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Discussion Starter · #1 ·
07 zx10r with about 30k miles

Engine ran beautiful, going to work and get off the freeway. At the light the engine just all the sudden starts to knock, very loud. I shut it off and roll it to a parking lot


Tow bike home. Wanted to start it up and see where noise was coming from and did, it was knocking pretty bad and got worse when I revved it to like 2-3k.
drained oil, no shavings. Not 100% sure this is a rod knock since it suddenly happened at idle.

Seems to me like something internally let go. Engine starts right up.
Im not sure how to go about this. What should I inspect first, is there any common problems or any other people that have had similar issue.


Im thinking of just dropping the engine since its so tight in the area, I want to inspect the valves and piston and the bore.
 

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First, :welcome: Taizer. Start a welcome thread in the newbies section so people won't clutter up this one with the welcomes. Using this thread for welcomes may make this thread convoluted and hard for the people to follow and help you out.

Second, I'm almost sure someone here has had an issue similar to yours and will chime in.
 

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Discussion Starter · #4 ·
Disassemble and inspect.... no way around it.
this is true and this is not a simple process for me as i work on cars and never worked on bikes too much. So far i have taken all the covers off and inspected the spark plugs, clutch basket, starter, and flywheel area timing chain.
The timing chain is tight, has almost no slack. Dont know if this is normal or not but I checked from below.
Engine spins pretty good.

I think Ill be taking the oil pan off next as I do not think this motor jumped timing. Also going to try to grab a borescope
 

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If you have the valve covers off you should be able to see the timing marks from there, as well as the crank cover. Also I would look for the service manual for the 2nd gen as that will help a lot with tolerances. I also am pretty sure there is a link somewhere on this forum to the service manual.

Oh and welcome!!
 

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Depending on how loud the "knock" is, I'm going with a spun rod bearing as the culprit. I spun my G4 rod bearing just off idle. Idle is the point of the lowest oil pressure and the bearing can fail at that point - instant knock. I find it hard to believe that piston slap would be the culprit. If you dropped a valve, the engine won't be knocking, it will be misfiring and running piss-poor due to the cylinder having no compression essentially. It may also be a broken clutch basket that's hitting the inside of the case.

First thing to do is pull the oil pan and look for fragments. Next would be to pull the clutch cover. If those look good, then look at the top end.
 

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ok thanks for all the replies. Checked the intake valves they all look good from the intake chamber, but I know exhaust are more prone to fail from my experience.
Just looking at them like that won't tell you anything, you need to remove the valve cover and use a feeler gauge to check the clearance between the camshaft and bucket.

Also as sky said check the clutch basket. I've heard of that a few times on here.
 

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Discussion Starter · #13 ·
Depending on how loud the "knock" is, I'm going with a spun rod bearing as the culprit. I spun my G4 rod bearing just off idle. Idle is the point of the lowest oil pressure and the bearing can fail at that point - instant knock. I find it hard to believe that piston slap would be the culprit. If you dropped a valve, the engine won't be knocking, it will be misfiring and running piss-poor due to the cylinder having no compression essentially. It may also be a broken clutch basket that's hitting the inside of the case.

First thing to do is pull the oil pan and look for fragments. Next would be to pull the clutch cover. If those look good, then look at the top end.
well so far drained oil under strain and really didn't see one fragment of bearing or any metals. I mean it still could be a spun bearing.

And about the valve dropping It happened instantly so I never noticed power loss or anything shut it right down. But before the incident the motor ran unbelievably good.

Clutch basket is also good. Took cover off and clutch plates all look good, no sign of any clearance issues or fragments.
 

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Discussion Starter · #14 ·
Just looking at them like that won't tell you anything, you need to remove the valve cover and use a feeler gauge to check the clearance between the camshaft and bucket.

Also as sky said check the clutch basket. I've heard of that a few times on here.
True but knocking would indicate a visibly bent valve, not just a leaking valve. I mean its no a ticking type of deal its a really loud knock. I tried getting a video but didnt hit record lol, oily hands. Now I cant really get a video because drained oil and coolant.
Best bet is checking cylinder leakage I think.

I would drain the oil to look for any shiny stuff floating around. If you do then that's not good
Already posted no metal shaving or any contamination in oil or coolant and no fragments in any engine covers.
 

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True but knocking would indicate a visibly bent valve, not just a leaking valve. I mean its no a ticking type of deal its a really loud knock. I tried getting a video but didnt hit record lol, oily hands. Now I cant really get a video because drained oil and coolant.

Best bet is checking cylinder leakage I think.







Already posted no metal shaving or any contamination in oil or coolant and no fragments in any engine covers.

