Jump to content
Sign in to follow this  

left side engine noises, popping like a chain skipping over teeth.

Recommended Posts

After a recent race, I started hearing a popping noise, much like a sprocket with the teeth broken off, on the left side of the engine. More pronounced when under a load.

Got her home, and timing was dead on, but cams a bit tight, so reshimmed all for to be perfect. Changed the oil (do it every 5 hours on the hour meter), pput her back together, and same thing. Checked both side cases for shavings or metal chunks, but looked perfect.

Pulled the rekluse off, and looked fine with everything nice and tight.

Starting to wonder about the timing chain. The bike is a 2009, with 78 hours, on its second top end. I baby it pretty well. I rechecked the timing, and its dead on still, and checked the tensioner, and it seems to be working. It starts right away, no loss of power or backfiring. Plug looks perfect.

Going to pull the cylinder now, oh joy, and look at the sliders and chain, but dont know how i tell if the chain is borked, or the tensioner.

Ideas gang?

Share this post


Link to post
Share on other sites

The sound you hear could be a timing chain kink making the rounds inside, and/or the sliders jumping from the kink as it goes around. You may not have jumped time, but why chance it? You wont see it around the cam sprockets. Try to pull the chain up from the cam sprockets under tension. (Just remove the valve cover) Does it have alot of play when pulled off the cam sprocket? It should have none at all. Take the chain out of the engine and lay it flat. Does it feel stiff in kinks? Check the chain buffer in the valve cover. Is it retracted at all? Does it show a lot of rubbing? Or no rubbing at all?

Did you check the sprocket on the crankshaft end? Make sure there is no missing teeth. Check the guard that is down near the oil pump cover, left side. Make sure it is not gouged or bent, or looks like the chain rubbed or hit it at all? That means the chain is slapping at points.

At 78 hours, that is alot for the chain at this point. Actually, even thought I am giving you a bunch of time wasters for checking it, just replace it at 78 hours.

Change it after checking the crankshaft end timing sprocket, and the sliders and tensioner.

Only a 120 dollar piece of mind.

I hope it actually has not been jumping back and forth on you, as you have been riding.

The durability of a modern four stroke all hinges on one thing, valve train health. The whole valve train should be checked every chance you can or get. I dont mean a full tear down. There are simple measurements (like valve clearance) for the chain, tensioner and sliders you can do. You dont even have to drain the oil. I change my timing chain and tensioner every season. Plus, the tensioners are known to fail from wear.

Share this post


Link to post
Share on other sites

After taking your advice, tore whole top end apart, replaced the timing chain and the alignment bracket..... no change.

Still sounds like rocks in a chain going thru a sprocket, more so under a load and with speed. but no sounds when engine is off and rolling the wheels, or when in gear pushing it around.... i tried putting more pressure on the auto adjuster, and didnt seem to elicit a change. Im pretty stumped, and just am trying to avoid spliting the cases....

Share this post


Link to post
Share on other sites
Plus, the tensioners are known to fail from wear.
What kind of cam chain tensioner failures have you seen or heard about? Earlier this year I pulled mine apart, and didn't see any significant wear so I (reset it and) put it back on.
Im pretty stumped, and just am trying to avoid spliting the cases....
This might sound dumb, but you could try a new chain and sprockets. I'm just thinking maybe some uneven wear causing some irregular engine loading thru the transmission. Pretty wild guess, but hey.

Share this post


Link to post
Share on other sites

Damn, if not top end, and it does it in neutral, then there's only a few other parts moving. When the cylinder was off, did you check the rod big end run out, and feel for any play in the main bearings? Any unusual particles in the drained oil or used filter?

Share this post


Link to post
Share on other sites

Yep, checked it all, everything seemed brand new. Even cleaned the internal filter, just had the silicon worm, no particles on it. Use a PC SS filter, looked pretty good, but cleaned it out as well, I clean it every 5-6 hours with every oil change. Makes no noises when you rotate the wheels, even in gear, but it does have a z-pro rekluse, so I might return the factory clutch to see if I can recreate the noise with out the motor running.

Share this post


Link to post
Share on other sites

After all that has been done the problem is most likely the main bearings. You can remove the flywheel and balance shaft sprocket and just barley see the cage of the main bearing. If the cage is distorted at any point the balls will rattle around on the races and... well you know. Once you get it torn down to that point and need help inspecting just ask.

If you can do your own top end, the bottom is not much more difficult, just time consuming.

Share this post


Link to post
Share on other sites

Mine had a strange noise when running and the wrist pin was split in two. The bike never did quit running - just made noise. Your wrist pin was good? You took the piston off the rod?

Share this post


Link to post
Share on other sites

Splitting the cases isn't hard, just time consuming... but it seems that's where I'm heading. Played with it today, manually putting more tension on the timing chain, no difference as far as the noise. Will check out the wrist pin for sure, but is fairly fresh top end, from Vertex. Will let you guys know the skinny, thanks for all the ideas.

Was weird that the retainer at the base of the timing chain was bent a little though, but could be vibrations from the main bearings letting the crank move a little sloppy I guess. Sure felt perfect though... /shrug.

Share this post


Link to post
Share on other sites

Found the issue, the 28 tooth low trans gear only had 27 teeth... Bad thing is I don't see the missing tooth anywhere... The 2012 has a 2.3 mm wider gear, guess this might be a common problem.

Share this post


Link to post
Share on other sites

Glad you found it! Deff. a new one by me, I have not heard of this problem before you. Check in the secondary oil pump pick up for debris. (the one in the center of the cases) You may find your missing pieces.

Share this post


Link to post
Share on other sites

Sorry, have not been on.

Sorry to hear it was a trans gear. I was hoping it was not.

That would have been my next guess, as any sound like that means sproket or gear.

Numroe,

My chain tensioner on my 2008, the stock first unit, did fail at 45 hours. I could release it, and push it in my hand while shaking it and it will push back in by a skip of two steps of the screw.

The spring wears, and after a small step back and forth while running will round the screw edges down.

Others have had this, some years less or more. I think it may have been a batch out.

No problem since changing it. I want a std non-auto one, but have to wait on that right now...

Share this post


Link to post
Share on other sites

Thanks JA. I'll pull my tensioner off and have a closer look at it.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...