76 KZ900 Continued Engine Problems - The Saga Continues

I am just about to my wits end trying to figure out why my KZ900 doesn't perform right.

Disclaimer: I am no expert and am learning about these things daily, so if I appear ignorant, its largely because it is true. Any help or advice you can give would greatly be appreciated!

Symptom: The bike idles fine, does not miss a beat in neutral when you rev it, etc. Sounds great other than some backfire. However, when riding the bike and accelerating at a normal rate, in any gear, the bike gets to around 4-5k RPM and starts to lose power. When you get to this area of the throttle you can go wide open and it will quickly resolve the issue. However, if you hold the throttle at this RPM range, it will make a noise I am going to **try to describe. It almost sounds like some one smacking an empty beer can with a rock (from the top of the motor) (now that had to be the first time anyone used that analogy) - And at times, sounds like a 'sucking' sound is coming from the top of the motor, maybe even the carbs? The smacking sound happens just a few times when this happens, not dozens, but maybe 4-5 times. So maybe the beer can analogy might even sound like a clicking or slapping sound? This noise is never heard at any other time. Slightly lifting the choke does not help, however, putting the choke wide open does help a little, but I imagine that is no different than going wide open for a brief period. There are times that after riding the bike for extended periods of time (getting it really hot) that the bikes symptoms completely dissapear. I hope I described that the best I could. One other thing to note. The bike is really powerful and runs great when you are 0-70 in a hurry, its the normal cruising and winding the gears out to around 6-7k rpm that its most noticeable. I also get a lot of backfire (poping) when I decelerate.

Repair History to solve this issue:

1. New intake boots. Checked for leaks. OK
2. Rebuilt carbs by wiredgeorge. (This issue was there before I got the carbs, and it got worse when the carbs were installed)
3. Valves adjusted 1.5 years ago and the guy who did it mentioned that one of the valves was completely closed and he adjusted them for me. (suspect area)
4. New dyna coils and Dyna S ignition. I put these on this week and it has actually gotten worse since.

More on #4. I timed the bike with an ind. light. - I clamped Wire 4 (last wire on right side of bike) and lined up the 'T' with the mark at idle. I then clamped wire 3 (second to last on right side of bike) with the 'T' mark at idle - I then confirmed that the bike advances to 'F' at 3k rpm. It actually performs the worst when I am at these settings. If I advance the entire place counter clockwise a 1/4 inch, it gets a little better. Now explain that !

I am starting to think the something is up with the valves and I need to dig in there and make sure everything is set properly and I have no big issues going on. I am going to have someone help me do that with the assistance of wiredgeorges excellent article on his web site.

** Other than this, what else could I be looking at here?

Your time to respond is sooo appreciated... I love my KZ, but I would love it more once I get this resolved.

Post edited by: thetemples, at: 2007/05/24 10:38

Chris,I think it's time to do a compression test,Bud.
That will really help Us out.
Have You looked into the timing chain adjuster?

I'm no expert either Chris, but the fact you've got weird noises points at the valve adjustment/cam chain.It's safe to say if WiredGeorge did your carbs then they're o.k.I wonder if the chain jumped a tooth/sprocket worn?, this may explain your strange timing advance as it could[this is where I get shot down:) ] give generally at certain rpm's , a better alignment of adjustments?
Interesting problem, don't lose heart, you're in the right place. Sorry can't be any help.Best of luck.

thetemples wrote:

...timed the bike with an ind. light...lined up the 'T' with the mark at idle. I then clamped wire 3 (second to last on right side of bike) with the 'T' mark at idle - I then confirmed that the bike advances to 'F' at 3k rpm. It actually performs the worst when I am at these settings. If I advance the entire place counter clockwise a 1/4 inch, it gets a little better. Now explain that !

Forget the T mark when setting ignition timing. The T mark is to determine TDC (top dead center) position of piston when adjusting tension on cam chain. The ignition is supposed to fire before TDC. That's why the T mark comes after the F (firing) marks on the timing advancer unit. So use the F mark when setting ignition timing-- not the T mark.

Addendum: Left Dyna module triggers left coil to fire cylinders 1/4. Right Dyna module triggers right coil to fire cylinders 2/3.

