Top end valve sound got me concerned

[Dangitdan]

Good evening guys. I am here looking for some advice.

bought this 83 xs650 from an older gentleman. He was the second owner from 87 all the way till now and he was a racer and mechanic. The bike have about 70k miles on it and never needed a engine rebuild. I rode it home and damn this is really a peak example of a survivor, runs so fucking good.

enjoyed myself for about a month or so. one day I went for a 2 hour trip and when I got back home I started to hear small tacking noises on the top end. It sounds like it comes from valves or rocker arms. I got nervous and adjusted cam chain and valve gap the very next day. The sound was still there.

Oh no. What is going on? Bike still runs fine and I don't feel like there is anything bad. So i went online and saw some people say that its normal some say its not some say its cam chain guide but I really don't think it is.

So a month ago I decide to pull the top end off. drained the oil, smells like clutch and sparks like the stars in the sky (pray it's just the clutch material). pulled the engine, got the cam cover and cylinder head off. I don't see anything that is obviously abnormal. So i wish to ask you guys for some advice.

There are some pictures of the rocker arms and cam cover.

 

[Dangitdan]

Here are some picture of the oil passage block off. they are blocked off as they should but there are quite some debris on them. took one piece of the gunk off and it doesn't seem like it reacts to magnets. is this something concerning?

 

[Jim]

The factory smeared a small bit of some sort of epoxy on the block-offs. I suspect that's what you're seeing. Not really a problem. You can clean that block-off real good with solvent and apply a dab of J B Weld original formula on it and you'll be as good as new.

 

[Dangitdan]

big relief wow. thanks man. i will put my JB weld on my buying list

 

[Jim]

When I say solvent, I mean something strong like acetone.
Scrub it with a wire brush, wash with solvent and apply the J B immediately after the solvent evaporates. That'll be your best bet for good adhesion.

 

[Dangitdan]

adding acetone to amazon shopping cart........

 

[gggGary]

following, can we see the cam lobes?

 

[Its been a long time]

And drop the oil sump plate off and see what's in there too?

 

[gggGary]

While we're at it pics of; pistons, bores, plugs, and cylinder head.
Are all the rocker arms moving freely?
So far from your pics my only take-away is it looks like it's been running pretty hot, that amber color coating surfaces.

Head cover from a higher miles motor on my bench. High compression 750 but with an oil filter and cooler. Please excuse the dirt.


Are those the mufflers that were on it when you got it? carbs been jetted up a bit? BS34's come borderline lean from the factory. A freer flowing exhaust needs jetting changes to match.
There's a theme in XS-dom "It ran fine til I took it out for a long highway run."

 

[Bob Wegman]

I would remove the rocker arms and check the shafts they ride on. That engine doesn't look like it had too many oil changes. I would check that the oil passages in the rockers shafts are clear.
After I look at those pictures again, I think the cover looks pretty darn good considering it has never been apart. Best of luck with your project.

 

[gggGary]

pps failure is pretty rare but check your valve springs?

 

[jetmechmarty]

What does the front cam chain guide look like? That thing rings pretty good when the plastic wears away or falls off.

 

[ckahleer]

Check the can contact surfaces of rocker arms. Verify they are all have a slight convex curve. It my just be the photos, but the left exhaust rocker face looks flat.

 

[Dangitdan]

Thanks guys for all the advice and suggestions. I just got off work and have some more information and pictures to share.

to "Its Being a Long Time", no I haven't checked the oil sump plate yet. It is kind of awkward to take it off at this moment because the engine is sitting on an engine stand thats sitting on a 2 dollar foldable chair right now. I plan to check it when I have everything reassembled.

to "gggGary", Maybe jetting can be an issue. those exhausts are what I got when I bought the bike. I should probably ask the owner if he ever jetted the carbs. It does have air pods, so maybe as a mechanic himself he should have jetted it. The owner use to ride it to races hundreds of miles from PA and it doesn't seem to bother him at all.

to "Bob Wegman", I think I will do that until I have every other possible issue eliminated. those rocker arms are so hard to get off. really doesn't wish to do that right now.

to "jetechmarty" I have it pulled out. the front cam chain guide looks a bit wear off but the back is in really good shape, the rubber is like brand new.

to "ckahleer" I will check on that maybe the day after tomorrow, but I don't recall if they have any flat surfaces.

rocker arms all behave normally, it is free and sits up and down really smoothly.

 

[Dangitdan]

 

[gggGary]

Thanx for the pics. I think we know what your problem is now. Marty for the win!

What does the front cam chain guide look like? That thing rings pretty good when the plastic wears away or falls off.

Wonder what's up with this???

 

[gggGary]

ps you'll find most of the rubber chunks in the sump.
The guides are available and not expensive.
https://www.mikesxs.net/yamaha-xs650-front-cam-chain-guide-oem-256-12231-01.html

 

[Dangitdan]

oh wow i didn't know the front ones use to have rubber on them. now i am happy to know what was making the sound. pretty easy fix.

as for the picture of the cam lobes, what seems like dents are actually just oil reflection. that is all good really.

 

[Dangitdan]

now looking back at the pictures of the piston, the intake side have that clean and lean color to it. should that mean my jet is too small? maybe I should jet it bigger and get it to run a bit richer? the spark plugs, even though I don't have any pictures here, have that good brown color to it.

 

[gggGary]

Piston tops, chambers look fine, using some oil as is expected on a high miles motor.
Valve seals for sure OEM seals are good.
Did you do a compression test before tear down?
Spin the crank so the pistons are down shoot the cylinder walls.
Long as the head is off, check valve faces and valve seats.