Large Spine Frame XS650 / Egli / Rau / Cafe Racer

[rehar]

Looking at the old CAM. Right side, intake valve CLOSED position on the lobe - there is some dark coloration (black). I could rub it carefully and somewhat clean it. Didn't want to get too aggressive on it. And - even black - feels as smooth and slippery as the rest of the cam lobe surface. I imagine it is carbon build up. Anyone else see this? Thoughts on what it is? Does it maybe indicate a slightly leaky valve guide? Loose adjuster? Other? (Also - the engine sat for a few years without use...)

 

[Jim]

That discoloration looks pretty much normal to me. Anywhere there's no "hard contact", they'll be some discoloration from the oil cooking on it.

 

[rehar]

Thanks Jim.

 

[rehar]

Megacycle Cam document says to never re-use lifters (Rocker arm) with a new CAM. I bought some new lifters and putting the top assembly together today and I noticed I have a sticky rocker arm. Put the old rocker arm back in, no problem. Put the new one in, free movement in one position, and sticky to outright binding at the other end of the available motion.

Comparing the old and new rocker, the width of the old one is around 27.89-27.90mm wide. No high spots really. The new one has a high spot, 27.95-27.96.

Anyone else ever experience this? Do I dare massage it with a file - or have it replaced? (I believe it's out of spec.) Haven't measured the other three new rockers but they seem to be free moving in the assembly.

 

[Jim]

Wouldn't hurt anything to dress it down.
I guess it would depend on my mood. Payin' good money for out of spec parts pisses me off to no end.... send it back...
On the other hand, I hate waiting for parts when I have my mind set on assembly. I'd dress it down...
Loads of help... ain't I?

 

[rehar]

Hi Jim, your kind of spot on with my thoughts. I'm on vacation through the 2nd of January and really wanted to get the bulk of this engine back together by then... I've emailed the supplier and hope they have some other suggestions tomorrow. (Like we will overnight a new one to you right away...) Will see what happens.

I haven't rebuilt many engines - very much a newbie. Is it really bad to use the old rockers with a new cam?

 

[Jim]

I haven't rebuilt many engines - very much a newbie. Is it really bad to use the old rockers with a new cam?

As a general rule of thumb, yes. It's best to replace at the same time. As a more practical matter, it depends.
Swapping cams for performance... with a perfectly good cam and usually the rockers will show very little signs of wear. I've reused 'em in such situations.
If you're replacing a wore out or damaged cam, replace the rockers.

 

[Hudriwudri]

@rehar

I highly advice you to also get the hardfaced rockers by megacycle as the material pairing on the sliding surfaces would be perfect.

All the best and lotsa fun with your beautiful build
Christian

 

[rehar]

>>>Does anyone else run a 250-20 cam? And what kind of rockers are used?<<<

The main problem is still the extra material on the side of the rocker - Think I'll file it down. Even with pictures, the supplier doesn't understand.
Anyway - took some lift measurements. I think the stock cam is supposed to me .315" lift. (Maybe the two stock ones I have are worn... but all four are so close...)

View attachment 232758

 

[Hudriwudri]

File the high spot away as, if tolerances between axle and rocker are still good, you will have neglectable lubrication losses if there is a hint more laterali play between head and rocker lateral bearing surface.

Kind regards christian

 

[Jan_P]

When I rebuilt I had wear radially in the rocker arms .Hole
But I kept them.
The side surface with the high spot that is suspected causing the binding ..does not look machined .
Dont believe it is so important But gives the impression of not being quality work.
If it was an important dimension I feel it would have been machined. As would the companies I have worked for
Regularly seen on drawings... google translate -gives " sharp edges are broken " and so

And if the hole bore is to tight and the binding is happening there it is a bigger risk
New parts like Piston pins and so have tighter fit that you can feel Pushing in and out the pin compared to the
old one.
I would check so the binding is not happening inside the hole I would talk to the seller.
About the high spot. If it so they are delivered regularly. Again I feel it not being quality work.
If you don't file it off should it be worn down inside the motor wear metal inside the machine.
Naeee ..eehh don't sound right.

