1974 TX650A Restoration Project

[member28833]

Regarding the seen camshaft galling and rocker arm surface condition, expected standards to me is unclear as to what wear condition is acceptable and for what intended use of the engine.
Being a guy who has always played with a limited budget for motorcycles, I'm seeing a lot of temptation to continue using the shown camshaft and rockers. Agree that those items do show wear but what used engine does not? I've had fun rebuilding a few motorcycle engines when younger and didn't know better to evaluate similar seen wear as "bad". Now, older and wiser (lol). It still would tempt me to polish those cam lobes and rockers on a polishing wheel to see if surface improvement could be made?
But then there is the consideration of protecting the investment in the 750 Big Bore mod which my just deserve being more particular and opening the wallet again.
More example pics and opinions on acceptable wear condition? I find this is interesting and why we are here..
-R

 

[Jim]

Regarding the seen camshaft galling and rocker arm surface condition, expected standards to me is unclear as to what wear condition is acceptable and for what intended use of the engine.
Being a guy who has always played with a limited budget for motorcycles, I'm seeing a lot of temptation to continue using the shown camshaft and rockers. Agree that those items do show wear but what used engine does not? I've had fun rebuilding a few motorcycle engines when younger and didn't know better to evaluate similar seen wear as "bad". Now, older and wiser (lol). It still would tempt me to polish those cam lobes and rockers on a polishing wheel to see if surface improvement could be made?
But then there is the consideration of protecting the investment in the 750 Big Bore mod which my just deserve being more particular and opening the wallet again.
More example pics and opinions on acceptable wear condition? I find this is interesting and why we are here..
-R

Pretty simple really.

 

[gggGary]

OK @Jim are the regrinders hardening their work?
Something I've wondered.
A quick look about sez no.....
https://highwayandheavyparts.com/n-12799-the-camshaft-reconditioning-process.html

@kopcicle want to weigh in?
I know nothing here but... LOL
Apocalypse coming, gotta make it run.
If you don't have a feel for this type of thing odds of making it worse are real good.
I'd be thinking jig up the cam so it rotates very slowly, work with a water stone across the whole width of the face, lots of mineral spirits against the profile and smooth down the galling, follow up with polishing. ditto the follower faces.
Or find a good used cam, rockers

 

[gggGary]

ps lay that old cylinder down use some white paper as a background, shoot more pics lol
piston sides too.
what oil were you running?
any chance you had gas in the crankcase?
Lets see inside the small end bores too.

 

[RustiePyles]

OK @Jim are the regrinders hardening their work?
Something I've wondered.
A quick look about sez no.....
https://highwayandheavyparts.com/n-12799-the-camshaft-reconditioning-process.html
View attachment 187210
@kopcicle want to weigh in?
I know nothing here but... LOL
Apocalypse coming, gotta make it run.
If you don't have a feel for this type of thing odds of making it worse are real good.
I'd be thinking jig up the cam so it rotates very slowly, work with a water stone across the whole width of the face, lots of mineral spirits against the profile and smooth down the galling, follow up with polishing. ditto the follower faces.
Or find a good used cam, rockers

Typically reprofiled cams are not "re-hardened" per se. But rather they are welded up with hard-facing rod and ground back to size. Cold grinding should not have any negative effects on the applied hard facing. That is how it's supposed to be done, I cannot vouch for the folks re-profiling XS cams though. This was the method Potovin used and most of the folks after them did it as well.

 

[Jim]

Apocalypse coming, gotta make it run.

Yeah, zombie apocalypse and I'd run that cam 'till it cooked itself and wouldn't run anymore. Other than that......

Typically reprofiled cams are not "re-hardened" per se. But rather they are welded up with hard-facing rod and ground back to size.

I'm not well versed on cam grinding. That's the only method I'm familiar with too. I knew of a local place when I was a kid that put 'em (automotive....aviation ) in a nitriding oven. Not sure if that's done any more?

