KZ 650 Problem (stumbles off idle)

the bikes do that with the choke on, when I start mine I am moving the choke within a few sec and continue to do so until it starts to warm up

maybe i should have been more clear, I know they are supposed to go up a bit while on choke but not when i push it down. When I start it on choke the idle is around 1500 but as i push it down it will rev up to 6000.

yes it will, been there done that

alright, i guess thats just what they do.

I think I improved the stumble problem. I moved the needle clip down so now it is one up from the bottom and it runs better. It still seems to want to stall a little if I rev it quickley so the pilot screw might need a bit more tinkering. If I unscrew the pilot screw this will make the it richer is this correct?

before you keep playing with the carbs, have you checked the points, if you still have them, timing, and the advance, this also could cause the same problem

new points and condensers and the timing is dead on.

Have you checked for vacuum leaks? You should have the vacuum operated fuel valve. Check the line to it and make sure the rubber intakes don't leak or have bad vacuum port caps. If you have the VM24 carbs, I would go with 102.5 mains, 15 pilots, and put the needle in the middle (3rd) slot. Turn the air mixture screws 1.5 turns out from the seated position. From my understanding the air screws only change the amount of air mixing with the gas, it does not change the amount of gas going into the carb. Also, check for float heigth and no fuel flow restrictions. This is an outstanding combo on a stock airbox and exhaust set-up. Also, check the two diaphrams in the acclerator pump if aplicable. If you don't have an accelerator pump, the bike will have trouble with rapid throttle response.
Good luck and please keep us posted!

Thanks for the help Mellvis, I saw your located in Lebenon thats onlt 20 or 30 min from me, I live in loveland. Are you ever down at the Bike night at QSL in Milford?
I checked the carb boots and they dont seem to respond to spraying carb cleaner or wd-40 on them so i dont think they are leaking. They do have some small cracks but they dont seem to go all the way through. I still plan on replacing them soon though just to be sure. Is there any place else to check for a vacume leak?
I moved the needle to the 4 slot, one up from the bottom and it is better now. That made it more rich so im thinking of puting in the 102 mains that i have even though it came with 90 mains and then puting the needle in the middle slot.
Float height is good i checked that.
I dont have the air screws on it just the pilot screw on the bottom back part or the carbs and I have them at 1 1/8 turns out from a light seat.
It is running better now the way it is set up and the problem will get even better after riding for about 20 min.

Post edited by: onuLine57, at: 2007/06/27 23:21

Post edited by: onuLine57, at: 2007/07/06 16:47

Alright I hat the bike running good and I took it out yesterday for abour 45 min. On my way home At a stop sign i tried to accelerate and the bike would jerk forward on and off then it seemed losed power. i managed to get it home and pull the timing cover and the timing is a little off so i fixed that but it didnt help. i pulled the plugs and 1-4 seem to have carbon deposits on them and are a little wet but it isnt oil. 2-3 look ok. I tested the coils per the manual and they seem ok (3.8 ohms between the lugs and 12.8k between the plug wires). I didnt test them when they were still hot and I read in the archives that they can test ok when cold but then be bad as they get hot. Is this the problem or does it sound carb related?

I would get the hair dryer out and get the coils hot then test them. If 1 and 4 sparkplugs dont seem right I would suspect coil. Or the wiring goint to the coil.

I'm trying to figure out the Pilot mixture screw thing too. Are you guys saying that by turning out the Pilot screw you're adding more air and making it leaner?

Hi i have a 78 kz650sr it sounds like your valve shims are off, are you sure all 8 shims had the correct clarence.