1974 TX650A Restoration Project

[Jim]

Trying to balance that with the risks/downsides of sticking it out.

If by sticking it out... you mean reusing the old cam, I'd recommend against it. You might get another K or two out of it... hell... maybe even 5-10K... but "riding while nervous" ain't no fun. Add to that, every mile is gonna add to the wear and the fine metal shedding.... it ain't gonna get better. There comes a point where crank and tranny bearing cost's will far outweigh the cost of a new cam.

When opening the top end Saturday there was oil up in the head

Although I'd guess you're oiling OK, that's not a guarantee. The cam chain whirrin' around will sling oil up there... just not enough nor in the right place.

 

[member28833]

^^^^ 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?

Read like song lyrics

 

[member28833]

Add to that, every mile is gonna add to the wear and the fine metal shedding....

Yes, that's why you just open the throttle and ride faster !

 

[member28833]

Oh man, this is all actually good. I would hope that a big bore cylinder conversion could just produce more low end and mid range grunt and maybe even help keep engine temperature down.
Maybe that kind of goal could also improve engine longevity

 

[gggGary]

I'd comment but I'll be accused of stalking.

 

[SomervilleXS650]

@gggGary jump on in!

 

[kopcicle]

I'd comment but I'll be accused of stalking.

stalker

 

[SomervilleXS650]

Although I'd guess you're oiling OK, that's not a guarantee. The cam chain whirrin' around will sling oil up there... just not enough nor in the right place.

Fair point Jim....like I said, while I think I'm getting oil, I'm planning to step through the oil circuit from the pump up to confirm (you know what they say about assumptions and all blah blah )

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

Thanks 2M, really cool to see the nuance.....the thing I've really come to appreciate about valvetrains is how much it reminds me of calculus. To me it's a very tangible example of derivatives and a good way to visualize concepts like instantaneous 'rates of change' in a way that might be easier than the abstract. but I digress....

To be clear....there was some talk in this thread about polishing/sanding/refacing, but none of that was anything I would consider doing. I was going to consider having it 'reground' by a cam shop, but to be perfectly honest I have no idea what the hell that actually entails. I don't really understand how you add material then subtract material and do the required surface hardening/annealing/etc. I wasn't considering trying to DIY the old one.

 

[Jim]

I'd comment but I'll be accused of stalking.

I gotta thick skin... Kinda goes with the hard head.

 

[TwoManyXS1Bs]

... I was going to consider having it 'reground' by a cam shop, but to be perfectly honest I have no idea what the hell that actually entails. I don't really understand how you add material then subtract material and do the required surface hardening/annealing/etc. I wasn't considering trying to DIY the old one.

These oldschool camshafts were forged, with no surface treatments.
A regrind would normally simply grind over the existing lobe, reducing the base circle, to regain the profile and lift...

 

[member28833]

Exactly, no material added. Think If you were to grind the low back side then in effect the lobe is taller.

 

[member28833]

I gotta thick skin... Kinda goes with the hard head.

Exactly, and I'm a redhead Irish, so there is practically no way to get through at all

 

[gggGary]

These oldschool camshafts were forged, with no surface treatments.

If that's the case then you haven't worn through any "hardening" so a clean up of the roughness and run, if the lobe vs base is in or close to spec depending on your need for speed is not out of the realm of possibilities.

 

[SomervilleXS650]

Pulled my rocker box and head apart to check everything out and measure for spec today. Think my rocker arms and rocker IDs are just at the wear limit or just slightly outside. So will probably be looking for rocker arms as well (they also have some visible wearing) but I know those are pretty available. (couple pics here)

It would seem I've tracked down my RH piston carbonization issue...the backside of the RH intake valve was pretty carboned up and even a little wet looking compared to the LH side, so seems that the faulty valve seal was there.

Couple questions for the group...
1) This is a dumb question.....but any general advice for measuring parts with a digital set of verniers? I'll be honest....I never have a whole lot of confidence when I do this. Do you try to use the very ends of the calipers? Anywhere along their length? Do you try to close them with some force? Or lightly? I can generally get pretty consistent readings, but it seems like if I change the variables I just mentioned I can get slightly different readings so just looking for some best practices if ya got 'em.
2) Regarding cam specs (@TwoManyXS1Bs I was looking at cam lobe specs per your earlier post)....any advice for capturing the "A" measurement (overall height from base to top of lobe)? Should I try to draw an imaginary line of bisection through the camshaft and measure across that (i.e. straight up and down)? The lobes are eccentric so doing that way isn't the longest diameter and it's challenging to ensure I am consistently measuring through that imaginary 'bisection plane", if that makes sense.
3) Does anyone have any experience with a WebCam 59a grind? (I believe these emulate the original XS1/XS2?). Would this be considered a "high-lift" cam? I've seen caveats on valve seals and/or keepers about not being for use with "high-lift" cams, but I don't really see this defined anywhere.

Thanks all.

Oh....as an aside....I got my new high performance valve seals (copper/black colored) as well as the Viton ones @5twins recommended (blue). Few pics of both....the "high performance" ones are about 1mm lower profile. In case that's useful for anyone.

 

[Jim]

This is a dumb question.....but any general advice for measuring parts with a digital set of verniers? I'll be honest....I never have a whole lot of confidence when I do this. Do you try to use the very ends of the calipers? Anywhere along their length? Do you try to close them with some force? Or lightly? I can generally get pretty consistent readings, but it seems like if I change the variables I just mentioned I can get slightly different readings so just looking for some best practices if ya got 'em.

Measure something.... doesn't matter what as long as it's hard and repeatable (insert dirty joke here ). Use one of the rocker pins? Put it in the center of the jaws and zero it there. Now measure from the inside and outside edges of the jaws.... note any variation. Won't tell you how exact it is but it will tell you if you can use all parts of the jaws and what allowances are called for.
Google a 1" micrometer standard and see if they're affordable. That'll let you know how accurate your caliper is... at 1" anyway.

Should I try to draw an imaginary line of bisection through the camshaft and measure across that

Just rotate it in the caliper jaws. You'll see when it's at it's greatest dimension.
3) No. Sorry.

 

[Jim]

 

[SomervilleXS650]

Measure something.... doesn't matter what as long as it's hard and repeatable

Embarrassed I didn't think of that. Fairly obvious now that you say it.

Yes, I guess my first question was one of precision. As far as accuracy, a standard is a good call, I don't have one. Seems like I've gotta have something around here I have confidence in to use as a benchmark.

Just rotate it in the caliper jaws. You'll see when it's at it's greatest dimension.

Ok...so you're saying the 'A" dimension is the longest dimension I can measure. Got it.

Thanks Jim!

 

[Jim]

As far as accuracy, a standard is a good call, I don't have one. Seems like I've gotta have something around here I have confidence in to use as a benchmark.

You can use a feeler gauge as a standard for low scale. Won't tell you much about mid or high though...

Embarrassed I didn't think of that. Fairly obvious now that you say it.

Ain't that the way it always goes....

 

[Jim]

Seems like I've gotta have something around here I have confidence in to use as a benchmark.

Piston wrist pin. 20mm +0..... -.005mm
Measure out towards an end where it doesn't usually wear.

 

[Raymond]

This is a dumb question.....but any general advice for measuring parts with a digital set of verniers? I'll be honest....I never have a whole lot of confidence when I do this.

Not a dumb question, I never feel confident measuring things. So thanks for asking and thanks for the pointers, Jim.