 

[member28833]

Just for more perspective today on an example of the 82 camshaft which clearly suffered one exhaust lobe catastrophe, I looked very closely at the 3 other lobes. Looking for by "the book" metal flake off or becoming pitted.
It was fun to really look into what deformities were present as that engine was running. If the one exhaust lobe did not suffer the catastrophe, would the other lobes have lasted much longer?

I believe there are many XS650's running with cam shafts in a similar condition.
Remembering the better looking camshafts of my XJ650 and FJ1200 which of course were four cylinder utilizing Shim and Bucket valve trains. Perhaps a much better design for higher rpm, horsepower, and longevity.

 

[Mailman]

I really like the look of that kit, that was an interesting side by side comparison. I find it interesting how much additional finning they’ve added to that cylinder, I sure wouldn’t mind the additional cooling here in hot Arizona!
It’s also interesting that the gasket surface area is absolutely flat and doesn’t have that serpentine groove cut into it like the factory jugs, what does that groove do anyways? One more observation, I like how cleanly the cylinder liners transition to the barrels. On my factory liners there is a clear line that can be felt with your fingernail.

I also wanted to add my thoughts on oil supply to the cam and followers. When I rebuilt my XS2 motor the first time I pulled the rocker shafts and was surprised at the amount of crud that had built up in that space.

Here’s a photo looking into the space that I just pulled that shaft out of.

I also found bits of silicone gasket material that wound up stuck in that area as well as metal shavings.
Given that the oil that flows through this area supplies the feed to your camshaft lobes, it would be easy to see how one or more of the small passageways could get blocked or obstructed.

 

[Mailman]

Just for more perspective today on an example of the 82 camshaft which clearly suffered one exhaust lobe catastrophe, I looked very closely at the 3 other lobes. Looking for by "the book" metal flake off or becoming pitted.
It was fun to really look into what deformities were present as that engine was running. If the one exhaust lobe did not suffer the catastrophe, would the other lobes have lasted much longer?
View attachment 187229
I believe there are many XS650's running with cam shafts in a similar condition.
Remembering the better looking camshafts of my XJ650 and FJ1200 which of course were four cylinder utilizing Shim and Bucket valve trains. Perhaps a much better design for higher rpm, horsepower, and longevity.

Interesting, man it would be fun to have access to your shop equipment!

 

[GLJ]

I sure wouldn’t mind the additional cooling here in hot Arizona!

A few more horsepower wouldn't hurt either.

 

[kopcicle]

I have an additional view of such camshaft damage. That hard metal gets all through the engine. A complete and exhaustive cleaning is necessary.
The oil pump is marginal and all the oil passages are suspect. That hard metal is now hidden in all the bearings and bushings. Anything you do now is compromised by the previous damage.

 

[member28833]

That hard metal gets all through the engine. A complete and exhaustive cleaning is necessary.
The oil pump is marginal and all the oil passages are suspect. That hard metal is now hidden in all the bearings and bushings.

For sure! And all the accumulated other hard metal particles from the transmission, crank, just all of it, getting only strained and pumped to the top of the engine, sprayed into the hot valve train to be mashed by the camshaft.
Frightening if you think about it.

 

[Jim]

As the cam and followers shed metal, it'd wash down into the sump. Bein' as how we have wire mesh screens instead of filters, getting pumped back through the engine is a concern. The one saving grace we have is the sump magnets... both on the sump screen and drain plugs. Since the cam and followers are ferrous, a good bit of that metal is trapped on the magnets. Can we have a look at the sump screen and drain plug magnets?

 

[gggGary]

It'll migrate to the tranny and build up the gear teeth.
Had a cb900f I abused heavily. The cam lobes on the far rh cylinder were largely worn down didn't bother anything for many thousands of additional miles.

 

[hovel]

Are we building a case for non-unit construction or at least semi-unit construction ? Given a choice, I sure wouldn't be running the same lube in my trans as in my crankcase.
Of all the "unit" engines I can think of, the Morris Mini bothered me the most.

