I've made a huge mistake

[mslot84]

I had my valves replaced and shimmed professionally, however, when I re-installed the top end I lined up the cam facing to the back.  This is correct if it's at TDC of the compression stroke...but I now believe I was lined up on the exhaust stroke (It seemed to be right at the tipping point when I spun the flywheel).  I have done 4 rides since and have recently noticed some engine noise that I haven't heard before (metal ticking)...also the idle skips and has started to kill on me when idling.  I don't have any metal shavings in the filter or oil...the valves are still in spec.  I pulled off the timing chain and flipped the cam.  I put it all back together and started it.  It seems to idle much better now but I still have what sounds like excess engine noise.  Any idea what kind of damage I may have done?  Help!

[MX450R]

I would think if the damaged was caused by being out of time then it would have been instant, not take 4 rides to show up. I would triple check everything to make sure nothing is working lose. Can ya tell where the noise is coming from at all?

[pomoco]

I'd get a mechanics stethoscope and listen to the engine at different spots to determine where its the loudest. The timing chain tensioner has been reported to be a common issue. I agree with mx450r. If you had it out of time it would have damaged it immediately. It ran good for 3 rides? Strong as ever? Is the noise definitely new? Sometimes I'll ride mine without a helmet just to the truck or something and it'll sound a lot noisier. If its idling low or weird the engine will usually make more noise. Does the noise speed up when you rev it or does it go away off idle?

[jrhonda]

Most likely valve to piston contact

I'm surprised that you did 4 rides

[MX450R]

Most likely valve to piston contact

I'm surprised that you did 4 rides

it wouldn't have lasted 4 rides if the valve was hitting the piston

[CRF rider]

A worn out cam chain? That's my first thought. Slack in the chain could cause noise, and it could jump time and cause damage down the road.

 

If it was a loud ticking from day one, a shim could have fallen out?  

[Shawn_Mc]

Could be a couple things. Could be the cam chain flopping around because the OEM auto tensioner is a piece of shit (I refuse to pull that punch), could also be paranoia...believe it or not. The CRF engine makes a ton of racket even when its perfect. Or, it could be the left side main bearing on the crank. Which happens more than I care to elaborate on.

 

If you get a piston into the valves, its game over. If you miss the timing, it'll still run, not as well, but better than you'd imagine it should. I think you missed the timing the first time, or the shop did. Its pretty damn easy to do, especially if you follow the damn service manuals directions. The amount of info that isnt in the manual is a problem all by itself.

 

If a shim fell out, it'd have to the exhaust side and it'd be obvious the second the valve cover was removed.

[mslot84]

Could be a couple things. Could be the cam chain flopping around because the OEM auto tensioner is a piece of shit (I refuse to pull that punch), could also be paranoia...believe it or not. The CRF engine makes a ton of racket even when its perfect. Or, it could be the left side main bearing on the crank. Which happens more than I care to elaborate on.

 

If you get a piston into the valves, its game over. If you miss the timing, it'll still run, not as well, but better than you'd imagine it should. I think you missed the timing the first time, or the shop did. Its pretty damn easy to do, especially if you follow the damn service manuals directions. The amount of info that isnt in the manual is a problem all by itself.

 

If a shim fell out, it'd have to the exhaust side and it'd be obvious the second the valve cover was removed.

I discovered that the timing is not the issue, I'm almost positive.  I was getting wrapped up in whether it was the exhaust of compression stroke...the truth is it doesn't matter as long as all the timing lines and dots align with each other (sparks on both strokes).  To your points above, I pulled the chain tensioner and it appears to be working properly.  Are you suggesting the OEM spring isn't strong enough to hold the chain tight?  The sound does seem like it's coming from this area.  I changed the spark plug, that wasn't it.    

The knock is sporadic not a constant knock, but when it idles low it's louder and seems like it causes the idle to miss every few seconds and then will kill the motor sometimes when idling low.  While revving the knock seems to go away mostly, when I adjust the idle high the knocking is not as loud.  I took the head cover off and it all seems to be in good order...tolerances are still in spec. 

[mslot84]

I'd get a mechanics stethoscope and listen to the engine at different spots to determine where its the loudest. The timing chain tensioner has been reported to be a common issue. I agree with mx450r. If you had it out of time it would have damaged it immediately. It ran good for 3 rides? Strong as ever? Is the noise definitely new? Sometimes I'll ride mine without a helmet just to the truck or something and it'll sound a lot noisier. If its idling low or weird the engine will usually make more noise. Does the noise speed up when you rev it or does it go away off idle?

Thanks.  I have checked the tensioner and it seemed to have ok spring.  When I press on the chain it isn't tight by any means, but it doesn't seem too loose.  I have actually ridden more like 6 times...no lack of power (other than what my dented header pipe would cause).  Noise is definitely new, at least at this volume.  It does sound like the noise is coming from the front / top of the motor on the right side.  It is not a constant knock but comes in and out and is louder when idling low.  When I rev the motor it almost goes away completely.  If I turn the motor over slowly I can hear a quiet tick that I believe is more than just the valves opening...I believe this is the louder sound when the motor is idling. 

[pomoco]

I'm no expert, but I'd imagine the auto decompression will make a little noise when you turn it over slow and its on the top right side. If I was you I'd probably get a manual can chain tensioner and if you don't already have one, an r&d remote fuel screw. If its not dialed in, the poor mixture at idle could make the engine rattle a little more than normal.

[Zondebok]

My 08 is noisy at idle, but sounds OK even a little above idle.  I was worried about it, but have been convinced not to be, and it has worked out fine ?

Edited May 29, 2015 by Zondebok

[Rocksalt]

Sounds like the piston needs replacing.

 

When you check the cam chain tension see how tight it is when moving the chain left to right on the sprocket. It should resist a little moving left to right. A more detailed way to check it is to remove the flywheel and push on the kickstarter. Then look at the right side of the crankshaft for the chain being loose on the return side. signs the chain WAS too loose is to remove the piece that stops the chain from dropping off the crank for damage. It's the piece that holds the oil pump in and secures the grommet.

 

There is no such thing as the timing being 180° off as mentioned. The cam position determines what stroke the engine is on and if the cam was installed 180 off it would be hard to put the bolts in the cam tower as the lobes would be pushing down on the valves.

[jrhonda]

Sounds like the piston needs replacing.

When you check the cam chain tension see how tight it is when moving the chain left to right on the sprocket. It should resist a little moving left to right. A more detailed way to check it is to remove the flywheel and push on the kickstarter. Then look at the right side of the crankshaft for the chain being loose on the return side. signs the chain WAS too loose is to remove the piece that stops the chain from dropping off the crank for damage. It's the piece that holds the oil pump in and secures the grommet.

There is no such thing as the timing being 180° off as mentioned. The cam position determines what stroke the engine is on and if the cam was installed 180 off it would be hard to put the bolts in the cam tower as the lobes would be pushing down on the valves.

^^^^ agree