Hey all -

I have an interesting noise I need a bit of help with.

I have an 07 klx250s that has developed (again) a bit of a whirring noise. The noise only happens after the bike is thoroughly warmed up. It sounds perfect until then. This typically could take up to 20 minutes, depending on how I am riding. It does not make the noise at idle, but is evident as soon as I accelerate and stays throughout the rpm range. It is more of a whine than a tick or a grind. I mention that because the sound is in the area of the cam chain. I have already replaced the cam chain and tensioner (krieger manual now). All was good for a thousand miles or so, with only a few adjustments needed. The noise has obviously returned and no adjusting will eliminate it.

An obvious issue that will be checked on tomorrow; when I was reassembling everything, the guide to the front of the bike(opposite of the tensioner guide) seemed to sit in place. That is to say, I could pick it up and pull it right out without loosening anything. I believe it is held in place with a small metal tab held in with a bolt. I am hoping that this is the entire issue.

Has anyone had any experience with this? Is it possible that there is some greater issue lurking in the background that I need to be wary of? I appreciate the help!

 

Yeah, if it's really not a ticking or metallic sound, it doesn't sound like the cam chain. On that rubbing slider you're referring to, if I recall, one of them does seem to just sit in a slot. I don't remember a bolt-and-tab setup that retained any of the sliders, but it's been a while. I'm thinking the slider you're referring may indeed just sit in a slot, and when the cam chain is tensioned with the cams and tensioner in place, it can't go anywhere. Maybe some who've been into their engine more recently can shed more light on it.

 

Here's a pic of mine with the head off and the 300 cylinder on. The rear slider is fastened down in the case on a pivot, but this shot kind of reminds me that the front slider you're referring to didn't bolt to anything and wasn't retained by either the head or the cylinder. I just seem to recall that you fished it down into the engine case, and it rested in a slot in front of the chain. Heck...I'm even too lazy to go out to the shop and dig out the factory manual.

 

maybe you have overtightened the manual cam chain adjuster....... and the noise you are hearing is an over tight chain.

 

I'm thinking the same thing. I adjusted my tensioner once, when installing it. I didn't have to adjust it again for a couple thousand miles on the 650 when the cam chains were new and seating in, and have yet to do an adjustment on the 550. You do NOT want to have the cam drive overly tight. If it has any leverage beyond that which you generate with your fingers, it is too tight.

I'd re-adjust it cold per the instructions (available on Krieger Cam Chain Tensioners if you threw them away) and leave it at that. I doubt I'll ever do the fine tuning deal on the 550 and only do it on the 650 because if I hear the ticking the bike is usually at full operating temperature and I do the adjustment right then due to easy access and doing it while I have time to do so at the end of a ride.

Get a mechanic's stethoscope (low buck from Harbor Freight and slightly more on ebay) so you can absolutely identify where noises are coming from. I have and use one. On the cam drive there should be a sort of shushing noise able to be heard with the stethoscope, but not audible by ear. That is the cam chain sliding on the slider. Ticking would be very audible with the stethoscope and usually up by the tensioner for sure... unless it is the valves. I have two loose valves (a thou out of top spec and not worth pulling the cams to fix) on the Zephyr and can pick them out easily with the stethoscope. Amazing what can be heard with those things... besides having that kind of "knowledgeable doctor" look about you when you have them around your neck.

 

Thanks for the thoughts!

I have no illusions that I am He-Man or anything, but I backed out the tensioner all the way, and turned it until it gave any resistance at all, then backed out an 1/8. I am presently letting it warm up a good deal and will see if the noise returns.

I am onboard with getting a stethoscope too. The noise is just weird enough to absolutely warrant getting one. I will update after I give it a ride. Thanks!

 

So He-Man I may be...

I loosened the tensioner all the way (bolt was wiggly) and then tightened until it just hit the guide (not wiggly). I backed it out a smidgen and started it...low and behold I heard (for the first time ever) the ticking every one speaks of. I turned it (very slightly) to mask the ticking a touch after the bike warmed up a bit.

After a test ride, the whirring has not returned (as with these things, I will add 'yet'). If this result remains, then it can be assumed that my auto tensioner initially failed by over-tightening, causing the whirring that I assumed was a loose chain...and the return of the symptoms (which began after the weather started warming back up)was caused by my inability to rationalize what 'finger tight' means. We shall see. I can't thank you enough for the help!

 

Toldjaso!

 

... and I was thinking the noise might be from the turbo ...

 

How cool would that be! Riding along on a mild mannered 250, with the revs up a bit to be on boost, then come up on a few 650s, bang a gear on boost and launch like a rocket!

That's kind of what I experienced on a Honda CX650T - on boost, third gear, caught fourth and launched like warp speed on that closing shot of Star Trek. I tell people now I understand what is meant by warp speed!

I have a friend with a nice little turbo that would possibly work well on a 250 if he could be conned into selling it and if anyone is nuts enough to do it.