Greetings fellers, first post!

Been lurking and reading and would first like to say thanks for all the good info up here... learned a lot to get my SF going.

Bill Blue 351, mega bomb, Q4, DJ128 / 35 / 2-1/2 , cover on but extra holes added, Krieger tensioner,

I've got a mechanical background but this is my first bike and I'm stressing myself out over engine noises. I've got a tick/tack/clack that directly corresponds to engine rpm and can occur all over the rpm range. It's particularly bad at heavy throttle, definitely noticeable at idle, and seems to go away at very light throttle and on over-run. I can't guarantee that the idle clack clack and the heavy throttle clack clack are even the same noise but they kind of seem to be.

It's not the cam chain - I've been all through that. It's not the KACR, which is completely removed. I've put the stethoscope to it, but it seems inconclusive... perhaps near the exhaust valves, but I can hear it throughout the engine. Tried to check valve clearance, but accidentally bought too-thick feeler gauge set. I'm hoping for an exhaust leak and have a new ring seal on the way, but I sure can't feel any leaking.

So after all that, I guess my question is - what is a "normal" amount of noise? I've seen mention of "box of rocks", concrete mixer, shrapnel in a pot, etc... It's not like that, but it is a very definite, very audible clack-clack-clack. If my WRX were making that noise I'd freak right the hell out, but maybe these things just make some noise and I should get over it? Would any of you care to tackle a bit of expository writing to carefully describe the song of a properly running KLX?

Thanks!
ZB

 

I've had a lot of bikes, and when everything is working properly, I don't think the KLX engine is noisy by nature. The valve adjustment issue definitely needs to be removed as a possibility, and your suggestion of the exhaust header gasket is plausible. See if the noise is present after addressing those two items. Oh...and double check the header/muffler joint.

 

When everything is working right, the engine is nearly silent. I have 4500 miles on mine and it is smooth running. The transmission has always been a piece of **** though, false neutrals and false bottom gear. Trans is still quiet.

 

About the noise - Since new or a certain mileage? Did it show up after any changes? Gradual or suddenly clicking?

 

I have had a rocks in a coffee can clatter between 5-7000rpms since new, now at 2500 kms, and I installed the cam chain tensioner as instructed to no avail.

And in response to the other fellow's post, the trans on mine seems to be a real POS too.. quiet but getting stuck in neutral at times.

Anywho, let me know what you discover. I'll be following this thread.

 

Well, I checked valve clearances, replaced the exhaust seal ring at the head, checked the timing chain tension again, and nothing changes the noise.

Bike has just under 2,000 miles on it with about 1,000 of that on the 351. Unfortunately, I can't really say if the noise it new or not. I'm so new to this myself that I've been mainly busy trying to ride safely and had not been paying particularly close attention.

Anyway, I feel like the ticking/light clacking at neutral is probably an exhaust valve since the stethoscope seems to lead there, and it is set pretty close to maximum clearance.

As far as the other noise, it's only present when giving the bike a pretty good bit of hard throttle... accelerating hard or climbing. At light to moderate throttle it sounds fantastic - no clattering or clicking or anything. To further describe it, it *almost* sounds like the sharp rap you would hear with open exhaust... it's one 'clack' per power stroke.... the clack happens in time with the pulsing of the exhaust note. I'm really hoping that all I am hearing is just the sounds of a highly compressed fuel/air mixture suddenly igniting right between my legs. LOL. Please tell me this isn't piston slap on my brand new big bore!

As far as the shifting, I had Valvoline 10w-40 in the bike and switched to Rotella 15W-40 based on reading here. That smoothed my shifting very noticeably.

Thanks guys, I guess I'll just ride it until something blows up. It's been doing this for at least 500 miles and doesn't seem to be getting any worse.

 

Does it sound like it is coming from the left side? Just a possibility, it could be chain slap. Not the cam chain the main chain. Mine will throw the chain of the front sprocket and it hits the chain guard when the engine lugs (too low of RPM vs Speed/accelerating). I have the 13 tooth front and it does it more than it would with the 14 due to the smaller diameter. My WR426 did this a lot and it was consistent with every power stroke like you mentioned.

 

Hmmm.... I did put a 15T on it and that is one thing I've not fooled with yet while noise hunting. I'll check into that at lunch today, thanks.

 

Since the OP said it definitely also occurs at idle, I'm thinking the sprocket/chain noise wouldn't be a factor at idle. Still has some of the classic cam chain symptoms, but who knows. Are we sure that the tensioner is adjusted properly?

 

He also said " I can't guarantee that the idle clack clack and the heavy throttle clack clack are even the same noise but they kind of seem to be."

So he might have two different problems going on.