Can you diagnose cam chain guide without disassembly?

[sac02052]

Bike reference - 1981 XS650 H, 19081 miles, purchased in the last month with unknown maintenance history. With normal "new to me" maintenance, the bike now starts and idles fine, carbs thoroughly cleaned, valve clearances adjusted, etc. Cam chain tensioner is flush with +/- 1 mm travel when hand cranking the engine.

When idling it does sound like there is metal-metal contact, so I suspect it has a worn cam chain guide. I have a video of the bike idling, but sound quality is poor and everything sounds tinny on my crappy laptop speakers. There were a few small Al bits in the smaller clutch case filter last oil change, but I didn't see any large black plastic chunks in the sump.

I've searched the forum and read the various threads, but still have three questions ...
1. Is there any way to visually inspect the guide without a major tear down? I've removed cylinder heads before, but I'd rather not have to pull the engine and undo/reset the cam chain timing unless necessary. Looking at the engine images, I suspect the answer is "no, you can't inspect the guide without tear down".

2. Should a guide of that vintage and mileage should be replaced regardless of wear? I suspect the answer is "yes".

3. Is it OK to start and idle the engine for relatively short periods to test other aspects of the engine?

Thanks for listening as I talk through this.

 

[5twins]

1. You are correct in your suspicions - you can't visually inspect the front guide without a tear down.

2. I would have to say yes. I've never found a good one in any of the engines I've torn down (probably 8 to 10). I think age is the big factor, mileage not so much. The rubber strip on the guide usually isn't badly worn, it's falling off. The glue used to bond it to the aluminum base is failing now, probably due to age.

3. You should be OK running the engine.

The symptoms of my guide going bad were a ticking at start-up for 20 seconds or so. When I tore it down, I found the rubber strip on my guide about 2/3 of the way unglued .....

I figure the loose rubber slapping against the aluminum base was responsible for the noise. Once oil started splashing around, it quieted it down. What you'll want to do is inspect the old oil you drain for metal flakes. This would indicate the rubber strip has fallen completely off and the chain is running against the aluminum base, grinding into it .....

If you find this, I'd say you need to change the guide now. If not, you could probably run a season or two, but planning on the change in the future. At near 20K, I'd change the chain too.

 

[sac02052]

thanks.

I'm not getting any ticking, just a steady "dryish" sound that seems to be the timing chain. The top end is getting oil, so the pump seems to be working correctly.

i don't recall seeing any ground aluminum in the last oil change, but i wasn't looking for it either. I haven't disposed of the oil yet, so i could pour it out and double check

Sounds like I'll take the engine out for a closer look. Seems to be a recurring theme among my current/future projects.

 

[xjwmx]

My experience is the sound isn't very noticeable with the rubber missing, so your metal on metal sound might be something else. First thing I would check visually would be the crank ends. The crank can separate and one or both ends will noticeably wobble while turning with the starter, and makes a very noticeable wirrrr-ing sound while idling. The crank coming apart is sometimes associated with a big clunk sound when the starter somehow catches wrong and presumably breaks the crank...

 

[peanut]

I wouldn't start removing the engine just yet until you have investigated some possible alternatives .
There is a lot of things that could be causing the noise .

During rebuild my crankcase showed signs that the back of the clutch basket had been rubbing on the crankcase. I checked clearances carefully during rebuild and there didn't seem to be any issues but a few hundred miles later I started to notice a distinctive whirring rubbing noise in sync with the engine revs .
I now suspect that the additional clutch washer that was left over after my engine rebuild was fitted previously to space the clutch basket off of the crakcase .

Use a stethoscope or a long shafted screwdriver held to your ear to see if you can pinpoint the source of the noise .
Its not a major job to remove your covers to check everything and you can run your engine at idle with the covers off for 15-20 seconds or so without causing any harm if you cannot spot anything obvious with the engine off.

You can see the clutch wear on the crankcase in the first few seconds of my video.

 

[Superjet]

The majority of the aluminum and plastic parts were in my screen filter and not the sump. I found the guide after taking the head off misaligned causing the wear shown. Not pretty. Cam chain had nearly no threads left after adjustment.

 

[sac02052]

Good points all, thanks for your input. Now my wife will get to laugh at me as a stick a screwdriver handle in my ear.

For @xjwmx, I'm confused how a crankshaft would split at the end. Any chance you have a pic to show it better?

