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Ok, I'll try to keep this brief. I have a 1980 KZ650-F1 with Kerker 4-1, K&N in stock airbox which I've owned since new. Last few years it's been hard to start and idled rough but on the road it ran awesome, ran right up to redline, cruised perfect. Sat for a couple of years and time to put back on the road. Went to Z1 and spent some $$$. Bought and installed new carb holders (hard as a rock and I'm sure they were leaking) carb kits, carb to airbox tubes (also hard as a rock)points and condenser, plugs. It starts much better, idles better and runs so much smoother. Now the problem, after starting it is very cold blooded (ok with that) but after a few miles (warmed up?) at about 50mph I feel like I have to keep giving it a little throttle so I reached down and gave it about 1/2 choke and bike suddenly perked up and took off. Plus about 80% of the time when I come to a stop and idle it appears to be running on 3 to 3 1/2 cyls. Take off and at about 3000 rpm it clears up quickly. Reused 105 mains (102.5 stock), added stock pilot jets, needles with clip (4th groove down) from kits. Checked floats and all were at 22-23mm from gasket, air screws are 2 turns out. Question...now it appears starved for fuel but before it seemed to run slightly rich (could take off ice cold with no hesitation)So where do I start looking??? Thanks guys

I would disassemble and clean the pilot and choke circuits and install #17.5 pilot jets when I reassembled. The pilot type is VM22/210 for your carburetors.

Thanks WG, I was kinda hoping you would pipe up! Come to think of it when I rebuilt the carbs I did install the new pilot jets (15's) from the kit. Makes me wonder if the ones I removed were 17.5's. I cannot see anything on them. Thats about the only real change that was made. Plus I used the new needle valves from the kits. All needles the same? The old ones were a little differant I think. I put the clip in the 4th groove on the new needles. Sound ok? Thanks again WG!!

A BUNCH of different jet needles were used on the various VM24 assemblies. In rebuild kits, I would be willing to bet that Keyster and K&L use 5DL31 clones as these are most common plus are common on some VM26s. These jet needles don't flow exactly the same as what may have been on the bike. You seldom need to reclip them lower than the 3rd slot. If you don't have the original needles, all bets are off and you will need to test different settings.

One last question and I'll leave you alone LOL I understand what your saying about the 3rd clip but would that not make me leaner?, which is basically the problem I have?

by lowering the clip you're raising the needle, which lets more gas in the engine.

Couple of thoughts here -- have you tried a bright light and magnifying glass attempting to read the old pilot jets and maybe one of them would have just enough of a number legible to determine whether they were 17.5 as recommended by WG. Maybe a good cleaning would allow continued use of the same stock pilot jets which performed well when new with the Kerker 4-1 and K&N air filter. Wondering also if you might consider returning to and using the same old stock jet needles (set in the 3rd clip as also recommended by WG). Could be wrong about jet needle wear, but believe jet needles can last a very long time before getting worn past their service limit. And have you checked the actual float levels via the clear plastic tube method (believed more accurate than the bench measuring method) to see if perhaps the fuel level is too low thereby causing a lean condition? Any leakage past the rubber vacuum tube caps? Any leakage in connection with installation of the new carb holders (might consider spraying them with starter fluid --with motor idling -- to see if motor picks up, which would indicate a leak). Didn't notice in the thread, but presume you have already double checked the ignition timing, compression and valve clearances. Certainly no expert here, just offering some food for thought.

I probably will reinstall the old pilot jets. That was about the only major change that I can think of. When I checked the float level they were all fine so no change was made there. Installing the new needles on the 4th clip would have richened it up some, so the old pilot jets may very well be 17.5's. Yes I have used a magnifing glass but after I pull the carbs I will check again. Thanks all...

Brought carbs to work (auto mech)and took apart. Found small piece of brass bent over (from slipping screwdriver) and partially blocking hole in pilot jet. Could explain idle issue. Am reinstalling old pilots and needles (ran great with them) Cleaned choke circuits and all others too. Proper bowl gaskets arrived last night (had to make holes in "wrong" gaskets)will reassemble and installe carbs this weekend. I really hope this cures my problem as removing/installing carbs is a real pain in the a**!! Will report back.. Thanks all..