Post edited by: Patton, at: 2007/05/24 13:10

Post edited by: Patton, at: 2007/05/24 13:11

Damn Damn Damn ! You are so correct.. I've been trying to time this son of a gun with the "T" mark all this time... I wonder now if I was also doing that with the points ignition.. probably.. I'm such a noob. That make sense why advancing the plate helped a bit.. I cant wait to get home from work to try the F mark... I will keep you posted and regardless.. I am going to go through and check the compression, valve adjustment and timing chain.

thetemples wrote:

...going to go through and check the compression, valve adjustment and timing chain.

Permission granted to use the T mark when adjusting tension on timing chain. :laugh:

Best to set automatic timing chain adjuster with engine warm. Use kickstarter to turn engine over a few times. Remove points cover and use 17mm "nut" under points cover to turn crank forward until either T mark lines up with mark on engine case. Never go backward. If T mark goes slightly too far, just keep turning forward until T mark lines up perfectly without going past engine mark. Cam chain on rear side is now in its slackest condition. Next, loosen lock nut and bolt on adjuster under carbs. (Allows spring loaded plunger inside to move). Tighten bolt (snug is tight enought). Then tighten locknut (Not Godzilla tight). Replace points cover. You're done!

Update:

I spent some time tonight working on the KZ and I was able to set the timing properly to the "F" marks. I gave it a stroll around the block and no good. Runs a little better, but same problem exists.

So then I proceeded to remove the valve cover and first check the cam chain tension (which I do not suspect is a problem, I have no noise at idle) - I believe the tension is fine and I assume I have an automatic tensioner?







I didnt touch any of that. I then proceeded to check the clearance of my valves.. I checked the gap when the lobe of the cam was pointing up with no tension on the valve, like this:



Correct?

All but two valves were within .005-.010mm (not sure if I have my .0 or.00 correct, but I double checked it when I had the procedures and clearances from wiredgeorges site, most being around 6-8 (thats .006mm) I believe.

However, I had one that was .013 and another that my smallest .004mm would not fit in, however, the ring around the bucket spun when the lobe was pressing down on it.

From what I've read.. I need to get these two into adjustment by buying a couple of tools and a shim kit.

Would these clearances account for the symptoms I am experiencing?

I also again verified that I have no air leaks on the intake side. I swear this all sounds like carb problems to me... help!

if the cam chain has a bit of streach sp, in it you may need to adv the timing just a bit, also since the carbs were done, by the expert, you will still need to sync them in on your bike to make it just right, also what is the condition of the fuel filter?

Filter and gas line is all brand new. Carbs have not been synced to this bike yet. I agree on the advancing of the timing, but is it just trial and error at this point?

A couple things.

Make sure you are clear on your valve clearences. Try to stick with either metric or english measurements. From the Clymer manual, valve clearance is 0.05-0.010mm or in english 0.002-0.004 inches.

You describe one valve where the "ring around the bucket spun when the lobe was pressing down on it." It's been a while since I did valve clearances, but as I remember, the valve shim buckets don't spin eaisly when the cam lobe is pressing down on them. It sounds to me like you might have something broken under there.

By the way, what's all the red gunk in there? If you have a bunch of that floating around, it could possibly be causing sticking valves.

Good luck.

Sorry, I meant to say that the valve with no clearance (or at least that I can't measure) spins when the lobe is NOT pressing on it. It was something in wiredgeorge's article that he pointed out that if you cant measure for clearance but you can spin that, you do have 'some' clearance.

the gunk is some retards attempt to put orange gasket sealant on the bike instead of a gasket and got it everywhere. I am removing that now. I have the gasket. Its a mess, but it doesnt seem to affect the moving of anything and I dont see any pieces floating around in the oil or anything.

The .13 clearance isnt so bad, but while your in there you might as well fix it. The one that you can not fit your smallest feeler under is probably a problem, I'd make sure to fix that one. Could be hanging a valve open if there is little to no clearance.
The way you described the noise you hear I thought you must be talking about pre-ignition, but if the timing is set right then I have no idea what it could be.
What do the spark plugs look like? You should be able to tell if your timing is off, too rich, or too lean from the plugs.
All I got for ideas