1980 KZ650 Cold Star Problems?

[transam32]

Hello everyone, I'm new here and I did read through some posts already. I'm having a very strange problem with my 1980 KZ650 LTD and am hoping to find some direction here. My bike has been stored indoors for the past 11 years, and ridden regularly as recently as summer of 04. I have fired it up and ridden it for short periods many times with no apparent issues besides the common things like sticking floats or slight points corrosion issues that are to be expected. I'm having a problem this year that simply has me stumped, that is why I'm here asking.
I last rode this bike in the fall of 07....and it rode great, ran fine, with the exception of some fuel coming out of the overflows, it was a no harm ride. The carbs had been gone through the summer prior. ( 05 ) Since that ride it has not been on the road on a regular basis.
Here's the issue......I put some gas in it, primed it, and it was only running on 2 cylinders. It barely would idle full choke. I figured carb probem but I still checked the obvious.
- No fuel.....Yes each bowl was full.
-No Spark....I had spark on each plug.
-No Air.....Nothing blocked...it has 4 K&N Tapered filters on it.
I confirmed the dead cylinders VIA Pipe temp ( Hand Method )
@ this point I was a little confused. I figured I may need to pull the carbs just to check everything out to make sure it isn't a "crud floating around" type of problem. I grabbed my tools and headed back to the bike....tools & beer in hand I tried it once more and it sounded different. I could keep it running and I'll be damned if it didn't fire right up and ran quite normal????
The only change I made was to walk away and get my tools. ( 2 mins, max) and this thing went from dead as a door nail to running like usuall.
This afternoon I came home and tried to fire it up, ......it did the same thing....running on 2 cylinders ( same cold pipes) . I thought ...maybe stuck valves when cold...so I promptly did a compression check......120-130 for all cylinders. Fired it back up with the same dead cylinders and thought maybe bad coil??? #1 and # 3 cylinders are the cold ones , # 1 & # 3 DON'T SHARE THE SAME COIL??? I got the problem to repeat I could keep it running @ Idle if I manually pumped the accelerator pump lever on the inboard left carb. Once the motor temp was warm enough that I could'nt touch the pipes that where firing anymore....I let it sit for a few minutes , then it fired up on all four cylinders and ran fine. WTF is wrong with this thing, and what am I missing?

[transam32]

Sorry.....Here's the quick info.
1980 KZ650 LTD, 4-1 header, Mikuni Carbs(<-stock Not chrome capped) K&N filters. Stock ignition ( points )

[A2rider]

You might want to join this forum if you get no answer here.

kz650 - Index

[Iceman Too]

New plugs all around?? Wires in good condition??? Sounds like one of those easy to check. Good luck.

[herk]

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[transam32]

Yep, new plugs, checked the wires ( mine don't unscrew on the coil side ) re connected the supression caps. It really acts like a stuck exhaust valve until the motor warms up a bit, then it runs like a champ.

[antiq]

Any possibility of grime on the plugs? They can spark down the outside if dirty. When did you last change your oil? If it's sticking valves maybe an oil change would help.

[transam32]

I have checked them, they still look like new, the good cylinders are a tad carboned up from me keeping it going with the accelerator pump, but when I swaped them into the dead cylinders everything stayed the same. I just changed the oil before I fired it up for the season. I'm wondering if maybe I could have a timing or points issue. Has anyone ever had something like this happen to their bike? Maybe a strange Kawa thing. I'm going to clean up the coil mounts cause the look a litttle rusty, maybe losing contact. I fired it up last night after I posted here and I'll be damned if it was firing on #1&#4 cylinders instead of the usuall #2&#4. ???? This is making me crazy. I'm also going to pull it away from the wall so I can get to the points. Maybe there's a seal leaking a tad of oil in there causing a misfire??? Also , the compression check pretty much confirmed it for me that the valvetrain is functioning properly. Where is that Stargate guy?....after reading through more and more posts here, he really knows his stuff!!

[A2rider]

Stargate definitely knows his stuff. So does elr658 and GREENISBEST, who are mechanics. Maybe they will show up and help.

[PNKFLYD]

I'm having the same problem. Only mine was not firing on #1 and #4 after I changed the plugs it fires on only 3 #1 still not firing. The pipe no matter how long it runs never gets too hot to touch. I'm thinking that maybe the jet is clogged so I am going to tear down the carb again and check it out. I also own a 1980 KZ650LTD.

[transam32]

Pnkflyd, That is what mine seems to be doing but the plug swap does'nt change it and once it warms up it runs completely normal. After staying away from the bike for a bit ( plus the battery is finally dying ) i'm kinda leaning towards the points but I'm still hoping for an expert to chime in here and give me a strong direction to lean towards. It's colder here today so...I'm not to keen on getting it out of storage and in the way quite yet anyhow.

[antiq]

I've had a few spark plugs over the years that were just plain bad out of the box. Try using the best two of your old plugs in the non firing cylinders. If it works you'll know where the problem is.

