KEIHIN CR-S 29 Jetting on 76 KZ900 with 4-1 and velocity stacks.

Aloha from sunny, warm and virtually COVID free Hawaii Island !

I had a friend who was trying to build a cool Z1 out of a 76 KZ900. Unfortunately, he is a proud member of the “more money than brains” club. He bought the bike from the mainland, not running and after bolting on all the beautiful new Z1 fuel tank and bodywork, the fresh 29mm CR Specials, velocity stacks (with appropriate cut outs for CR’s) and a 4-1 pipe (fake Yosh I think)......miraculously, it won’t run properly. Now it’s up to me to get him dialed in.

I get a whopping 75-85psi cranking pressure at WOT (warm engine) with leak down testing indicating bad rings and valves (after valve adj) in various cylinders.
Consequently, I’ll be sending off the head to be reworked (gladly accepting recommendations of mainland machine shops) and checking bores and replacing rings/pistons.

Also, the vacuum during carb sync was between 7-10 mm/hg......seriously low.

ANYHEW.......I’ve read here that CR’s come from the factory rich....
If you are running 29mm CR Specials on a 900 Kaw, please let me know what you settled on for your jetting.
This one came:
118 Main
62 Pilot
250 Air
Needle YY8

I appreciate your input.
Aloha,

7 to 10 inches of pressure is actually seriously high! Perhaps you meant centimeters.

hardrockminor, I very much appreciate you going out of your way to point out my obvious mistake in measurement units. However, the point of the post was for jetting specs of which apparently you have nothing to contribute. So I hope you feel satisfied in your indubious correction, it was noted.

If at all possible, it would please me greatly to hear from someone with some base jetting specs, per my request.

Aloha and mahalo.

There are several threads here with jetting information for the cr29. Here are two.

www.kzrider.com/forum/3-carburetor/60706...g-and-decel-backfire

www.kzrider.com/forum/3-carburetor/51452...-on-z1000mkii-engine

Many thanks, after searching almost an hour on the site, I never found those posts.
Thanks again !
Aloha !

I just use Google to search the site. You can search only a specific site.

site:kzrider.com cr29 tuning

No eBay APP ID and/or Cert ID defined in Kunena configurationHas anyone used this machine shop? Opinions?

Mahalo

Hi I've used CRs extensively
They are super easy to work with
And yes they always come rich
From the factory,I've only used 33s on my kz1000,gpz1100 and gpz 750
But 29s should be not far off

Your settings are all were you need to start
Start with clean plugs ,make sure your choke is fully closed on all 4 plungers
If you use the choke , get off of it as soon as it's running,
Air screw should be 1/2 turn from closed even though they recommend 1 1/4 out
Put a temperature gun to the header pipes to make sure they are all running the same
Within reason
Bleep the throttle to about 4000
And whatch the tach

Should go up fast and drop just as fast back to around 1100 or where you like your idle set

If it hangs up and comes back slow you must turn your air screw clockwise 1/8 increments to richen it up

If you bleep it and it goes up fast then drops below your set idle then slowly rises to the set 1100
It's too rich turn it out counter clockwise
1/8 increments until it sounds angry
There is no sense in looking at anything else until that can be achieved
I hope that a start

That tank looks familiar on the 750! Hmmmm.

You got me Dave!

No eBay APP ID and/or Cert ID defined in Kunena configuration

thekelzer wrote: Has anyone used this machine shop? Opinions?

Mahalo

He did my radical KZ750 twin head. custom valve train, porting, oversized titanium valves. reasonable prices and quick turnaround. also answered tons of my questions. his business name is Schumann Motorworks. he specializes in vintage Japanese stuff.

Does Schumann have a website?