'79 KZ650-C3 Jetting recommendations, please

Hi All; I know I'm gonna get flamed on this one because the question has been asked so many times. I have a daily driver 650-C3 with the pump type VM24SS (stock). I'm at 1200' altitude. I put a Mac 4 to 1 on and am using the DynaS ignition with stock air box and a K&N filter.
The problem: Idle seems inconsistent, sometimes it purrs and other times is popping and missing. The midrange seems pretty clean but the top is pretty flat and stumbles at mid/top transition.
The motor makes 165, 170, 170, 175 compression. The accel pump is functioning properly.
After reading 30 pages in this section, it seems the general recommendations are 102.5 mains, 5DL31-3 needles and new 15 pilot jets with air screws at 2 turns out. I welcome any and all feedback. Thanks and ride safe, Steve

Steve, 102.5 and 15's are the basic standard settings for most 650's, but your bike MAY have come with really lean 97.5's for emmision purposes! I'm at about 1100ft and have a Kerker 4/1, stock airbox with K&N, Dyna S. We are pretty much identical and I run 105's (no markings, not sure about pilot jets) My bike pulls hard at all rpm's. Every bike is different for sure, 105's may work for you or you may need 110's. According to WG we should be running at least 17.5 pilots. But with your setup 102.5's are lean as is with the 15's. Not sure about the needles. Also as far as your idle goes, how is valve adjustment, timing, carb sync?

P.S. Put your bike info and location in your signature line. Helps us help you better!

Post edited by: Bluemeanie, at: 2008/02/09 13:48

Post edited by: Bluemeanie, at: 2008/02/09 13:51

Steve,

(In my best Barney Fife impersonation -->) What you need to understand here is ... the KZ650, specifically the C-3 model, was impossible to jet correctly. Cosmic dissonance in diametric opposition to hedonistic calculus interests...it's just impossible. Fortunately for you, there is a solution ... give me your bike. :woohoo:

Just kidding!...listen to Bluemeanie, he's got you covered (and I had to take that shot before he did!)

-KR

post pics of your bike!!!...please!

Hi All. Thanks for the great info. The timing hasn't been checked. The sync is pretty good, well within the spec-manometer type gaging. Valve clearance is good also. I just realized that I had set the air screws at 1-3/4 turns out which would give a lean condition. That may be the idle problem. I've reset to 1-5/8 turns out and will see how she runs. I'll go with bluemeanie's suggestions of 110 mains and 17.5 pilots. Bad Kaw, you a bad man. . . Ride safe, Steve

shighley, just remember that air screws are opposite of pilot screws. Turning IN richens and visa versa. Try warming up the bike (short ride) adjust the air screw on ONE carb at a time to acheive the highest idle. Adjust idle down if needed between each adjustment, also give a couple rev's between each adjustment. Let us know...

P.S. DO NOT give BadKaw your bike!, he need's to buy his own damn 650!!

See that!? Try to do a 'good' thing and take a burden off a fellow biker, and whataya get?!!! I tell ya, us nice guys just get no where these days... ...buuuuuuuuut if you're still havin' troubles my offer still stands...yes, yes, I know...it's really very big of me, but hey...that's how I roll. :whistle:


:laugh: :laugh: :laugh:

Bluemeanie wrote: "According to WG we should be running at least 17.5 pilots. But with your setup 102.5's are lean as is with the 15's. Not sure about the needles."

Wow... I don't recall EVER saying that everyone should be using #17.5 pilot jets... I would use the set up the fella recommended for himself... #102.5 mains, #15 pilots and if his jet needles are 5DL31, then clip to 4th slot. The K&N drop in filter flows about the same as a stocker and unless the baffle is missing from a 4 into 1, most don't flow much better than the stock exhaust. It wouldn't do any harm to install #105 mains or even #110 mains since the oversized mains don't foul plugs but eventually, if you go too big, you will start to bog.

Try the jetting you suggested. The symptoms you described don't really sound jetting-related. Sounds more like a cleaning issue or air leak. To see if your main jets are big enough with your set up, try and pull redline. If you can hit redline in, say 2nd or 3rd gear, then your mains are fine. I suggested 2nd or 3rd so you won't get a ticket... If the bike can't pull redline, then bump the main jets a couple sizes... If your transition from mid-range to full throttle isn't smooth, I already suggested reclip to the #4th slot. The inconsistent idle is definitely a cleaning and/or air leaking issue; perhaps the choke plunger pads are not seating properly and allowing air to filter by which will cause the idle to pop up for no apparent reason while idling.