 

[rehar]

@ Hudriwudri, thanks and yes, verified these are hardfaced rockers.
If anyone else experiences this - I'd say - return the item and have replaced with good parts.
Filing the offensive material on the edge of the rocker - much more difficult than I had expected. After spending two days of filing the dimension was finally changed from 27.96mm to 27.89mm (1.1007" to 1.0980"). And it now fits and no sticking.

 

[Jim]

After spending two days of filing the dimension was finally changed from 27.96mm to 27.89mm (1.1007" to 1.0980"). And it now fits and no sticking.

More patience than me. After 10min of filing I'da said screw it and fired up the belt sander.

 

[rehar]

Question regarding CAM positioning, left/right. What is the correct positioning?

I see one youtuber align the cam bearings to a face within the head, and states that the CAMs on the XS650 do float a bit (left / right). A couple of other youtubers don't really address it, but after watching the videos several times it appears to be positioned with "loose tolerance". Checking all the manuals I have for the XS650 only one addresses this. It's has conflicting / unclear information stating the bearings should be positioned as far inward as possible. Even goes so far as to use a threads-all rod to pull the bearings up against the CAM faces during assembly.

If the bearings are up against the CAM, I would assume we could measure left and right positions off the head to the bearing face after positioning - of course - "everything" has a tolerance...

I unfortunately, torqued everything down, then measured it... When will I learn! Considering that everything has tolerance, ahem...

Below, left and right sides were measured in 6 locations each. The rocker cover is tighter than the head.
CAM Position per Rocker cover measurements, rightward Bias: .0018"
CAM Position per Head measurements, rightward Bias: .0025"
Average position rightward bias: .0022"

Is this acceptable?

 

[Jim]

Install the cam covers with the head fasteners just lightly snugged. No gaskets or seals on the covers. Done that way and there's zero clearance all the way across the cam and bearings. The covers will center it. I've got a pic around here somewhere... lemme look for it.

This will answer a few questions.
https://www.xs650.com/threads/xs650-top-end-buildup.52041/

 

[Jan_P]

Well not sure I understand the question.
But generally speaking an axle of the type CAM axle cannot have a fixed position against 2 rigid positions
It have to give expansion possibilities .For thermal and other expansion.
If one bearing is fixed the other cannot be so because the thermal expansion can give forces into the bearing
Which can be designed against But if I recall right the cam has radial bearings. Ball bearings

Secondly what are you using for measuring An electronic caliper can show digits that does not reflect the
accuracy of the measurement. fex xx.xy the y can be off.
I suppose there can be better or worse quality on those

Ordinary 6-inch (150 mm) digital calipers are made of stainless steel, have a rated accuracy of 0.001 in (0.02 mm) and a resolution of 0.0005 in (0.01 mm)

taking this out of memory and not checked it perhaps someone else can chime in
Was it not so that the CAM chain is centered to the right position and then the rest follows on that

Apologize if I have Misunderstood ..

 

[Jim]

 

[rehar]

Thanks Jim, Jan. That's a great picture!

I have unfortunately torqued it down, and it has sat for more than 12 hours.
Question: Can I loosen the bolts and tap lightly on a bearing to adjust?

(Assuming it's needed...)

Other:
Measured multiple times with digital calipers.
My Mule Cam Covers no longer fit with the new CAM in place.
I might find some originals from the donor bike / extra engine...

 

[Jim]

Question: Can I loosen the bolts and tap lightly on a bearing to adjust?

Yes. One at a time, in the same sequence used to tighten... back 'em off to zero and then just lightly snug. Install the cam covers and tighten. That'll ensure the cam is centered. Pull the cam covers back off and retorque the head. Won't hurt a thing.

 

[Jim]

My Mule Cam Covers no longer fit with the new CAM in place.

Try it again after the cam's centered and the gaskets are installed on the covers.
Might even go so far as to make your own gaskets out of thicker paper.