cylinder wear question for the gurus

[yozzie]

Hello all, been using this site for a few years now and have used a lot of useful info for my 82 XJ1100.
I recently bought a 78 XS1100 that I have ridden a bit and it uses a lot of oil. I'm talkin a litre every 400 or 500km. Nice trail of smoke out of the left pipe. The PO had owned it for 20 years and said it always had used some oil and it has gotten worse over the last couple years.
I took a compression test and it is 120 across the four. The bike runs well and no knocks, shifts well. Shows about 58,000km.
I pulled the head and jugs off. The top rings are really worn. The gaps are huge, way past spec. Second rings are ok.
Couple weird things I have questions about:

1) the top of piston #2 has a hard black build up on it, like boiled oil. This piston also did not have the oil ring gaps spaced out around the piston. They were almost on top of eachother. I'm thinking with the worn top ring and no oil ring spacing, most of the oil burning was coming from this cylinder. Doesn't appear the jugs were ever off. Never gapped properly from factory?

2) All 4 cylinders have a ridge at the top limit of the ring travel. I've measured the bores twice, come up with 71.5mm. The ridge is LESS than 71.5mm. The ridges are not carbon, they are metal. The ridges are not uniform in depth all the way around.

Any comments? I was thinking of using a ridge reamer to get rid of the ridge and honing, new rings. Thanks for any ideas.

[trbig]

Most of the cylinder wear I've seen happens on the front side of the cylinders. The rods shove the pistons against that wall on the upstroke. They tend to get egg shaped front/back, so make sure that bore measurement is taken there in at least 3 spots down the cylinder.

Unless that new top ring would contact that area you are talking about, I wouldn't mess with it. And speaking of rings, you may have some trouble finding stock rings. What you may have to do is find the next oversize and file/Dremmel them a little at a time to get the gaps right in the cylinders. Be super careful with a cylinder hone and make it a VERY light one to avoid taking any more material away than you have to.


Tod

[yozzie]

Yes, if i remember right the ridge is more pronounced on the front side. I measured the bore all the way down. My manual just gives a measurement of 71.5mm for bore size with a limit of 71.6mm.
I'm wondering why there is a ridge if it still measures 71.5. Is brand new bore spec smaller?

[motoman]

The ridge as you may know is pushed up metal from wear. Ridge-reemer and remove that first(don't wanna break a new ring when started and it WILL if not removed. Mic as trbig stated, then hone and re-mic. Got nothing to loose at this point.

[tadtl1]

spacing of rings

Hi,
Am sure you will space the rings gaps 180 degrees apart too from what you said. That could explain the oil control problem.

[tarzan]

The cylinders are pretty hard from the factory. They probably haven't worn much. The rings probably are worn most. I had that happen on my '78.
I just honed the cylinders and used 1st oversized rings and gapped them properly.Then installed with ring gaps staggered and I have no more oil
usage problems.
IIRC, I used both compression rings and the oil control rings from the new sets, but used the old oil seperators.
Try ebay for the rings.

[trbig]

I would also replace the valve guides while you're that far in. It would suck to do all that to find out that was where the oil usage was coming from.


Tod

[TopCatGr58]

I would also replace the valve guides while you're that far in. It would suck to do all that to find out that was where the oil usage was coming from.

Tod

Hey Tod,

Did you mean Valve SEALS?? Yes, I would suggest the seals, but not necessarily the guides??
T.C.

[yozzie]

It's alive...

Just thought I'd post a follow up for my '78 engine.
I ended up using a ridge reamer and removed the ridge at the top of the cylinders. I was worried about new top rings hammering that ridge, especially with how worn the old top rings were...
Gave the cylinders a light hone, put it all back together and......
it's running great so far, no oil consumption in a few hundred kms!

Did a carb sync and colortune, it sounds good and it's a nice bike to ride! Think I'll keep it for a while!

[Ivan]

Hey Tod,

Did you mean Valve SEALS?? Yes, I would suggest the seals, but not necessarily the guides??
T.C.

Seals wear out from bad guides. When a guide is properly fitted there is only about .001" clearance, and that isn't going to let a lot of oil go through anyway. When they wear, it doesn't take too long for the seals to go south as well. The old chevy V8s didn't have any seals at all, just an o-ring in a groove under the keeper groove that kept the puddle in the top of the cap from dribbling down the stem. Now days they seal everything to prevent HC emissions. When hydrocarbons measure in parts per trillion on modern equipment, even the little bit that normally lubes the stems shows up, so they seal it and use a hardened guide and stem. On the old chevys, they made a retrofit umbrella type seal that actually moved with the stem to deflect oil on a worn out guide, so you could run them another two million miles before the guides need knurled.

Just a little FYI