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

One more update, pulled the plugs and checked them, 1 and 2 are fine, 3 and 4 are wet and a bit sooty. Cleaned up 3 and 4, and also tightened the spark plug wire on number 2 (turned out to be a bit loose). Still no improvement, though while turning it over by hand using the kickstarter, I did notice that it sounded like it was blowing a little air back out some of the cylinders. That seems very odd to me, but again, it could be a part of this bike. I can't imagine that it would run if the cam timing was off this bad though. Also, while running, when I would try to give it some gas, sometimes it would blow back out through the #4 cylinder (this was with the filters off).

The choke is working better as a throttle now though. But I still need a little (very little) choke to start it up and to keep it idling, even when the engine is warm to the touch. I am going to go look at the timing again, I am starting to wonder how much work the PO did on the engine.

If pods are all you have for intake and exhaust mods, I would think the 17's are ok for the pilot. The clip may go from the 3rd to 4th position, and the main jets would probably be one size larger than stock. Air screws are set initially at like 1-1/2 turns out.

Take a compression reading when the engine is warm and let us know the readings.

Little things could make a big difference when added together. Did you set the valves? Did you set the floats by the wet method? I sure would fix the coil voltage.

Just for info purpose only as your bike may be different depending on the year. My '78 650 has stock exhaust, stock airbox with a foam filter, 15 pilots, clip in the 4th groove down, and 102.5 mains. She's a hair rich. Valves and floats set right, and she's a little ripper. It's about as stock as a 650 can be.

Good luck, when you get her dialed in you are going to have so much fun.

And last update for the night. I checked the timing per the manual, and adjusted the points for the 1-4 side. Checked the spark at each cylinder and with slow turning it with the kickstarter it had a nice blue spark at each cylinder. Also rechecked the noise from the carbs, it is not blowing out (except the few times on cylinder 4, but is sucking in, sounds similar, but I put my hand near each intake to verify. I'll have to get a compression tester to check that so that will be a couple of days at least. But that is where she sits right now and still has the same odd engine behavior.

Ok, got it idling with no choke and even responding to the throttle. Not as snappy a response as I would like, but at this point even this much progress is making me :silly: . I ended up doing a bunch of things at once so I am not sure which one did it.
Changes I did:
1) The carb bodies are off a pumper, but the bowls are off of a non-pumper. When I first put it together I put in the airscrews for the pumper bodies, but while talking to a friend I started thinking about that and decided to go with the non-pumper style air screws (little longer) and set them at 1 1/2 turns out.

2)Never found an air leak, but I did tighten the vacuum port covers and put an extra cover from the carb holders onto the fuel tank vacuum.

3)Oiled the pod filters with some K&N spray oil.

I got a little improvement from these things, but still not enough

4)Didn't know if it needed it, but read about it in another thread about tightening the cam chain. So I did the book method with a slight mod from what I had read (think it was WG who said to do it somewhat like this). Rotated the engine 2 full revs using the 17mm nut on the crankshaft, stopped at the tdc, loosened the bolt and locknut, rotated it one more full turn and stopped at TDC, tightened it all back up and set the lock bolt.

5)Set the airscrews to 1 1/4" turn out.

Now it starts fine (still) and appears to hold a non-choke supported idle. Also I can use the throttle to rev it up and it responds. While it was idling I did more wd-40 vacuum leak testing and still didn't get anything but wd-40 all over my carb boots , but hey it runs so now I've got a tank to finish moding, some fiberglass to order for a seat pan, and either some turn signal stems or new turn signals to order for the front, and a whole lot more that I just don't want to think about right now. Thanks for the help and suggestions, if I hadn't been able to eliminate a lot of possible problems I don't think that I would have been able to get it working.
KC

Sounds like you're getting there. Did you do the coil mod and get 12v to them yet?

I've been working a similar issue with my 78' KZ650. Man do I feel like an idiot. I had the carbs rebuilt by WG. I did the coil mod. I fixed the charging system, replaced the battery, replaced the carb boots, new pods, lubed the throttle cable, and went up a jet size. Nothing changed. Finally last night I went to adjust the points for the first time since I've owned the bike. Noticed the PO had stripped the screws so the point weren't tight and there was virtually no gap. Went down to Lowes and picked up some new screws, adjusted the points and started up the bike. With that $2.50 fix and about 10 minutes, all the problems went away. Man I wished I checked that first. I know that you already mentioned your points and the same symptoms don’t always mean the same problem, but it probably wouldn't hurt to double check those gaps and contacts. Just my 2 cents.

No coil mod yet. Currently I am going back through the wiring, so hopefully this week I'll get that done too.

How's it going on your bike?

Slowly. I had to take a break from it as I found I was devoting way too much time to it, and not enough to family. Right now I have to make a rear mount for the new tank, make a seat pan, shorten a few more wires and put in a new horn wire.

For body work I need to cut my front fender, and then sandblast and paint fenders and tank and sand the side panels. Then bondo and I am going to try to paint them myself.

After that I need to get my seat cover done (not sure whether to make one out of saddle type leather or just go with the heavy vinyl).

And somewhere in all of this I need to rebuild the forks, swap out the steering bearings for tapered, and decide if I want to go for a running and ok looking (nothing really polished), or running and show quality running.

To date though, I have my wiring cleaned up and recovered, a new tank with mounts for the front, a new rear fender, got the front master cylinder hooked up and the brakes bled (need another speed bleeder for the other side), and I got the rear brakes flushed and working fine (the old fluid may have been original to the bike ). Also got a new set of front turn signal mounts to attach to the headlight shell so that I have a place to put my turn signals. Here is one of the more recent pictures.

I have cleaned up the garage since that was taken, but that is about where she is at right now. More work than I care to think about doing in the next 3 months. But it is progressing.

Oh, forgot to add that I need to get some new tires as well. The good news is that my wife is taking the money drain fairly well so at least I am able to keep getting what I need for each step.

When I get going again I will move this over to the projects section. thanks for the checkup

You were saying that plugs 1&4 looked fine and 2&3 were fouling, i had this problem with my kz650, it turnes out that at tdc my cam lobes were one tooth off of eachother, and it caused my bike to bog like yours, be sluggish, and pop when decellerating. I set them up equal, and the problems are now gone.