Engine Knocking Noise (w/Video)

[simmr]

Can anyone help diagnose this engine knocking noise?

Link to original page on YouTube.

I just rebuilt my engine (although, I'm still a mechanical newbie). First ride started off great, but... I got about 10 km out and the engine died as I came off the gas. Stopped on the side of the road, started it back up and would die as soon as I put it into gear. Pulled it over into a parking lot. Started up, everything seemed fine, and took off again. But then same thing, stopped and noticed a knocking noise which got worse with time. Ended up towing it back to my place.

- Someone on another forum suggested it might be a bent valve. I'll have to do a compression test. What the hell would cause a valve to bend right after a build?
- I double checked the chain this morning. Brand new chain, manual tentioner. The only thing I am certain of is the chain could not be responsible for the noise.
- Engine turns over as normal as it ever has. No knocking when I turn it over manually either.
- I didn't actually check the valve clearances again, but I will do that this afternoon.
- Drained the oil. No metal shavings found (as per someone elses suggestions).

[alex.s]

Sounds like a piston hitting the top

[simmr]

At first I thought my timing may have slipped. but I checked this morning, and timing is still right on the money.

[Motofool]

Originally Posted by simmr

At first I thought my timing may have slipped. but I checked this morning, and timing is still right on the money.

No idea, Sergio.

However, the frequency is high compared to the frequency of the exhaust; it seems to me.

If that is true, the source could be the valve trains.
Did you verify the clearances?

Welcome to the site !!!!

[Monkeytofu]

One of my valves was too loose after a recent valve adjustment and it sounded almost exactly like this.

[simmr]

I will verify them tomorrow after work. I hope that is the issue but... would that even cause it to stall out as it did? Maybe it loosened during the trip... although I think that would be unlikely. I'm pretty sure I checked my torque values.

Glad to be here!

[Monkeytofu]

Originally Posted by simmr

I will verify them tomorrow after work. I hope that is the issue but... would that even cause it to stall out as it did? Maybe it loosened during the trip... although I think that would be unlikely. I'm pretty sure I checked my torque values.

Glad to be here!

Could be two unrelated things happening at once.

[n4mwd]

I listened to the video but I didn't hear anything other than clutch basket ticking. It can come and go so you should test for that since its the easiest. The performance problem sounds more like a carb issue and may be unrelated. Hope its not serious.

[simmr]

I finally had some time:

The loud knocking sound was indeed the valve clearance. However, I'm in a bit more of a jam. The reason they were loose was because the intake camshaft melted, and unfortunately, so did the seats they sit in...

I did not know there was a difference between camshafts, but when I aligned timing to the 2T mark, I noticed (now) that the cam lobes did not match the image in the valve adjustment procedure. At 2t, instead of pointing up, they were pointing down. When I rebuilt the engine, I switched the exhaust and intake camshafts. Oddly enough, it still ran smooth at first...

Some pics I took:
http://imgur.com/a/jjICu

What I don't get is what could have caused this? Problems with oil passages? The fact that I switched the camshafts?

How do I fix this? Looks like I'll have to get a new top end?

Thanks for your help guys.

[Kevin2109]

If you WOT for 98.7798 seconds it will fix it. Careful though, 98.7799 seconds will kill it

[Motofool]

That is painful to watch, Sergio.

Proper lubrication of any bearing requires the proper gap or clearance between the parts.
Too much or not enough and the lubrication film will break apart and the metal parts will destroy each other.

Unfortunately, that is what happened to your engine.
The reasons could be improper torque of the cam covers or wrong relocation of parts that had been machined as a match (Did you use a repair manual for proper procedure?).

Yes, you need to replace the head and corresponding gaskets.
A machine shop could help you determining if the camshaft needs replacement as well.

Best!

[n4mwd]

Sadly I must concur with the others and say you need a new head. The damage is not easily repairable. But first, you need to figure out exactly why they did that. Could be clearance and could be lack of oil could be a grain of sand. Until you know for sure, you might be destroying the new heads too.

The exhaust and intake cams are identical except that the gears are bolted on differently. I'm not sure how they stack up with the clearances. They are the same part number though.

[simmr]

Thanks for your responses guys.

I did use the manual for the entire rebuild. Mind you, it's a lot to read and re-read, and every once and a while I missed something or misread it. I DID however put the camshaft covers in their right spots. This I know for sure. Switching the Intake and Exhaust shafts was a goof on my part.

I found a nice clean head including camshafts for $150CDN.

Might be a strange questions, but once I've got the old head off, is there any way to test the oil passages from the bottom block to the top? I suspect not.

Either way, I will try putting the new head on, if it happens again I might drive it into the river in a blaze of glory.

[n4mwd]

The oil gets to the head through the rubber tube on the front of the engine. Its possible that is plugged up somewhere. Maybe disconnect the tube and flush it with carb cleaner. It might also be possible to use a pump type oil can to force oil through that tube to make sure its coming out where it should.

The cam caps look similar, but they only go in one way, so you couldn't have messed that up. Also, it shouldn't make any difference which cam goes where in terms of bearing damage. The cams are identical except for where the gear gets bolted on. I strongly suspect lack of oil as the culprit.

[simmr]

I think it was debris. I hate to say it, but I remembered at one point while assembling, I noticed some flakes of metal around the area. I cleaned it off, and didn't think much of it, but now it seems like the most likely explanation. I bet you, the first time I set it (because I did it twice) something was off, scratched the surface, placed it a second time but did not clean the surface properly. LESSON LEARNED! I hope

New parts are on the way.

[alex.s]

this raises an excellent question that ive been trying to find the answer to... how to test the oil passages. maybe with the head off and the bottom filled with oil, manually turning the crank to turn the oil pump and see if oil comes out all of the feed tubes? seems like a very inaccurate test... maybe a flexible soft stick or something that can be ran through all the oil passages? this is something ive been thinking about for a few months now... still no idea on a good method

[n4mwd]

Originally Posted by alex.s

this raises an excellent question that ive been trying to find the answer to... how to test the oil passages. maybe with the head off and the bottom filled with oil, manually turning the crank to turn the oil pump and see if oil comes out all of the feed tubes? seems like a very inaccurate test... maybe a flexible soft stick or something that can be ran through all the oil passages? this is something ive been thinking about for a few months now... still no idea on a good method

The oil goes through the filter and then up the hollow bolt into the oil delivery system. It might be possible to get a pipe with the right thread and artificially feed the system with pressurized oil. That way you could just watch to see where it comes out.

As far as debris, it would have to be in the oil passages somewhere. Just being in the crankcase isn't going to mess anything up (unless there is a ton of it) because it gets stuck in the filter.