Rocker Arm Shaft

[Paul Sutton]

This week I have been working on an engine with only 2064 genuine miles on it. Unfortunately the valve faces have deteriorated over the last 32 years in storage so I need to re-lap the valves and replace the valve stem seals. The shafts were very very tight and a slide hammer would not touch them. I was able to withdraw them sufficiently to allow the rocker arms and valves to be removed by extracting them with a length of threaded stud fitted with a nut/washer and a long reach socket. My big question now is how do I safely press the shafts back into position now that the valve work is complete? Remember the shafts have not been fully removed so are already aligned awaiting that final magic touch.

Thank you for any advice - Much Appreciated.

 

[5twins]

I can't really think of any other way other than to gently tap them back in. I would put a bolt in the threaded hole in the end of the shaft and tap on that.

 

[Jim]

Tap 'em back in with a brass drift and a hammer.

 

[Paul Sutton]

Excellent - Thanks for the advice 5twins and JimD54. I have some spare brass so will make a drift and compare it to using a bolt. Will be this week's science project.

 

[TwoManyXS1Bs]

Paul, have a look at:

Post #826, Mailman referencing chips during shaft removal.
http://www.xs650.com/threads/mailman’s-xs2-a-full-on-restoration.51520/page-42#post-554372

Posts #849-#852.
http://www.xs650.com/threads/mailman’s-xs2-a-full-on-restoration.51520/page-43#post-554516

Myself, I'd want to completely extract the rocker shafts, clean out any/all debris and chips...

 

[Paul Sutton]

Thankyou TM for the references. I was sent the wrong valve stem seals so have time tomorrow to completely remove the shafts and check for bits and pieces. I shall report my findings.

 

[kshansen]

Not sure if this would work but considering the different rate of expansion between steel and aluminum I would be tempted to pop the head in the oven at say 250ºF and let it sit for maybe 15-20 minutes and then see if they come out easy. Same for reassembly and with cold pins in warm head they should move even easier! Never liked press fitting anything into aluminum. If I had a head off an engine I'd try it in morning!

When I was working on big diesel engines it was common to have to heat pistons to get wrist pins out. Sometimes would just have a bucket of hot water and let them soak a bit and the pins would slide out easy. When assembling new pistons to the rods just put one snap ring in piston and pop in shop oven for a few minutes and pins slid in easy.

 

[Paul Sutton]

Update, removed the shafts completely but found no bits of metal. Have tested tapping the shafts back in with a bolt screwed in and it will work but a bit tight, but I think I will try this with the head warmed up as per Kshansen's comments. In a TM reference above there is a comment about the shafts sliding in easily - Is this an XS specific comment or general engine building good practice?

I did find another issue in the daylight. One of the cam lobes has some scoring to it. Must have run out of oil at some point. Is this something I can address at home, or do I just leave it, or get it reground professionally?

 

[Paul Sutton]

Just took some closeups:



The lobe is rough to the touch, perhaps I could gently grind off the high spots with a fine hand stone?

 

[TwoManyXS1Bs]

Paul, in the dealership, the rocker, and the cam, would be replaced.

The rocker pad has to have a 30mm radius, with a specific arc center.

Post #3.
http://www.xs650.com/threads/yamaha-xs650-valve-train-geometry.40042/#post-400799

And, the camshaft has measurable go/nogo limits.

Post #2.
http://www.xs650.com/threads/yamaha-xs650-valve-train-geometry.40042/#post-400798

Sure, you could stone and polish the blemishes, and it'll run.
Don't know anything about any hardfacing on those.
This is the "gray area".
Not my recommendation...

 

[TwoManyXS1Bs]

...there is a comment about the shafts sliding in easily - Is this an XS specific comment or general engine building good practice?

It's XS specific.
You may simply be at the beginning of hole swaging. Look closely in there, and see if you can see annular aluminum disruption where the end of the shaft resides.

Myself, I'd slide the shafts all the way in, minus the rockers, and check for up/down slop...

 

[gggGary]

Looks like one of those times you wish there was a parts engine in the shed.

 

[Paul Sutton]

Thank you for all the extra information TM. I will now consider my next move. May be best to get the lobe regrind if this is possible. Will also start an Ebay search for another camshaft, but this will probably take some time to throw up a result.

Thank you - Off to the garage to play.....

 

[Paul Sutton]

No prizes for guessing what I picked up today.....A replacement camshaft! This will go into temporary storage while I attempt to dress that damaged camshaft and see how it copes for a couple of hundred miles.

 

[Jim]

I'm curious as to why you're not using the newly acquired one?

 

[Paul Sutton]

JimD54, Because I need to get a rocker arm also. The other was scored by the camshaft so I figure while I wait for one I can have bit of a play. All part of learning.

 

[Jim]

Gotcha...

 

[Paul Sutton]

Thread concluded because I got a NOS rocker arm the day after the camshaft so installed both. The rocker shafts tapped back in nicely using a bolt screwed in but it took a lot of tender loving care (i.e. gentle wriggling) to get the rocker arm to align with the shaft.

Thank you for all advice given Guys.