Time for a top end?

crash_davis

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Seeking the advice of the 650XS gurus. I picked up a non-running 1981in rough shape a year ago. Did a lot of work to stop multiple oil leaks, overhaul carbs, adjust cam chain tension, set valve lash, new plugs, timing, fresh oil, new filter and sump, etc and got it running well a few months ago. Sounds great, no unusual noises at idle but riding at higher RPM when letting off the throttle sometimes I can hear a ‘ buzzing or rattling’ sound from the front of the engine. I can’t take a video because it only happens while riding.

My plan was to change oil at 500 miles and inspect the filters but I decided to do it early at 300 miles. I found these metal shavings in the filter (see pictures) and while a magnet wouldn’t pull the shavings out of the filter when I brushed them out onto a rag the magnet was able to pick them up. There was no debris in the sump.

My thought is that this is from the cam chain or guide and tensioner. I did a compression test and got 110 PSI on both cylinders - not great but not knowing the history on the engine I have to believe the engine has never been opened up. If I replace the cam chain/guide/tensioner I should also clean out the carbon, lap valves, new rings, new gaskets and seals. As much as I was hoping to not have to do this (I don‘t have any experience but have watched several youtube videos and read through the excellent guide by Jim on this forum) I believe I have to bite the bullet and tear into the engine? Does my troubleshooting sound correct - the noise I sometimes hear and the shavings in the filter indicative of a cam chain/guide/tensioner wear issue?

TIA for the advice!
 

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Jan_P

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If I should guess it is not
cam chain/guide/tensioner wear issue?

the chain is of " hard steel "
i believe the guide is aluminum with some rubber on it
the tensioner is also hardened and sits at the back of the engine

My first guess is a bearing somewhere ..cam bearing or crank just a guess since I had those give up
But it is a lot there in the filter .. Something is wearing down so a tear down is the way forward I believe
 

crash_davis

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As far as the metal in the screens... was there any there the first time you changed the oil?
Yes, there was. The original oil and filter was in pretty bad condition and there was probably more than that in the old filter. My other thought is that perhaps I need to clean the filter and run it some more and check it - to flush any debris out of the engine?
 

Jim

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Yes, there was. The original oil and filter was in pretty bad condition and there was probably more than that in the old filter. My other thought is that perhaps I need to clean the filter and run it some more and check it - to flush any debris out of the engine?
Well, you have no way of knowing it's history or how often the oil was changed... if ever. That could be metal from years and miles of use. If it were me, I'd clean the filter, put fresh oil in it and go another 100-150 miles and have a look see. What did the sump screen look like?

Re: your noise. I can't even guess without hearing it. Can't really imagine it being the chain guide though. That's usually fairly constant ... not intermittent as you describe.
Also...the chain (and guide) have no way of knowing engine acceleration from deceleration.... at least not enough that it would make much difference. The cam lobes and valve springs will have it loaded up either way.
 

crash_davis

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Well, you have no way of knowing it's history or how often the oil was changed... if ever. That could be metal from years and miles of use. If it were me, I'd clean the filter, put fresh oil in it and go another 100-150 miles and have a look see. What did the sump screen look like?

Re: your noise. I can't even guess without hearing it. Can't really imagine it being the chain guide though. That's usually fairly constant ... not intermittent as you describe.
Also...the chain (and guide) have no way of knowing engine acceleration from deceleration.... at least not enough that it would make much difference. The cam lobes and valve springs will have it loaded up either way.
Thanks Jim, sometimes it's best to 'start simple' and progress from there. I'll clean the filter and change the oil and run it for a while. Costs the least in time and money and years of use/neglect is a very plausible cause. The sump screen looked clean. No debris or chunks of guide as others have reported in this forum. Who knows, it might take a few cycles of oil change/filter cleanings.

In the mean time, I'll continue hunting for what could be causing the intermittent noise as I may have missed something. Wouldn't be the first time something has shaken loose on the bike! It will probably be a couple of weeks until I am able to do the oil change and get the miles on the bike, but I'll be sure to respond back with the results/pictures. Thank you!
 

5twins

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Yes, what you're seeing could very well be past build-up that never got flushed out due to infrequent oil and filter changes. It took probably near a half dozen oil changes and filter cleanings on mine before the filters started coming out relatively clean. Here's my side filter at a recent change. Very few metal chips now, just some little black rubber bits mostly. I attribute them to the rubber ring on the #4 starter gear ......

SideFilter32K.jpg


SideFilter32K-3.jpg


But truth be told, pretty much every one of these can do with a topend job due to their age. The front cam chain guides are routinely failing, shedding their rubber "shoe". Like I said, it's an age thing, you may find very little wear on the metal parts.

I think a front guide that's lost it's rubber might make a rattling sound on deceleration. When running, since the crank rotates in a CCW direction (viewed from the left side), it pulls down on the front run of the cam chain, keeping it taught. When decelerating, there wouldn't be as much downward pull on that front chain run, so it might "rattle" against the front guide if it's rubber strip has fallen off.
 
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