KZ 650 Runs, but bogs when I open the throttle. Any ideas?

Before I bought it my bike had been sitting for a couple of years as the po had some issues with the carbs. I rebuilt the carbs and rejetted them to 107.5 mains and 17.5 primaries with the stock needle clipped in the 3rd groove. When I went to start it for the first time, I kicked it over about 10-20 times to get the oil into the system without having any gas in the carbs. Then I turned on the gas and it started on the second kick with about 3/4 choke. :woohoo:

The only downfall is that after starting and idling for a few minuts (the idling RPMS were starting to pick up) I started to reduce the choke and to try and open the throttle a little. However when I did this the bike would bog or cut out completely. And if I cut the choke out completely the bike would die.

Is this something in the carbs or just something with still being cold? Also, there are 3 vent hoses on the sides of the carb, one near the back of the second carb and 2 near the front (one on the second and one on the fourth carb). As I understand it the hose that connects nearest to the engine is the vacuum for the fuel petcock, are the other two just vents to hang free with the ones off of the float bowls?
Thanks,
KC

Question please -- exactly what carbs are these?

These at the stock mikuni vm24 with a disabled accelerator pump. I swapped the bowls for some non-pump bowls and then put them all back together after an indepth cleaning.

Ok, plugged to two front vent lines, no effect.
opened the two front vent lines as stated in another thread, no effect.
Checked my points gap, just under 0.014" (within spec), and cleaned my points, no effect.

However, I did find that when the bike is warm and I start it with 3/4 - full choke that it will rev right up without a worry.

One side thought, I put the air screw (the one that comes in from about a 45 degree angle from the top at about 1.5 turns out. Do I need to turn it out some more or does this sound more like something other than the carbs.

Also, found that the spark advance isn't frozen, was able to move it somewhat by hand.

So, with the choke on and the slides closed it will rev all the way up without any troubles. Also checked the power to the coils and measured it at 9.96V per coil. Looking at doing the wiredgeorge relay for power to the coils.

I can't figure it out as the bike will start on the first kick even when cold. It is easier to start this bike than it is to start my dirtbike. I am going to order some new points from z1 and possibly some new pilot jets. Right now I have 17.5's in there, should I go to 20's or 22.5? I am also go to oil the pods that are on there and see what effect that has on it. I just need to get this sorted out soon as I would like to finish my tank, seat, fender, etc in the next 2 months so that I can ride it to work.

Thanks in advance for any advice or help.
KC

It shouldn't be able to do a warm start with full choke. Seems like it's too lean at idle. Going larger on the pilot jets may work, but I'd check some other things first. Have you checked the float levels? Do you have good compression? Are your intake boots in good condition, or are they cracked and allowing air to leak past? What do the plugs look like?

You don't have three vents. You have two vents and a vacuum port on #2 carb I think. The fitting in the rear is the vacuum port. Go to our website and have a look at VM Carb Connections link under wg's Tech Stuff Index for pics. Don't plug the vents. Plug the vacuum fitting if not used for connection to the petcock.

You can see the carb connections on WG's carb site here, second pic down: WG carbs .

There are two vent hose connections, one on carb 2 and one on carb 4. The hoses do just go up and come down next to the airbox, and just hang.
The other connection on carb 2 is the Vacuum connection, that connects to the fuel valve on the tank. Your fuel valve will have ON, PRIme and RES on it if it's a vacuum petcock. If the petcock only has ON RES and OFF, and only one nipple, it's not a vacuum petcock, and the second connection on carb two will need to be capped.
The four carb manifolds (between the carbs and engine) will have 4 caps on the nipples, which are used for synchronizing. If any of these 4 caps are missing, find some.

WG is the carb guru. See if you can get his attention on this thread.

There he is.

Ok, going to pick up some vacuum plugs tonight after work and try it again, I though that I had it plugged well enough but I want to be sure. I have vacuum operated tank spigot, but I would also like to get away from that if I could, unless there is a large advantage to having it setup like that. If that doesn't work then I am going to float height, jets, and points in that order.

As for the carb holders, they are free of any cracks and still somewhat pliable (took a lot of pushing to get the carbs in) and I installed new caps over the vacuum ports on them. Is there anyway to test for leaks around the carb boots where they connect with the carbs? On the engine side I put a thin layer of high-temp engine seal (the grey stuff for honda dirtbike valve covers) to help seal the carb holders to the engine. I used it as the rubber on the flange looked a little worn.

I think I will hold off on my z1 order for another day until I can get this narrowed down some more. Thanks for the ideas, I'll let you know what shakes out.

Spray some WD40 around the manifolds fore and aft of the carbs when the bike is idling.
If the revs change/climb, you have a leak somewhere.

Before doing anything else I´d move the needle clips to the 4th groove (second from bottom). And Rstnick gave some good advice too.

Ok, I tried a new vacuum plug, I tried wd-40, I tried backing the air screws out another 1/2 turn and still got nothing. Though I did listen and while trying to open the throttle I end up with a shush-shush sound than that of a 4 cylinder bike trying to rev. Kinda like the sound of an iron lung at about 3 cycles/sec as my bike attempts to live.

My next one is to check the carbs, replace the points and bump up the pilot jet a size or 2. I would adjust the needle, but that shouldn't be causing a problem just off idle if I understand the needles purpose correctly. If I turn off the choke I cannot get it to idle. As soon as I start adjusting the idle set screw it will die. However I can use the choke as a throttle (not as responsive as I would like, but hey throttle control is throttle control .

Do my next steps sound reasonable? This is the first 4 cylinder bike I have worked on, I rebuilt a v twin with dual carbs and it ran like a champ, this one is starting to make me wonder. Thanks for all of the suggestions so far, anything I can do to start eliminating potential problems.

Just to clarify, before putting them all back together I made sure that everything worked and that all passages were clear.

One side question though, is there a vent tube that connects the #2 and #3 carbs like the ones that go from #1 to #2 and #3 to #4? The PO had one on there so I wanted to make sure. Bear in mind that these are the pumper style carb bodies.

Thanks,
KC