Choke Related Idle Problems

First a little history. My 77KZ650C1 sat in my basement for about 10 yrs until I recently started restoring it. I removed & disassembled the carbs & soaked them in Berryman's. I tried the spray carb cleaner route first to keep from having to remove them from the rack, but two slides were stuck & wouldn't unstick. The Berryman's did the job. Then, I did the manual bench snyc using 1/8" ball bearings. Things looked good. I finally got it all back together and tried to fire it up(with fresh gas). It cranked and ran a little rough (but not too bad) on choke. I let it run for about a minute, then I backed off a little on the choke. It then rev'ed up to about 4000. I backed off on the idle adjuster a little-nothing. A little more-nothing. After about the 4th tweak, the idle dropped a lot and almost stalled. I tweaked the idle up a little-again nothing. After about the 3rd increase adjustment, the idle went up to about 3000. I kept trying, but I couldn't get a stable idle. When I rev'ed it a little, it was very slow to return to idle. The valve clearances were supposed to have been adjusted about 300 miles prior to parking it, but I plan to check them anyway, but I haven't yet. Based on some searching of the archives, I suspect air leaks on the carb intake boots. Is this the likely cause? Could it be a problem in the chokes? Also, I've read of using WD40 sprayed on the boots to diagnose leaks. How does this work? Do you spray one boot at a time, or try to get them all sprayed as quickly as you can? Is the idle supposed to smooth out or go higher?

Thanks.

That's how mine are too. I think this is normal for these bikes, from what every one has posted.

I find if it goes to 4000 it will come back down in 5-10 seconds. But I don't like a cold engine going that high so I move my choke down until it passes that range. I try to find the spot it will idle at 1500-2000. I usually have to keep a finger on it and slightly move it up and down to stay there, else it will drop to under 1000 or rev up to 2500-3000. It sure is finicky.

My bike idles REAL high with full choke too.Lke OKC mentioned start it and slowly lower choke till desired RPM let motor warm up a bit.

As for not idling check for vacuum leaks.I use a little shot of carb cleaner which I have found work better than wd40.

Thanks for the tips. Last night I ran it some more. When I first cranked it (on full choke) it rev'ed to about 4000. I backed off on the idle to fix it. After it warmed up the idle was too low. I guess I'll have to modulate idle at cold with the choke lever.

Also, I noticed last night after it warmed up that there was a kind of a spitting noise coming from the carbs every 3-4 seconds. I have pods and put my hand under them and noticed that the spitting was coming from different carbs, not the same one every time. The engine also tries to bog if I open the throttle too fast. I know that slide carbs can cause this, but they seem to bog a little too easily. So I think it may be running too lean. The only thing I haven't set back to stock on the carbs is the air screws. I set back them to where they were before disassembly, which was 2 turns out. My Clymer manual says to start at 1 1/8 turns out. Which setting is leaner?

Thanks.

Post edited by: bemoore, at: 2006/05/18 07:58

More out, more lean. Have you tuned this bike yet? Adjusted valve clearances? Have you checked compression? Have you measured voltage going to the coils? Have you replaced the intake manifolds and checked the rubber vacuum caps on the intake manifolds?

These bikes have a choke system which is at best, primitive. It provides a richer mixture by richening the circuit while the choke is engaged. The choke plungers are not designed to precisely meter air and fuel so you will likely rev a bit high. I suggest you set the idle speed when the bike is warm then leave it alone. Use less choke to achieve an acceptable warm up idle speed.

No, I haven't tuned it yet. The carbs were gummed up with two slides stuck. I hoped to clean the carbs & sync them (mechanically) & get it running well enough to ride some. And, as I get time, do all the other tuning. I have re-torqued the head bolts and checked compression. The inner two cylinders (2&3) are ~158, and the outer two (1,4) are ~151. Measurements taken while carbs off the bike. I haven't checked the coil voltages, valve clearances, or timing, but I plan to eventually. The intake boots & vacuum caps were check while the carbs were being cleaned & they looked good and felt pretty soft. Unlike the airbox-to-carb hoses which were hard as rocks. I'm currently using pods, but I will switch back to the airbox when I'm comfortable I've got the carb problems resolved.

Thanks for the info, George.

what kind of pods are you using? i seem to remember there being a thread about people haveing issues with a cheap brand of pods as opposed to the k&n pods. Something to do with the rubber blocking vital circuits at the intake end of the carbs? maybe someone can refresh my mind lol:P

My pods are not K&N. They're one of the cheaper ones, but I can't remember which. I'll have to take a look tonight when I get home.

kx_125_pilot wrote:

what kind of pods are you using? i seem to remember there being a thread about people haveing issues with a cheap brand of pods as opposed to the k&n pods. Something to do with the rubber blocking vital circuits at the intake end of the carbs? maybe someone can refresh my mind lol:P

That problem was on the cv series carbs not the vm carbs.