of getting a performance cam or crank. And could you also tell me specifically which one to get and what the benefits would be? I would greatly appreciate it.

Sean P

Vacaville, CA

Before considering modifications you probably should start by putting the bike on a dyno to see if it is currently making the power a stock bike should make. That would help in a couple ways.

- If you find the bike is not making as much power as a stock KZ900 should make you can look into tuning it so that it does. Once properly tuned it may satisfy your desire for more power.

- If you find the bike already is making as much power as a stock KZ900 should make you can use the dyno sheet as a benchmark from which to measure the effect of any modifications you make. So if you make a change and make another dyno run you can see if the change actually helped performance and by how much, or you might find that the change actually hurt performance. By establishing a benchmark you take the guesswork out of the effect of modifications. Ed

40,000 miles on a 40 year engine. Spend lots of money :woohoo: :woohoo:
Start with a set of drop in cams $250; that's used
Valve job, guides, HD springs, clean up the intake ports $750
All new liska cam idlers, rollers, gears with new HD cam chain $250, which means you still have to split the cases. Which opens up a can of worms. Then you'll check the crank, want to weld it. Put a flat HD plate on a milled main bearing cap. $250.
4 into 1 header $250 used
Good Dyna ignition & coils & wires $250
Dyna rev limiter $150
Then of course your $500 -$700 used carbs
Then, Barnett clutch plates & HD clutch springs, weld the rivets in the basket, $250
Tranny? HD 2nd output gear $120. an overshift bushing $15
Then that 130 x 18 rear tire will spin like it's on ice
Had enough? Of course, your doing all the labor! :woohoo: :woohoo:

OR: You can just tune it up with a Dyna set up.
Clean carbs.
And change to a 14 tooth countershaft sprocket, up the back sprocket to 37.
And when you twist the throttle, You'll think you just spent all of the above.
Won't be good for a highway trip, but in town you can show off with your quick & old classic.

Or: wake up in the morning, have a coffee, wake & bake with some California green & sticky, go out and wipe off the dew from the seat and start it up and go cruisin! with a smile on your face & money in your pocket

Fair and balanced? You decide!

Lose ten pounds then your bike will be faster. Much cheaper. Might be eating cheap after paying all the go fast bills anyhow :laugh:

z1kzonly wrote: 40,000 miles on a 40 year engine. Spend lots of money :woohoo: :woohoo:
Start with a set of drop in cams $250; that's used
Valve job, guides, HD springs, clean up the intake ports $750
All new liska cam idlers, rollers, gears with new HD cam chain $250, which means you still have to split the cases. Which opens up a can of worms. Then you'll check the crank, want to weld it. Put a flat HD plate on a milled main bearing cap. $250.
4 into 1 header $250 used
Good Dyna ignition & coils & wires $250
Dyna rev limiter $150
Then of course your $500 -$700 used carbs
Then, Barnett clutch plates & HD clutch springs, weld the rivets in the basket, $250
Tranny? HD 2nd output gear $120. an overshift bushing $15
Then that 130 x 18 rear tire will spin like it's on ice
Had enough? Of course, your doing all the labor! :woohoo: :woohoo:

OR: You can just tune it up with a Dyna set up.
Clean carbs.
And change to a 14 tooth countershaft sprocket, up the back sprocket to 37.
And when you twist the throttle, You'll think you just spent all of the above.
Won't be good for a highway trip, but in town you can show off with your quick & old classic.

Or: wake up in the morning, have a coffee, wake & bake with some California green & sticky, go out and wipe off the dew from the seat and start it up and go cruisin! with a smile on your face & money in your pocket

Fair and balanced? You decide!

Id change just a couple of things:
Find a good factory electronic ignition and coils,used of course.
Forget the rev limiter,unless you live at the track. :lol:
Put a set of $150.00 28mm pumper carbs on it from a 79-80 1000.
Check the stock clutch plates/springs,If theyre worn replace them with another set of stockers.
Leave the stock trans alone,forget the hd 2nd gear and overshift bushing unless you live on a track with an air shifter.(somebody spends too much time on apes website! :woohoo: )

Just came back from a ride to the ocean. It was freezing there, any way I just a tune up on it so it's running pretty strong. It definitely isn't lacking any of the power it should have. But I just figured giving it a couple more horses ( about 20, give or take) it would just make it that much more fun to ride. Don't get me wrong that thing is a blast to ride and so darn nimble it's hard to believe it.

650ed- You make a valid point, for putting it on a dyno does it have to be specialized for motorcycles? Or can it also be a car one?

Z1kzonly- Yeah I'm not planning on spending that much money on it. Putting the cams and rollers and gears in there sounds pretty doable and something to look into. For the crank, would it be worth it to do something with? Getting that clutch would be nice, can never have go wrong with a better clutch.

Wireman- what would the different carbs do? The ones I have are 28mm stock carbs. And yeah I won't be doing any track days, just playing on this side of the country.

IMO I would make sure it is running like it should. My 76 kz900 runs extremly well for its age. Mine has 11,000 mi though so it's probably alittle stronger running than yours. My up grades include - kerker header- dyna & accel ignition - carbs professionally rebuilt,tuned,sync'd - pods. It pretty dam quick I'm doing 100 mph pretty fast when I'm getting on it through the gears. Plenty fast for me. Like Ed said make sure it's running like it should before you start upgrades. Just my thoughts. Here's a pic for ya.....

1976KZ900 wrote: Just came back from a ride to the ocean. It was freezing there, any way I just a tune up on it so it's running pretty strong. It definitely isn't lacking any of the power it should have. But I just figured giving it a couple more horses ( about 20, give or take) it would just make it that much more fun to ride. Don't get me wrong that thing is a blast to ride and so darn nimble it's hard to believe it.

650ed- You make a valid point, for putting it on a dyno does it have to be specialized for motorcycles? Or can it also be a car one?

Z1kzonly- Yeah I'm not planning on spending that much money on it. Putting the cams and rollers and gears in there sounds pretty doable and something to look into. For the crank, would it be worth it to do something with? Getting that clutch would be nice, can never have go wrong with a better clutch.

Wireman- what would the different carbs do? The ones I have are 28mm stock carbs. And yeah I won't be doing any track days, just playing on this side of the country.

Stock carbs on a 76 900 are 26mm,unless they've been changed out.

Use a place that has a motorcycle dyno (see video below). Ask around the local motorcycle shops; someone ther should be able to make a recommendation for one in your area. Ed

# 1. HEAD WORK, so underrated but tons of performance to be found. Get the head right, you wont be disappointed.

Mild to med port work with valve job.
Used set of VM 28's pumpers if possible
Electronic ignition - Factory or Dyna
Header
Pods

This will give you the umph you are looking for.

These bikes can really nickel and dime your ass. Nothing cheap about upgrades, always seem to find ways to bleed money.

With 40,000 miles, would worry about cam chain and cam gear.

Restore your bike and buy a used R1 for your power fix

These old engines are an expensive game to get into I'm finding out.

The biggest power adder would be 31mm bs34s from an 80 or newer kz1000.
The same price as 28's and a while lot more balls. Cams can be degreed to 105lc for 4 to 5 hp
for even more umph.. If your clutch slips clean the plates and re-install if it works run it A 1015cc
or 1075cc piston kit that nets 180 psi would by itself be a huge power increase.