 

[SomervilleXS650]

Hey all. Busy couple of days. Brought the head and rockers home this week for inspection (bike is an hour away right now....can't take your "cylinder porn" pics at the moment @gggGary ). I'm planning to give the head a once-over this weekend and replace the valve seals. I picked up a set of "high performance" ones (ha) and a set of the viton ones that 5twins recommended as well. Will check them out and report back.

I'm still unsure about how I want to proceed with the cam and rockers. Been looking around at options....concerned about a performance cam opening the rabbit hole of performance springs, valves, seat-work etc. Trying to balance that with the risks/downsides of sticking it out. I think it depends on the options I find. (to that point - I'd be curious to hear from anyone who has installed a Hoos Shell#1 or WebCam 59a and has feedback.)

Few things to respond to the posts above.... I wouldn't assume everyone here has read this whole thread but just to orient everyone to the history a little:
- Bike/motor had ~20k miles when I got it. Don't know a lot about the history, bought it from a local guy who scouts bikes and flips them. I know it had been sitting for quite some time (+10 years) when he got it. He got it started pretty easily but again, was just buying/selling
- I rode it 3 or 4 times before putting it to sleep for the winter and deciding to do a full resto on it. Couple hundred miles probably
- I pulled this motor last year, completely opened it up (cases), vapor blasted the cases myself, and reassembled. That included washing the crank and bearings with fresh mineral spirits and checking the crank tolerances per the service manual. The bearings all seemed OK.
- When I rebuilt the motor I found a crack in the rotor of the oil pump (here). Not sure how long it was there.....could have been from when it was woken up from hibernation.
- Since my rebuild I've changed the oil several times, several times in the first 200 miles, and sub-1000 mile intervals since
- I’ve always used Valvoline 20W-50 oil (blue bottle, the one marked for bikes/wet clutches)
- Since pulling the motor Saturday I've not yet pulled the sump (will report if I find anything of note in there)
- When opening the top end Saturday there was oil up in the head
- @Jim Here are some pics I took of the rocker shafts when I had it apart last year for my rebuild. There is definitely some scoring on at least one (first pic). The other pics are after vapor blasting.

What does this all mean? To me, I think it's likely that if there was an oil starvation issue (which I agree, seems completely likely, especially w/ a cracked oil pump) I feel fairly confident that I have flushed any of the 'active' remnants (shed particulates, etc) and that I fixed the underlying issue. So I would say the issue I am wrestling with is not fixing the underlying problem (I believe I did that last year) but rather dealing with any remaining fallout from the original issue. Of course, I am double checking my feed tube, top end, passages, etc are all free and clear now that it's open, but that's the hypothesis I'm working from here.

Thanks to everyone for the great points to consider (appreciate @Machine's very cool scope pics and asking some of the same questions I'm asking myself). Additional feedback is of course welcome.

 

[member28833]

Awesome pics Somerville, cheering for your success!

 

[Mailman]

What he said!

 

[TwoManyXS1Bs]

There's bikes in here with guts in much worse shape.
Yet, somehow seem to run.

Another black/white, go/nogo threshold for your camshaft is the actual measuring of its cam lobes. Check yours against this manual excerpt, Height "A", Width "B", and the limits.

I'm pretty sure that at least 90% of the vintage bikes in here, and out there, would fail this.

Concerning sanding/polishing the cam. If you are really picky about lobe profiles, consider the imperceptible entry ramps. These graphs shows the micro-magic that occurs there.

Gets pretty complicated, doesn't it?

 

[kopcicle]

^^^^ not really.

You can only lift a valve so early without crashing into the piston.
You can only lift a valve so quick without breaking stuff.
You can only hold it open so long before you run out of time to close it.
You can only use so much spring pressure before you break into the oil film at the rocker/cam interface.
You can only introduce just so much overlap before you bleed off pumping-efficiency @ (at) RPM)
Intake resonance before exhaust resonance or exhaust resonance before intake resonance?
The all important rod length to stroke ratio vs cam lift to rocker ratio.

In the end what are you trying to accomplish at what RPM?

TANSTAAFL

What's so hard about that ?