Noise Identification

My 650 SR has a rattle at idle, usually I only notice it when I let it warm up on the kickstand for several minutes or when I've just pulled in from a ride, before I cut it off. The bike runs great considering it needs a carb cleaning - it starts easily, idles relatively well and pulls well, so I am doubtful that it's cam chain related, I would expect the irregular timing to be noticeable. The transmission shifts well and doesn't make any noticeable noise at speed (though it may just be masked by other noises?), so I am reluctant to believe the gearbox has significant issues.
The noise seems to stem from slight irregularities in the idle. It gets worse if, for example, I put the bike on the centerstand and engage 1st gear, since there's a lot of mass spinning and some slack in the drive chain. As it loads/unloads, the noise is quite apparent. Having the bike lean sideways on the kickstand also seems to bring it out a bit more than straight up/down, but that might just be me (maybe more to do with fuel sloshing in the bowls, causing idle variations?). Right now I'm suspecting the primary chain, and I've read that in some bikes this noise is pretty loud but not a problem. Any other opinions?

Ah, yes, the other thing I thought might cause it was the starter. Could its gear be sticking a bit and rubbing/almost catching occasionally, causing a sound like this? I'm leaning more towards the primary chain, but wondered if any of you had noise issues with the starter. I've also read about clutch noise issues, but this noise seems present in neutral and in gear (on centerstand), with clutch engaged or disengaged. The screwdriver stethoscope tells me it's coming from the lower rear of the engine case, between the crank and the gearbox somewhere.

Basically I want to know if it sounds like something that'll lock my rear wheel on me in a failure mode :blink:

Post edited by: cu zcar, at: 2005/11/11 09:08

I have a top end rattle in mine, I am sure it is a combination of timing chain and valve adj problems. I am going to pull the top end down this winter so it is going to get fixed

First, you won't notice "irregular timing" if your cam chain isn't tensioned or is stretched until it jumps a tooth on the sprocket and bends your valves. The noise you hear could well be a sign that the chain need attention. Another possible source of noises is your drive chain... Tension it properly as it may be sagging onto the chain guard or other piece of hard metal and rattling. If your starter is working as it should, it isn't likely that the starter clutch is hanging or sloppy where it is getting ticked but that is a possibility. Last, stuff in your transmission can rattle if the component is on the way out or is already broken but you would typically have problems shifting.

The noise is present at times when the drive chain is motionless, leading me to suspect the drive chain is not the (only) culprit. I do intend on checking my cam chain, though I should have mentioned that I do not hear any noises I would consider abnormal from the top of the engine (through-the-screwdriver method ). It sounds about like my Datsun's normal operation (also a chain-driven cam) when I listen to it through something.
I've yet to have a vehicle with a loose cam chain though, so I have yet to listen to a bad one...

Maybe I should have just asked what primary chain noise sounds like

Chain noise, regardless of where it comes from can make a lot of different types of noises depending on specifics as far as tensioning go... A loose drive chain can vibrate or bang, a cam chain tends to be audible only at idle and very low speeds... once the engine is up to speed, it may be making noise but wind may block it out or the frequency may get too high... the cam chain tends to be a rattling. Don't know about the primary chain question... sorry. Never heard a loose one.

First couple things to do with an OLD KZ are check the intake manifolds for leaks (they tend to dry and crack) and check the cam chain and valve lash... these things were often ignored. Once you make sure these things are OK, you can feel pretty confident you won't hurt the bike by riding it... and of course, make sure you change the engine oil as it is probably old... good luck!

I have always heard that it is not healthy to run your motor when your bike is on it's sidestand. Something about oil starvation on the right side. I don't know if it's really true or not, but I figure better safe that sorry.

It might just be your carburetors. When you say "they need cleaned", it may just be that and a sync problem. The 650 will rattle to beat heck from the primary chain if the carbs are not syncronized. This is where the 900/1000 is "better", if the carbs on them are all fouled up, the bike may run poor, idle poor, but no rattle because of the gear drive vs the hyvo chain on the 650. A rattling hyvo chain does not necessarilly mean it's bad, if the bike is not running correctly even a new chain will rattle because there is no tensioner on this chain. Of course as the miles rack up the chain gets progressively more stretched and the need for correct carb tuning gets more important to keep the rattle down. Other possibilitys could be a worn cam chain or those idler sprockets on the cam chain going bad and losing their centers. Just for info, I got 135,000 miles before the sprockets went bad, 150,000 out of the original canchain, 165,000 on the original hyvo primary drive chain and it was still rolling, but getting perty noisy . Finally retired that engine from service.

Mine sonded like a coffe can full of bolts until I synched the carbs. After that, it was rattling slightly from the cam chain. I modified the tensioner (see archives)and it stopped rattling altogether. I'm glad to here the mileage testimonials on chain wear. Thanks, Ron. Any special treatment to get that kind of life?

re: sidestand running, I have suspected this may be part of the issue and I've been warming it up mostly while sitting on it upright lately. I doubt that sitting at an angle will hurt the engine much so long as the oil pickup is immersed in oil, since most of the engine is force-fed oil by the pump. The cylinder walls may not receive equal "splash" lubrication I suppose, but my real worry would be the gearbox. I haven't studied the diagrams closely, but if it's like a car gearbox then it doesn't get "fed" with oil through passageways, it just sits immersed in oil and depends on this to evenly lube everything. Anyway, since I heard someone else say it, I'll probably be less likely to run the bike sideways.

I'll have to pop my cam covers then and check things out, and get things sync'd up if they're not. Oil, drive chain and sprockets were the first things I did upon purchase, so aside from keeping up with them periodically I should be in good shape for a while. With only 20k on the bike I'd certainly hope I'm not due for replacing the expensive innards, but then again maybe it was beaten and abused.

Thanks, all, for the replies! I'll have to check the archives for that tensioner mod. Is it a mod on the automatic-style tensioner I have, or the older style? I believe mine is meant to be service-free until the cam chain wears excessively, or something malfunctions at least that's what my manual tells me.

It's for the automatic one like yours. Our bikes are the same. I think there are threads on swapping for the manual style, too. The automatic one has almost 1/2 inch too little adjustment ability, compared to the manual ones. I didn't want to lose the riding time to get the manual one, so I made the automatic one longer. If you're not mechanically inclined...I'd go for a manual one from a different model like the other threads talk about. It's pull and replace. I've put nearly 6000 miles on mine since the mod..still quiet. I only added 3/8 inch...played it conservatively. My bike just turned 47,000 miles.

Post edited by: ronboskz650sr, at: 2005/11/11 18:33

OH! Lower rear of the case? My kickstarter did that until I took it off. It was loose on the shaft and would swing out and down just a hair causing the ticking from the almost engaging postition inside. At 20,000 miles it seems a little early for cam chain noise. Wire the kick starter up solid and see if it stops.

Well, lower rear of the engine (between crank and tranny) seems to be the focal point of the noise, IIRC ... been a few days now since investigating. If the kick starter actually causes the noise I'll have to fix it, I love using it instead of the starter. Call me old-fashioned, I guess.

I'll check everything out and report back if I find any problems. Thanks again everyone!