[StarGate]

Well I no expert or professional but the first things I would do after what you have done already, would be check for tight valves and partially plugged jets/passages. As elr so often says, "valves to the loose side of tollerence".

[transam32]

Antiq, I've swapped the plugs all around and it doesn't change at all.
Stargate, yeah I'm gonna check the points area for contamination and binding then the carbs are coming off if I find nothing there. Thanks to everyone.....I'll keep yah posted. What a PITA these things an be sometimes.

[transam32]

ok, little update with some more info and questions. I fired the bike back up and same problem, this time I tried to let it warm up enough to repeat the symptoms so I could do more diagnosing. I grabbed the choke lever and cycled it quickly from full choke to full off MANY times. I noticed a difference in the engine speed and sound. I probably cycled it 50 times total. The thing came to life and now runs just fine. (about 2 minutes ago ) So I'm gonna pull the carbs for sure. Here's the question before I tear them apart. Is there a way I can remove the little choke plungers and inspect them without having to pull the carbs off the rail? I really don't want to have to re-synch and all that crap. I don't have them off yet but I'm sure I will sometime this weekend if not tonite. The carbs are the Mikuni's with the that DON'T have the Chrome round tops.

[transam32]

Now, just 5 minutes after the last post I tried to fire it up and back to running on 2 cylinders.....immediatly I went for the choke lever. I restarted it and kept it idling then cycled the choke a few times. While I did that the motor would would get on all 4 , then back to 2.....multiple times. What the hell does that choke effect within the carbs that could do that??? ? I had it going from 2 -4 cylinders just by toying around with the lever. I'm getting a little frustrated, but at least now I know how to make it run great, then run like ****. any advise would be greatly appeciated. I really don't want to have to do a complete re-build for one stupid o-ring or something like that in the choke circuit.

[StarGate]

Jets are plugged and the choke is just giving it fuel it can't get through clogged jets. Clean your carbs!

[MSGAmling]

TransAm32, sorry to hear you are having the same issue I am. At least I know I'm not alone in trying to track down this gremlin. My issue is with the #1 cylinder cutting out intermittently, and at times on a ride over the past week or two, a second cylinder cutting out (I can't track which one because it will come back again after a short cut out) intermittently as well. While riding, I start on all 4 but get one or two cutting out intermittently when getting on it a bit (but only occasionally cutting out) and then getting full power after rolling on the throttle on a straight. So far I have tried:

Replaced all 4 carbs with a freshly rebuilt rack of Mikunis (same as yours) and a new in line fuel filter. Synchronized the new carbs and put in a new air filter as well.

Ran a tank with Sea foam through the new carbs after the problem resurfaced.

Cleaned every electrical connection and applied dielectric grease and put in a fresh set of plugs.

Checked all valve clearances and they were within tolerance. Did a compression test and got about 150 psi on all cylinders.

I tested both coils and found one only slightly out of spec on resistance.

Even when I can replicate the problem with the bike standing still, and the number 1 pipe is running cold and I throw a timing light with an inductive pick up on the wires, they all show that they are firing.

Today, another set of coils and wires I ordered came in and I just picked up a 30 amp 4 pin relay and wiring. So, this weekend I was going to do Wired George's Coil mod to make sure I was always getting the full primary voltage to the new coils and wires when I put them on. Hope this cures it.

If you or PNKFLYD find what is causing your problems, please post the solution. I am getting at my wits end on this and running out of things to try. The old sage at the parts store had a few thoughts that I may check out as well. He advised looking for air leaks or additional blockage on the number 1 carb again. His rationale was that since a bike spends more time on a side stand that gravity causes the number 1 carb to run into more fuel problems and is more susceptible to bad floats (not the needle and seat, but the floats themselves).

[transam32]

I'm gonna pull em' You think it's just the mains got some crap in em'....I feel its sure a carb issue now, but its so strange that it''s this intermitent. If I really think about it though.......if it's something that was above the taper on the jet then eventually the suction would at least pull it out and it'd float around till it's shut down for a while then sink right back down the tube back into the jet. Yeah...I'm at very least gonna pull and clean the mains and seat/needle. If it's something that simple I need to kick myself in the *** and give a sucker to everyone that has contributed to this post. I really do appreciate all the help.

[transam32]

MSGA.....I must have been posting while you where....
That sounds like the same thing to. I'm trying desperatly to solve this and I certainly hope I don't have to drop that much into it to get it going. Right now I'm shooting for cheap if not free fix. Your post really got me down a bit, cause I don't want to have to go there. It's all good....I'll see what I find in the carbs before I get to much more insane. ( or drink to much, that will explain some of my bad typos. ) With your situation after re-reading it.....that sounds mechanical to me. If you have a dead cylinder and the timing light picks up the signal then it has to be no fuel or no compression.......You might want to look into maybe a bad valve or galled guide issue.