Engine Clatter - What is it likely to be?

gene xs

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My new to me 1981 XS650H. I got the choke detent balls fixed using a Zerk fitting ball and spring (thanks to the forum and Gary for the steer). Took it out for a short ride yesterday and noticed a clatter in the engine. The valves are right on spec and the cam chain tensioner is adjusted correctly, but there is a pretty noisy clatter in the engine. It's not present at all in my '78. I took a short video that has the sound. It's at

I have my own idea of what's clattering, but don't want to be prejudicial.

The PO said that the engine has 6k miles (it's not the original engine). Since I haven't been inside the engine, I have no idea if that's accurate.

I had hoped to be able to flip the bike without getting inside of the engine, but that might not be an option. Luckily I only paid $800 for it and only have about $250 more in it thus far.

The best laid plans of mice and men....
 
Since it's 100% sure the valves are adjusted right....
What weight of oil are you using? The lighter the oil the more noise. 20w50 seems about optimal to me. Remove a valve cover and if a strong oil mist comes out, oil is getting to the top. Could be loose fitting rod upper or lower end. Could possibly be rings slapping in the grooves. What is the compression of the motor? That's usually a rough indication of wear throughout. Also screw the valve adjusters all the way out and look for pitting on the ends that would keep them from being adjusted right.
 
The valve tips and adjuster ends tend to pit, the feeler bridges the pitting, clearance checks as right, but when pits line up it there's a bigger gap. No easy answer to this problem.
 
If that is one of the problems, in my experience with my own '81 it was the adjusters pitted and not the valve tips. The easy VW drop-in replacement from Autozone isn't something they carry anymore. I've been using XS Performance adjusters and they seem okay. They pass 2M's file test.

It seems like somebody offered some suggestions about adjusting with pitted valve tips, but I'm not sure. You could tighten the adjustment almost to nothing and see if the noise goes away to eliminate it as the problem. Don't run it for long that way though.
 
Try checking and adjusting the cam chain tension while the engine sits there idling. It's very easy to screw up the static adjustment method (motor off) outlined in the manuals and get the chain set too loose. Then the motor can tick like the valves are loose.
 
Yup - sounds like something to do with the timing chain to me as well. You may (if you are unlucky) have a failed front timing chain guide. There is no option but to replace it if that is the case.

Check out my thread entitled "Lucille pulls another one on me" - it tells the full saga of timing chain guide difficulties. Here is a linky:

http://www.xs650.com/threads/lucille-pulls-another-one-on-me.52694/

It is not particularly expensive or difficult to fix - but it would require pulling the engine and at least the head cover (the portion with the rocker arms and rocker shafts) if not the head itself. As long as your compression is good (say....130-150 psi or better on both sides) then you could get away without doing anything inside the cylinder bores themselves, IMO.

Pete
 
I have no idea what oil is in it. It was put in by the PO and looked very clean. Compression is good. I forget the numbers, but it was the same as my '81 - plus the engine is strong.

I will check the adjusters and valve tips for pitting and readjust the cam chain tensioner - this time with the engine running. If I don't find joy, the engine will have to come out. BTW, I did put a mechanics stethoscope on each valve cover and did not hear anything. I will do the same with the cam chain area.

The noise does sound a lot like valve ticking but is much much loader than I would expect (I used to own a BMW airhead - they are famous for loud valves). My hunch is that the cam chain tensioner has gone south. We will see...
 
Be a good idea to drain the oil, pull the sump plate off and check for black plastic bits. Could be the guide lost some weight and now its riding on aluminum. Shavings would show up in sump and side filter too.
 
Yup - if the guide is going you will likely find long pieces of stiff black plastic (i.e NOT magnetic) in the sump. Something about the size of typical toothpick...:yikes:
 
To read valve clearance with pitted valve stem, set up a dial indicator or dial test indicator on the rocker arm and wiggle same.
 
Sounds like we could use a "mechanics stethoscope" thread. Where to probe, where not to probe, likely causes. A sound recording attachment on the probe during video. Bad sounds, good sounds, ignorable sounds. I'd be up for that, but don't have a stable of 'noisy' bikes...
 
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