The left side seemed fine when I was manually cranking it during the valve adjustment, but I wasn't focused on the crank. I didn't look at the right side since the clutch cover was still on.

 

[xjwmx]

For @xjwmx, I'm confused how a crankshaft would split at the end. Any chance you have a pic to show it better?

I don't know the fine details of the assembly, but the crank is made of several sections that are pressed together end to end. If you look at a picture of it you,d see there's no other way the piston rods, for example, could be put on the crank except for them to be put on between sections. Some people will weld the sections together once the crank is assembled, as extra insurance against them separating. When they separate, one or both ends will wobble. When my bottom case cover was off and nothing was holding the crank, one end would just bob up and down. With the case together, the case keeps it from doing that, so it becomes the end wobbling. It might be too fast to see if running, but turning it with the starter you can see it.

 

[sac02052]

Ahhh, now I understand. Thanks for the add'l info.

 

[xjwmx]

Like Peanut was saying, check everything except the guide first (incl. separating crank), because once the engine is out it becomes harder or impossible to do that and you don't want to take the engine out and put it in twice.

 

[sac02052]

Good point xjwmx. Conveniently, we're traveling this weekend, so I didn't rush out to the garage and pull the engine before the thread evolved.

Sounds like the order should be:
1. Diagnose using screwdriver
2. If 1 doesn't ID the issue, take off the side covers and check for smooth crank rotations, clutch scraping, or other signs of noise
2a. Maybe replace 15w-40 oil with 20w-50 to see if that dampens the sound.
3. If none of that works, pull engine and inspect cam chain guide.
4. Buy a gasket kit because this process is sure to destroy some 37 year old gaskets, and the tappet cover o-rings are damaged anyway.

 

[sac02052]

Update#1
The old oil from the first oil change after purchase had some glittering metal flakes but not as bad as the pics from 5twins. I have no idea how long it had been since the last oil change, so could have been regular engine wear. No big plastic chunks.

Screwdriver stethoscope test did not detect anything weird after checking multiple spots (both cases, both cyl heads, cylinder bases, etc.). When put on the cam chain guide area in front of the cyls it was slightly higher pitched that in other spots, but no defined grinding. All other spots sounded the same, no grinding, clunks, or excessive noise.

Crankshaft end on left did not wobble when running, but i didn't check the right side since taking the clutch cover off required moving the pipe to reach the allen bolts. And I was short on time.

I put in some 20w50, so we'll see if the dryish sound gets any worse over time ... or if it was all in my paranoid head.

Thx again. Now on to fix the rear spokes, front light, and swingarm bushings.

 

[xjwmx]

This might be a way to diagnose cam chain guide without disassembly. Post # 26
http://www.xs650.com/threads/cam-chain-adjustment-new-better-method.17837/page-2#post-551768

 

[sac02052]

@xjwmx Thanks for the link, i'll give that a try as well. One more question regarding the possible splitting of the crank shaft.

As mentioned before, I haven't yet pulled off the clutch cover but before I do (and drain the oil yet again), is it *likely* that the RH end of the crankshaft is OK because:
- the LH end of the crank shaft seemed OK. Any "wobble" was most likely caused the entire engine wobbling due to general vibration.
- the screwdriver stethoscope did not detect anything weird when held against the clutch cover and nearby engine cases.

I imagine/assume that if one part of the crankshaft were loose then the whole thing would vibrate, but that's just a guess.

 

[xjwmx]

In my case the left end looked fine but the right end was wobbling like a top. Sound travels around the motor so much that listening for location has never worked for me. If you clean the pan good first you could re-use the oil.

 

[sac02052]

Update #2 - The garage gods smiled on me today.
Right engine/clutch cover came off without tearing the gasket. Everything was nice and shiny inside, the various gear teeth looked good

there were no plastic shards, the right side of the crankshaft spun cleanly (no discernible wobble, i had already checked the left side) with both starter-only and for a short period at engine idle. The clutch basket was not rubbing against anything.

Re-assembly was a little tricky to get the oil pump/tach drive gears to mesh with the gears on the crankshaft, but everything worked out and the kickstarter seems to still be engaged.

Ran it for a short time with a tappet cover off and the oil pump is definitely feeding the cam shafts, valves, etc. Then ran it at idle with the cam chain tensioner cover off and the plunger just buzzed a little. No major jumps.

So the original noise is still present but it may just be normal for this bike ... or all in my head.

I'll move on to other aspects of this project and just keep an eye on the noise once I start actually riding it.