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B1ack_Mi16

What do you guys recon about this wear?

IMAG0135.jpg

 

The vertical lines at top part of each cyl?

 

I'm suspecting I did not file enough gap to the piston rings and that they might be too tight?

 

Had to rip off the head due to one plug thread stripped.. so took it off to get it helicoiled.

 

Plan is to just put it back together, but I think it was a tad much wear as it's probably not driven more than 5000km since new.

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petert

what end gap? what piston/bore clearance? I've got a similar problem even with 0.005" bore clearance.

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B1ack_Mi16
what end gap? what piston/bore clearance? I've got a similar problem even with 0.005" bore clearance.

 

Don't remember exactly the end gap, but I believe it was 0.4mm.

 

Have not got any specs on the piston/bore clearance. Is there any way to measure that exactly while pistons are in the cylinder?

 

When you say 0.005" that's clearance for each inch of bore and equals 0.44mm on my 88mm bores?

 

Maybe I didn't bed it in properly as I did the "hard driving in" style on the rings on this one, full throttle from the beginning, although not too much revs the first hours.

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grandos

Are they scored marks or just polishing to the surface of the bore?

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Miles

Normal for a Iron block, I hate to think what mine is like at 265k

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B1ack_Mi16
Are they scored marks or just polishing to the surface of the bore?

 

Some of them can be felt slightly scored with the fingernail, but most is not.

 

I'm thinking piston rings must have been to large when first fitted.

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petert

0.005" was the overall clearance. ie 88mm + 0.005". I know it was a bit much but once it was gone it was impossible to put back! Anyway, I was surprised when I discovered some nasty marks in the bore. What's the mark I've circled? Can you feel it? 0.4mm is right for the top ring gap. Did you make the bottom ring gap larger?

post-2864-1279102813.jpg

Edited by petert

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B1ack_Mi16
0.005" was the overall clearance. ie 88mm + 0.005". I know it was a bit much but once it was gone it was impossible to put back! Anyway, I was surprised when I discovered some nasty marks in the bore. What's the mark I've circled? Can you feel it? 0.4mm is right for the top ring gap. Did you make the bottom ring gap larger?

 

Aha so that's the bore clearance...

I don't have any measuring equipment to measure the bore accurately enough to come up with a number on that.

 

However I did check out my freshly rebored 87mm T16 block last night and on the bottom of the piston I could not even get a 0.05mm feeler-gauge in between the piston and the cylinder. However at the top of the piston there are probably almost 1mm clearance.

 

I had the bottom ring gap slightly larger on the 88mm engine yes...

I'm not too concerned about that score you've circled in there though, I believe the upper ones are more damaging as that's where there are the most pressure.

 

But I'll do some more investigation on the scoring maybe this evening if I go to the garage again.

 

Any pictures of the block you mentioned?

 

Btw. I did show the marks to my enginebuilder and he agreed with Miles that this is actually quite common wear...

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