Rebore ?????

[helitrooper]

How can you tell if your engine has had a rebore?
I got a bike with 66K miles on it, recently I burnt out an exhaust valve on the left hand cylinder which I replaced along with the rings & stem seals. When I was in there I noticed that you can still clearly see the honing marks criss crossing the bore, is this normal for an engine that has that amount of miles on it? or, is it a clue that it had recently had some work prior to me getting it?

 

[oblertone]

I'm no expert ...

... but I think what you are looking at is the original finish. I've never heard of an oilhead having a rebore, but I suppose it's possible.

 

[Flipfly]

Quite normal for the honing marks to be there. The bores are nikasil lined, so they don't really wear. Common for it to take 20k+ just to bed the bores in and stop the bke from gulping oil.
The lining makes it very difficult to rebore the barrels, more usual is just to replace them with secondhand ones.

 

[Mzokk]

Friend took an r100rs apart once to replace the valve stem oil seals. 120k and the honing marks were still visible.

 

[The smudger]

I took my 1100 GS engine apart recently, only to repaint it, and found the very same cross hatching, at 115,000 miles!

Nothing to worry about...

 

[(RIP) Miff]

Surely if it had been rebored there would be some marks on the piston crown showing what "oversize" it was.

On my old two strokes, it would have been 0.25 0.50 0.75 etc. These measurements were in millimetres.

Maybe an oilhead would be in thou? Or as it's German, maybe in metric?

 

[cookie]

got 2 sets of airhead cylinders of unknown mileage in a box in my garage. you can see the honing marks in them alright, just not all the way around where they are worn.

you can get them re-nicasiled. ritchie moore does it, or gets it done i guess. about £110 a side IIRC.

 

[skywalker]

I take it your bike has a y piece and non standard can on it which will account for the burnt out valve. The other side will not be far behind.

 

[waterloo700]

Agree with all the comments - my 60k barrels look like new with crosshatch clearly visible.

Interestingly, Jaguar made a pigs ear with Nikasil liners on their 4.0 V8 engines. They were prone to corrosion said to be caused by high sulphur petrol which was about pre 2000. Had to replace loads under warranty.
Never heard of any problems with BMW cylinders.

 

[Fanum]

I take it your bike has a y piece and non standard can on it which will account for the burnt out valve. The other side will not be far behind.

That's the bit to worry about, not whether it's rebored or not