KZ700 Engine Rattle ?

Hi - I started my 84 KZ700 for the first time since winter. I’m getting a distinct engine rattle that wasn’t there last fall. It’s hard to tell where it’s coming from. Sounds worse at idle.

I took the valve cover off. Everything looks good, valves in adjustment, timing good.

The bike has a manual cam chain adjuster. Adjusting it while running does not affect the sound.

The only thing that’s I noticed is that the starter is acting funky. When I try to start it, sometimes the starter just clicks, sometimes it works. Would it be possible that the starter is hanging up somehow making the noise.?

I know this is not much to go on, but any ideas?

Thanks

My guess is two unrelated problems. The starter motor is a mighty reliable piece and is rarely at fault.
For intermittent starter function, I would suspect -
Weak battery
Starter switch - corroded contacts or broken solder joint
Wiring connected to the starter switch - loose or corroded connection, broken wire, missing wire insulation (The entire length of each wire, not just the end that plugs into the switch)
Main power cable to the starter loose or corroded connection

For the rattle, I would first suspect carbs need tuning -fuel level, synchronizing, fine tune the idle mixture

I would also check the exhaust system for rattles. you never know sometimes. With an exhaust vibration it would be more noticeable at idle, but the sound gets drowned out by the engine noise at higher rpms. You could tap the system at various points with a rubber mallet. Be sure to check the cross-over pipe & clamps, and make sure a heat shield isn't loose.

If you're certain it's an engine rattle, then I would do a vacuum synchronization, as noted by TexasKZ.
After that, I guess I'd check the cam chain & redo the tensioner as per the tensioner instructions.

MatiasMyles wrote: Hi - I started my 84 KZ700 for the first time since winter. I’m getting a distinct engine rattle that wasn’t there last fall. It’s hard to tell where it’s coming from. Sounds worse at idle.

I took the valve cover off. Everything looks good, valves in adjustment, timing good.

The bike has a manual cam chain adjuster. Adjusting it while running does not affect the sound.

The only thing that’s I noticed is that the starter is acting funky. When I try to start it, sometimes the starter just clicks, sometimes it works. Would it be possible that the starter is hanging up somehow making the noise.?

I know this is not much to go on, but any ideas?

Thanks

My guess is two unrelated problems. The starter motor is a mighty reliable piece and is rarely at fault.
For intermittent starter function, I would suspect -
Weak battery
Starter switch - corroded contacts or broken solder joint
Wiring connected to the starter switch - loose or corroded connection, broken wire, missing wire insulation (The entire length of each wire, not just the end that plugs into the switch)
Main power cable to the starter loose or corroded connection

For the rattle, I would first suspect carbs need tuning -fuel level, synchronizing solitaire.onl/ 9apps.ooo/
, fine tune the idle mixture

Rattle from bad sync carbs shall disapear when you go off idle? Keep stady 3 rpm and the sync shall not be a problem?

I have a 1983 KZ750 LTD w/ 4,000 miles. When I start the bike, (cold) there is a loud rattling noise that comes from the bottom end of the motor. After it is warmed up, the noise goes away. Any ideas as to a fix? Last year I dropped it off at the local MC repair place and they adjusted my valves, which didnt do anything.

There is no tensioner on that chain, so anytime the cylinder firing is not smooth and consistant that chain will bounce up and down. The reason I think it is probably the primary chain is because it goes away after it is warmed up (idle smoothes out), and the noise from a primary chain is usually described as coming from the left side.
If it was a loose alternator rotor, it would rattle all the time (after it got done chewing up the stator) and would have other symptoms. Loose cam chain noise usually sounds like it coming from the top, bearings knock, pistons knock when cold if clearance is excessive.
After considering the described symptoms, and eliminating all others, Primary chain is all that's left.

Of course it could be something really strange that I have not run across in the last 40 years, I do sometimes learn something new

Have you put fresh oil in it? If not I'd change it first. If the noise remains then adjust the cam chain tensioner.

I'd second this. It sounds to me like one of more of the carbs is flooding a bit on choke when cold, as it sounds like it's running on 3.5 cylinders. The carb sync could be out too. As soon as you bring the revs up above idle, the knock / clank stops.I think it's the clutch basket: on the KZ650 & 750, the clutches are notorious for having the shock-absorber springs on the basket get loose after a couple of decades, which makes a racket at idle unless the carbs are sync'd correctly. It can also make a screech / grinding noise if you do a fast getaway from a standing start, caused by the radial play in the basket because of the springs getting slack.Unfortunately there's no easy cure apart from stripping the clutch, installing stronger springs and re-riveting the whole thing back together. Every used clutch basket you can find is likely to be worn, and an NOS clutch basket is gonna be as rare as rocking-horse shit.

wrote:

I'd second this. It sounds to me like one of more of the carbs is flooding a bit on choke when cold, as it sounds like it's running on 3.5 cylinders. The carb sync could be out too. As soon as you bring the revs up above idle, the knock / clank stops.I think it's the clutch basket: on the KZ650 & 750, the clutches are notorious for having the shock-absorber springs on the basket get loose after a couple of decades, which makes a racket at idle unless the carbs are sync'd correctly. It can also make a screech / grinding noise if you do a fast getaway from a standing start, caused by the radial play in the basket because of the springs getting slack.Unfortunately there's no easy cure apart from stripping the clutch, installing stronger springs and re-riveting the whole thing back together. Every used clutch basket you can find is likely to be worn, and an NOS clutch basket is gonna be as rare as rocking-horse shit.

The 650 & 750 clutch basket doesn't use springs, they uses rubber bumpers.  I presume the 700 is the same.  There are replacement bumpers in the marketplace, and replacing them is an easy fix.

Thanks for the answer, I will check the exhaust system for rattles, though I did not hear the exhaust sound, maybe it was drowned by the engine noise as you mentioned. One again thank you for providing viable solutions, it was of great help. 

primary chain rattle common issue warm up engine good & give carbs a good sync, set idle 1400rpm