1976 1015 with APE 410 cams hp and tuning info

It's been months in the making because I don't have a huge budget and sometimes things get halted while waiting for the cash to get the next part. I'm still not done yet but 1 or 2 more Dyno runs and it should be.

I bought a 1976 KZ900 that wasn't running right and it turned out to be the PO put in new rings but did not hone the Cylinders correctly so it had low compression. I could have just honed the cylinders and got new rings but I am not that kind of guy. Instead I decided to pump it up a little.

After some researching and price checking I sent the cylinders and head to Pitstop Performance. Joe went over the valves, cleaned up the ports a little, dropped in some APE 410 cams and bored the cylinders for the MTC 1015 pistons.

I got the top end back together and all the gaskets leaked, still don't know why but the second attempt was successful. The bike ran pretty shitty with the stock carbs sucking air through pod filters and the 4into1 Motogpwerks race pipe so I started messing with jet sizes.

I settled on a 17 pilot and 120 mains and the needle in the center position. The bike ran pretty good but was lean on top and I could tell it was short some hp. That was early summer, the bike ran good enough I put a over 1000 miles on it.
Recently I took it to a dyno to get it sorted beyond the "seat of my paints plug chops" and guess work. Now I have real data, which pretty much proves that all previous advice given to me on forums and chats at bike gatherings was wrong. The first run the bike was so lean my buddy (dyno owner) let off the throttle early and the dyno only showed the bike making 62hp.

I can't remember the a/f mix's exact ratio but it was way above the 13% you want to make maximum power. Based on my friend's dyno experience he suggested I go up to 130 mains and down to 15 pilots. Due to a mix up when I ordered my jets I ended up putting in 132.5 mains and swapped the pilots to 15. I did a plug chop in 4th gear doing about 80mph and the plugs still looked a little lean. I had ordered every size of jet up to 140 though because the 1st run on the dyno proved to me science will tell you the answer and friends are not science. I went back to the dyno with the 132.5 jets in and it produced 86hp. Yes, over 20 hp gained from changing from 120 to 132.5 jets. The a/f mix was still off so I put in 140 mains and moved the needle 1 notch lean. Then bike produced 89hp but the needle move was a bad decision so I moved it back to center notch and tried again.

With 15 pilots, 140 mains and needles in the center position the bike currently makes 92hp at the rear wheel with a 16% A/F mix. I ordered bigger jets and and plan to go back to the dyno again and get that mix to 13% at wide open throttle.

This is real data and I wanted to post it here so if anybody else builds a similar engine they can get their jetting real close before running it on a dyno 5 times.
I will post my final setting and final power when it's done. I also plan on making some timing adjustments to the electronic ignition once the carbs are dialed to see if I can squeak a few more hp's.

SeattleKz.....

Thats great info....Your bike looks very clean.
I just pick up a 79kz1000 with 1198cc kit , Web Cams Z4 , kerker, 29mm smooth bore Carbs....now i wonder what its making.

I'd put some real carb's on it. it ain't makin good power with those little carb's.

It's advice like that that led me to believe I needed to spend $7-900 on carbs when my bike wasn't running right. The real truth is, I just need to get the stock ones properly jetted. Thanks for proving my point.

If anything try it out with a set of 79-80 vm28s and see if theres a real difference, smoothbores and a 1015 sounds like a waste imho.

The kaw guy told me I was running out of gas at about 6g. with a 120 jet. and I needed a 132.
I went to 155 and it lit that bike up like crazy. I had to back the timing way down to get the powerband
dialed. I got rid of those dinky carbs and use the bs.s with 145 jet. Its too rich but I can start there.

I've been using these .407 mega cycle cams set a little late, from 8 to ten its strong enough to
stay with the 6oo's. But the carb I have is not competitive enough. I've just done a lot of bowl work to the heads.
I'm going to turn down the centers on both cams, . I'm thinking the power I'm looking for lies
in a good cylinder fill that requires over lapping the valve so that they normally would collide.
So I've radius both valves and I'm going for it. I've deepened the piston poclets to allow the needed clearance
and folks im tellin ya, somethings goijng to happen! I'm thinking rubber burning and melting into the horizon.
If the power band hits the wall too early I'll for godsakes turn around and set the cams back and finish
what I started. It's been fun like hunting in a way. one by one u stalk them and bang!. U eat one.
Then just drive and chew. Savor the flavor of vctory for a little while. the kaw was tougher than the cbr!,
the ymai was plain smoking. And well me where do u think your going! If u don't run of carb sizes,
who knows how much faster it will get. :lol:
find out what kind of torque can get the motor to lay down for free.

Why would it be a waste of time Floivanus? I am really close to having a perfect A/F mix with that stock carbs. Have you run the same bike with both 26mm carbs and 28mm carbs on a dyno and found a huge difference in power? My buddy put some CR29's on a bike and gained 5hp. The bike specs were 82hp at the crank and that was probably higher because motor companies always put down a number that's in a perfect world. I currently have 92hp at the rear wheel. I'd say that's a pretty decent number.

you are leaving power by using 26mm carbs but....... better to use a properly jetted set of 26mm carbs than improper jetted 28mm or 29mm smoothbores my hats off to you for taking the time to dial in carbs on dyno the difference in top end power may be 5-7 hp but through the middle is where the properly jetted larger carb makes due you have to remember Z1 900 had 28mm carb from factory and the Z1r had 28mm carbs from factory there is a reason for this and 29mm carbs would be an upgrade even on the Z1 and Z1r

The stock 1977 Kz1000 carbs were 26mm and worked fine.

I understand the CR's have better mid range adjustments and if I am unable to tune the bike to my liking with the 26mm's on the Dyno then I will consider getting them.

I think "but have no actual data to prove" the 28mm carbs would work better but still have mid range problems so if I do end up getting different carbs to solve mid range tuning I'll most likely get the CR29's.

SeattleKZ wrote: Why would it be a waste of time Floivanus? I am really close to having a perfect A/F mix with that stock carbs. Have you run the same bike with both 26mm carbs and 28mm carbs on a dyno and found a huge difference in power? My buddy put some CR29's on a bike and gained 5hp. The bike specs were 82hp at the crank and that was probably higher because motor companies always put down a number that's in a perfect world. I currently have 92hp at the rear wheel. I'd say that's a pretty decent number.

Dyno Jet dyno.... right?

SeattleKZ wrote: The stock 1977 Kz1000 carbs were 26mm and worked fine.

I understand the CR's have better mid range adjustments and if I am unable to tune the bike to my liking with the 26mm's on the Dyno then I will consider getting them.

I think "but have no actual data to prove" the 28mm carbs would work better but still have mid range problems so if I do end up getting different carbs to solve mid range tuning I'll most likely get the CR29's.

Two important things.....Ok...possibly3

1 - Jetting from 25 years ago doesn't apply to todays pump gas. Everthing wants more fuel than it used to require. That means bigger jets... You just proved that.

2 - Fuel level is very important to have properly set before any jetting is done.

3 - CRS29's will put a big smile on your face once they are dialed in. If you think it runs good now....wait till you ride it with a rack of properly jetted CRs..

LarryC wrote:

SeattleKZ wrote: Why would it be a waste of time Floivanus? I am really close to having a perfect A/F mix with that stock carbs. Have you run the same bike with both 26mm carbs and 28mm carbs on a dyno and found a huge difference in power? My buddy put some CR29's on a bike and gained 5hp. The bike specs were 82hp at the crank and that was probably higher because motor companies always put down a number that's in a perfect world. I currently have 92hp at the rear wheel. I'd say that's a pretty decent number.

Dyno Jet dyno.... right?

Sorry, what's the question?