Stock spec's screwing with me...

Hey guys, my turn with a problem. I've had a Kerker on my bike for the last 28 years but lately I've been wanting to put a stock exhaust on the old gal. A couple weeks ago I picked up a free '78 KZ650 parts bike. The factory exhaust is in 7 out of 10 condition. Pretty excited to say the least. Installed exhaust last weekend and bike ran good but I know it should be running a little rich with Kerker jetting (105 mains, no number on all pilots, whatever rods cipped to 3rd slot,K&N in stock airbox) So, yesterday I pulled carbs and swapped in brand new 102.5 jets (not going back to the 90 something jets it came with), new 15 pilots and new rods (clipped to 4th slot) that came in kits that I installed a couple years ago. Now the bike starts fine, idles better than before, has better throttle response and pulls hard up to 9-10 grand. BUT, when you let the clutch out and go to take off it runs like it's starving for gas and feels like a cylinder or two is not working but once you hit about 4 grand the bike smooths out and flat takes off. Cruising on the freeway at 70 is fine with plenty of power and coming to a stop it idles perfect and has great throttle response. It ran OK before jet swap so I know all passages are clean. Jets, pilots and rods are all I changed. So what to you guys think as I'm getting tired (and good at it) of pulling these carbs.

B. sounds like you're very close. a smooth idle indicates pilots & screws close. I would try using choke at flat spot. if accelleration improves raise needles, if not drop. in "78, the b2 (early) c2,& d1 stock setting was 4th clip. late b2 &d1a used the 3rd. recent fiddling has shown me how critical needle/emulsion jets are for take-off. hope this helps.G

gane wrote:

B. sounds like you're very close. a smooth idle indicates pilots & screws close. I would try using choke at flat spot. if accelleration improves raise needles, if not drop. in "78, the b2 (early) c2,& d1 stock setting was 4th clip. late b2 &d1a used the 3rd. recent fiddling has shown me how critical needle/emulsion jets are for take-off. hope this helps.G

Good call, I didn't even think of trying choke. Don't know why but my old rods were clipped to 3rd slot (from top) So going to 4th slot it should have richened things up? FSM says 4th slot but then it also says 102.5 mains and we all know that I believe 70-80 650's ran with under 100 jets. Raising up again will put me in the last slot. Should I put old needles back in or do you think rebuild kit needles are OK? I rebuilt cabs about 20 years ago and don't remember if I used new or old needles.

Runs great now gane. Found out that the rods from the rebuild kit (Keyster I think) are much thicker than stock! Swapped out the rods and bike runs great! H2RICK brought that up over on KZ650.info . Thanks for your help though, bike now runs smooth and quiet with "new" stock exhaust.

Those pipes are beautiful!!

Looking good, John!

I noted that on a rebuild kit that the pilot sub-jets were smaller than stock. It pays to be careful and examine parts before replacement. Nice to hear you have it sorted.

650ed wrote:

Those pipes are beautiful!!

They are pretty decent, not as nice close up but being 31 years old they sre pretty nice, I'd say 7 out of 10. Not bad for a free bike! I would have driven up to LA just for the pipes.