KZ650 Carb Jet Markings

I've got a '78 KZ650 B2, had it for four years, stock air box and exhaust. Has been running just a tad lean on 1, 2, & 4 and recently a tad more lean on 3. Took the carbs off and found the problem with 3 (air box boot is shot, was leaking). My question for the carburetor gurus is this: Main jets are marked "06" and Pilot Jets are marked "50". Book says stock is 102.5 mains and 15 pilots. What sizes am I looking at on my carbs - what's a "06" and a "50?"

Bike runs well, 15.2 K miles. Got carb kits coming from Z-1 and will install stock mains and pilots in the absence of other wisdom and work it from there.

Thanks for the info in advance and ride safe.

Duncan R. McCoy
Boulder City, NV

duncan@bclibrary.org

It's getting bad when you've gotta reply to your own post. After giving this a lot of thought, writing the numbers down on a post-it, and turning the post-it around a bunch of times, it occurs to me that "06" on the main jet could just as easily be "90", a couple of sizes down from 102.5, and that would explain why the bike is running a bit lean. The "50" on the pilot jet seems to be a standard oversize from the stock 15 (ala Bikebandit parts list). Perhaps the last guy who got into the carbs jetted the mains too lean and compensated for 1/4-1/2 throttle leanness with richer pilots. Think I'll go with the stock 102.5 mains and the stock 15 pilots and see what happens.

Nothing like feeling like an idiot in front of all the KZ people in the country.

Ride safe.

Duncan R. McCoy
Boulder City, NV

'78 KZ-650 B2

duncan@bclibrary.org

don't be so hard on urzelve atealst ur working on it to find a solution !

You might wanna check your carbs where you found the little jet marked "50"
I think that you'll find the actual "15" pilot jet up above where that came from.

I was confused by this last week unti lI found a post that talkede about this smaller "50" jet.

You have a lates 70s lean set of 24s. The mains are #90s and the #50 jets are not shown on any of the fiche that I have but are plugged in ABOVE the pilot jets. When you unscrew the #50 jets, the #15 pilots are below in the pilot well. The purpose of the #50 jets is debateable since the carbs will run just as well without them as with them.

Thanks Wiredgeorge. The #15 pilots **were** under the #50. Took the #50's off (couldn't find them on the diagram either). Put in 102.5 main jets, float valves, O-rings, gaskets, new needles and bench synched. Bike is running fine, plugs look like they're supposed to. Better mid-range acceleration, very smooth. Must've had a high-altitude jetting setup. Did try it first with the #50 pilots on, bike was still lean, took 'em off, everything fine. Hardest part is stretching the air box boots over the carbs.

Duncan R. McCoy
Boulder City, NV

'78 KZ-650 B2 (15.2K Miles)

duncan@bclibrary.org

I see the set up all the time and doubt that Kaw had a "high altitude" set up but it is a good theory as you would have to be at about 11,000 feet to make those carbs work with #90 main jets. I test VM24s regularly using a stock airbox and #102.5 main jets... they work just fine and I can pull to redline cleanly. Not so with the #90 mains... those things are just too small. The #50 pre-pilot jets serve no real purpose as the opening on those jets is far larger than the #15 pilot openings so I can't guess why they used the #50 pre-pilots. I have tried the carbs without them and it seemed ot make no difference...

Wiredgeorge --

If the #50 pre-pilot has a larger opening that the #15 pilot, it shouldn't make any difference whether the 50's are in or out. My bike was running lean #50's in (clogged? Didn't look like it)and now that they're out, I have a very happy motorcycle.

My KZ-650 came to Las Vegas from Oklahoma (where it had sat in the guy's back yard for maybe 10 years). Vegas is about 2,200' and Norman, OK is about 600. Don't know where the bike was before Oklahoma, maybe Leadville, CO?

Anyway, happy bikes make happy riders.

Thanks for your help and ride safe.

Duncan R. McCoy
Boulder City, NV

'78 KZ-650 B2

duncan@bclibrary.org