Top end wear

Tristan

XS650 Member
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Hi guys.

I’m helping out rebuilding the engine of a friends ‘74 tx650.

Before teardown the bike had various oil leaks, a bodged oil feed pipe to top of engine (see pics) Right hand cylinder running fine, plug looks good. Left side, poor running, popping exhaust, oil coming out of exhaust and oil on plug.

My fears were that bodged pipe had over the years effected top end oil flow and I was correct in my findings.

Cam has pretty bad wear, see lip in pic and rockers have some serious flat spots.

I’ve not had the valves out but I imagine that lack of lubrication has buggered up the valve guides too, hence the oil leak.

I didn’t do a compression test, 1. Because I was pretty sure of the culprit and 2. Half the spark thread on that side is mullered (unloved engine) so I couldn’t anyway with the shorter than plug thread attachment.

Ok so I’ll prob have to find good cam/rockers /valve job.

Next onto the pistons. Bores don’t look too bad, very light scoring that can’t be felt with fingernail and even where the piston hasn’t made contact at the wear line I feel no ridge.

What does concern me is the bottom end of the barrel. Piston walls have blackened and also seemed to have left aluminium deposits to cylinder. This is in the bad side.

Any idea what would cause this? Over heating that side maybe?

My next thought is to hone the cylinders, then check piston wall clearance and then clearance with new standard size rings (if I can borrow them)

Otherwise the bills are gonna go crazy with the re-bored and new pistons too!

Also I noticed that one of the dowel pins was missing on the cylinder to block. Are these just locating or would this effect oil flow too?

Thanks for any advice.
 

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Welcome to the forum, Tristan.

Yup, you'll need cam and rockers for sure.
The oil pump should be checked.
If it's a '74, the cam sprocket should have 36 teeth, but count anyway just to be sure.
We used to use muriatic acid to remove melted aluminum from cylinders, reduces the amount of cleanup honing, avoiding oversizing it.

Avail yourself of all the items in the Tech section.
And, peruse Jim's overhaul thread.

http://www.xs650.com/threads/xs650-top-end-buildup.52041/
 
welcome Tristan,

Only way to tell if the pistons and bore need to changed/bored is to measure them............Looking at the pics and the damage to the Rockers and cam i would say they are kaput...........

Here is a link to make you feel a little better.............new pistons and many have been bought and used with good feedback
https://www.cruzinimage.net/page/3/?s=XS650

Put an add in the classifieds for parts wanted or PM the Baron of Barbaroo member gggGary, he may have some things your looking for. He will probably comment
 
Welcome to the forum, Tristan.

Yup, you'll need cam and rockers for sure.
The oil pump should be checked.
If it's a '74, the cam sprocket should have 36 teeth, but count anyway just to be sure.
We used to use muriatic acid to remove melted aluminum from cylinders, reduces the amount of cleanup honing, avoiding oversizing it.

Avail yourself of all the items in the Tech section.
And, peruse Jim's overhaul thread.

http://www.xs650.com/threads/xs650-top-end-buildup.52041/

Good info there thanks. I’m not sure how easy it is in the uk to get hold of such acid however.

I’ll get onto the oil pump too, along with checking those superbly designed filters.

Thanks
 
cheers guys. the piston materiel came off easily with a light hone. After hone cylinders are still in tolerance for standard rings. I think the bad side overheated and killed the rings. Just received replacements and they are far stiffer, old ones are soft and springy.
 
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