Rattle, cam chain? Suggestions please

[Jon M]

My '78 XS650 has a rattle that sounds like valves but they are adjusted correctly. I've checked the cam chain tension and it seems to make no difference. The rattle is louder when the engine is hot, maybe just because the oil is thinner. It's most noticeable when the engine is not under load. I think it is very slowly getting louder (over the months I mean) and I plan to do some longer trips this year so I figured it was time to resolve it.

I deduced that it was the front cam chain guide so pulled the engine. The front guide looks fine, in fact I think the PO already replaced it - he told me he rebuilt the engine about 15,000km ago but I'm not sure exactly what he did.

The rear tensioner/guide looks ok but the rubber part is quite grooved. Is this a problem? Also, is there a way to tell if the cam chain needs replacing - could a slack cam chain be the source of the rattle? I'm not sure if it's the original chain - the links are stamped with 'Japan' and 'EK29 H' - anyone know if this is OEM?

There is a small amount of metal in the oil - seems to be sticking to the magnet.

Any suggestions on what else I could check re the rattle while I'm in here?

Thanks!

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[Jon M]

Actually I should add that the rattle is somewhat irregular, so I don't think it's a valve thing, but I'm not sure that my logic is sound on that.

I know these engines aren't silent by any means but it just doesn't sound right.

 

[Brian902]

Keep going, remove clutch cover and sump cover.

Your investigation is not over yet.

Listen to videos here of other engines.

They don't have rattles that come and go.

 

[retiredgentleman]

I think you're being overly cautious here. These engines are not quiet like modern engines.
They all make some mechanical noises.

Make sure you use 20W50 motorcycle oil. I have found that oils such as 15W40 make the engine noisey. The thicker oil works better.

I used to use 0.004" and 0.006" for the valve clearances, but a few years ago I changed over to 0.003" and 0.005", for a little quieter operation.

A small amount of black (metal) sludge, attached to the magnets, is just normal wear particles.

 

[Jon M]

I don't think I'm being overly cautious. It's an extra noise, additional the normal running chatter and it's somewhat irregular, like something rattling about. Not a constant ticking/tapping. High pitched, like a pinging almost. A bit like a ball bearing bouncing about in the engine.

I'm using 20w50. The noise is only really audible when the engine is hot.

It sounds like it's coming from the top end, central, possibly a little louder on the left.

I've listened to a bunch of the videos, but so far I can't pinpoint it - it sounds most like a cam chain noise but it all looks fine in here. I am kicking myself for not thinking to video my engine before I pulled it from the bike!

I'm going to check the valve adjustment surfaces and then the pistons for weird wear, then I'll see if I can detect any movement in the wrist pins.

 

[5twins]

Your front guide does look new (or newer), but check it anyway once the jugs are off. On old ones, the rubber strip starts to come unglued. That loose section can randomly slap against the base while running and cause some noise. Mine was worse during about the first 30 seconds or minute after starting .....

Yours appears to have an EK brand chain. My '78 had a D.I.D. I know Yamaha also used Tsubaki chains. I never heard of them using EK chains but I suppose it's possible, like if they couldn't get the D.I.D. or Tsubaki. Most likely, yours is a replacement. How loose was it? Did you cut it to remove the cam or just slip it out from under the chain? If you slipped it out and were able to do it with the bearings still on the cam, that chain is badly stretched.

 

[retiredgentleman]

Here is another thing to check on, for top end rattles.

The camchain tensioner should have a "damper". It was missing on my bike...............some PO thought it wasn't needed

I believe the OEM was rubber, but I replaced it with a copper washer, which works quite well.

 

[Jon M]

Thanks guys.

I added one of those metal/rubber tensioner dampers a while back but it made no difference.

To remove the cam I removed the bearings and slipped the cam out from the chain. It was tight so I'm becoming more convinced that the chain has been replaced already and is fine.

The fact that the noise gets worse when the engine is hot suggests (I think) that the valves aren't the issue as they tend to expand and get tighter with heat. So I guess I'll have a look at the wrist pins and pistons next. The bike has really good compression (about 150lbs IIRC) and I have a feeling that the PO put in new rings when he rebuilt it - he mentioned something about Nissan rings fitting. Maybe he reused the wrist pins and one of them has a bit of play now. I'll see if I can detect any movement in them and check with calipers to see if they are within spec.

I have a manual but even so all tips are welcome - this is my first time inside an engine since rebuilding my old Lambretta 150 about 25 years ago!

 

[schlakeandbake308]

Did you ever solve this bud? I'm running into an identical issue, mine is freshly rebuilt

 

[TwoManyXS1Bs]

Hey, Schlake. Yes, he continues the saga in this thread:

http://www.xs650.com/forum/showthread.php?t=39744

 

[TimothyMoore]

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