'81 KZ750 CV34 Carb tuning questions.

The baffles are in and I set the idle with colortune - I opened the throttle and it seemed to be in the ball park (not too lean, not too rich). I have the CV34's with pilot, mains and secondary mains. Didn't know there were any others out there. I don't think it's the jetting as it is also dependent on engine speed. I would assume that a jetting problem that was present at WOT and 6000rpm would still be present at WOT and 7000rpm.
I have another 8 sliders with intact diaphragms lying around. I'd like to be able to isolate the problem before I pull the carbs and start swapping parts.

The thing that has me stumped is that the problem only occurs at about 5500rpm and then disappears at 7000rpm. Under 5500rpm it pulls away smoothly and it just starts spluttering once I hit the higher revs. If the throttle has been 3/4 open from 3000rpm then the sliders must all be up before I hit 5500. So it can't really be a carb problem??
I did think it may be a voltage problem - too much voltage giving the coils grief. Not sure why it would sort itself out at 7000rpm though, surely it would only get worse. I did notice that the voltmeter starts jumping around, but I put that down to vibrations.

Did some more tests today and I think it's just a jetting problem. Will post the rest of the info on my project thread as it's pretty specific to my bike. Finished hijacking this thread now, thanks

Glad to hear you solved the problem.

calum wrote: Did some more tests today and I think it's just a jetting problem. Will post the rest of the info on my project thread as it's pretty specific to my bike. Finished hijacking this thread now, thanks

Just wanted to come back to this. I figured out that I was using resistor plugs (BR8ES) and had installed NGK resistor caps :pinch: Put in some B8ES plugs today and all is well. Still a very slight flat spot at 6500rpm, but it pulls out of it at about 6600-6700rpm - it's barely noticeable compared to before (no power from 5500-7000rpm).

For some odd reason I wasn't letting me reply to this post a while back.
I was going to say I think removing one of my baffles helped alleviate some of the flat spot that I get around that rpm range as well. Im starting to wonder if my issue is a jetting problem. I had thought the coil had fixed it but, it did it again the other day after the engine warmed up completely on a hat day. Possibly weak coil, and overly rich is my problem? When I get some change I'll get a one step down on the mains and do a plug chop to see whats up. Hope you're all well.

I'm assuming you have a Delkevic Megaphone and you removed the inner baffle? If that helped then you are probably too rich, although from the symptoms I'd guess too lean??? Just a guess though as I'm comparing it to my problem. I'm on the stock jets with my Delkevic but I still have an airbox. I was going to shim the needles yesterday to see if that helped the transition at around 6500rpm but I noticed one of the sliders was stuck. I freed it up and cleaned it and will see how it goes later today.
If the problem is worse at around 6000-6500rpm then you my want to shim the needles and see if it gets better or worse. From what I understand above that rev range the slider should be fully open, so if it's running well there then your secondary mains should be OK. If you shim the needle it will open a bit earlier and you'll be a bit richer for the transition (or rather, the needle will be further out at lower revs).
Someone please correct me if I'm spouting BS - this was the result of a long conversation with a neighbour.