Just looking at the oil is not conclusive. I couldn't see anything in my oil either. The bearing fragments are big, heavy, and the oil drain passage outside the pan has a lot of nooks to trap the fragments. From your description, everything sounds like a rod bearing pounding the crank. Exactly what I've experienced.

If you bent a valve, that cylinder won't hold compression or fire because the valve would not seal. The engine would knock a bit, but the sound of it running on 3 cylinders would drown it out. Plus once the valve is flattened in the cylinder (if it doesn't lock the motor) the noise will decrease.

Drop the oil pan.

Auto part Metal Engine Pipe Steel
Auto part Engine Automotive engine part Pipe Carburetor
 

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Discussion Starter · #16 ·
Just looking at the oil is not conclusive. I couldn't see anything in my oil either. The bearing fragments are big, heavy, and the oil drain passage outside the pan has a lot of nooks to trap the fragments. From your description, everything sounds like a rod bearing pounding the crank. Exactly what I've experienced.

If you bent a valve, that cylinder won't hold compression or fire because the valve would not seal. The engine would knock a bit, but the sound of it running on 3 cylinders would drown it out. Plus once the valve is flattened in the cylinder (if it doesn't lock the motor) the noise will decrease.

Drop the oil pan.

View attachment 380505 View attachment 380513
ok thanks for the reply. Ill drop the oil pan tonight see if their is any fragments.
As far as the first rod closest to flywheel. cylinder 1 I assume the rod has a little play about half a millimeter when moving side to side.

Also I see you had this problem how did you fix it and did you need to buy a new crank or have it resurfaced/polished.
 

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ok thanks for the reply. Ill drop the oil pan tonight see if their is any fragments.

As far as the first rod closest to flywheel. cylinder 1 I assume the rod has a little play about half a millimeter when moving side to side.



Also I see you had this problem how did you fix it and did you need to buy a new crank or have it resurfaced/polished.

The flywheel is on the right side as part of the clutch basket. That would be the number 4 cylinder. The rod will wiggle ever so slightly side to side. Enough to feel, but not much more. The number 1 cylinder is on the left side of the motor.

I got my crank repaired by APE in California. Did great work and upgraded it with fluted oil passages and lightening. Cost almost as much as a new crank and took several months though. And I needed a LOT of other stuff to rebuild the motor. I hope I'm wrong on your diagnosis, as it's a big expensive job.
 

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Discussion Starter · #18 ·
The flywheel is on the right side as part of the clutch basket. That would be the number 4 cylinder. The rod will wiggle ever so slightly side to side. Enough to feel, but not much more. The number 1 cylinder is on the left side of the motor.

I got my crank repaired by APE in California. Did great work and upgraded it with fluted oil passages and lightening. Cost almost as much as a new crank and took several months though. And I needed a LOT of other stuff to rebuild the motor. I hope I'm wrong on your diagnosis, as it's a big expensive job.
Ok I got it.

As far as spinning rods Ive spun rods in my turbo civic few times but not nearly as loud. Always just micro polished and new bearings good to go as long as rods didn't see too much heat/discoloration and crank still smooth.

My leakdown tester does not fit, spark plug threads are to fine and smaller diameter.
 

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Ok I got it.



As far as spinning rods Ive spun rods in my turbo civic few times but not nearly as loud. Always just micro polished and new bearings good to go as long as rods didn't see too much heat/discoloration and crank still smooth.



My leakdown tester does not fit, spark plug threads are to fine and smaller diameter.

There are no over sized bearings available for the rods. You have to weld the crank journal up to spec so you can grind it back down. You only get 3 OEM choices and there aren't any aftermarket ones. That's why the repair is more involved on bike motors. Especially since they spin to almost 14k revs. There are very limited options for upgraded connecting rods as well.

I needed 4 new rods (1 bent others out off round), New bearings, head checked (since the piston hit the head slightly), New oil pump, New pick up, New gaskets, and a bunch of miscellaneous crap. And keep in mind that I spun the bearing just of idle at about 3-4000 rpm before I shut it down. Not pretty.
 

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Discussion Starter · #20 ·
Ok took oil pan off. Oil looked brand new not even a spec of bearing or any metal in it. Tried moving the rods and it seems all the rods move slightly side to side but not alot. I'd say since there were no flakes in the oil and rods all move side to side pretty consistently with each other that the bottom end is fine. That's just my opinion for now.
Everything I looked at from below looked great. Very frustrating not getting any visual feedback but also rules out a lot of expensive stuff. I hope the crank is fine and the rods. If I need to swap heads that would be great.


I think next step is leakdown test valvecover, and cylinder head removal.

Also from your opinion a loud knock would be a very distinct movement in the rods as far as side to side and up and down. Would you agree.
 
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