clumsy boy

dunk 1 · Post by **dunk 1** » 15 Mar 2009 14:32

due to a slightly strange noise - one of those barely on the edge of hearing i decided to inspect inside the rear cylinder- i had lots of fun removing it from the frame and all looks fine - the problem is as i did this in managed to knock a very fine shaving fromn the top edge of the piston on the low bit between the two raised areas. does this mean i have to now buy a new one - it is slightly sharp there now? yours embarressedly - duncan

Steve Brown · Post by **Steve Brown** » 15 Mar 2009 21:09

You should be able to dress it with a file, I think. Get rid of sharp edges and smooth out any sharp bottoms of grooves etc. If it was left sharp in any indent it 'could' just, almost, possibly start a crack.
In practice though you'll see many pistons damaged by other traumas that have run for many thousands of miles. In the area I think you mean, there is a lot of metal, so room for a good margin. If it is only sliver I wouldn't panic, just smooth it gently.
If you're a worrier, I could sell you a piston!

dunk 1 · Post by **dunk 1** » 16 Mar 2009 07:26

Yes I am worrier but i counterbalance this with being fat too tight to part with cash unless i have to (yorkshire roots)- but thanks for the offer anyway. I took the burr off with fine wet and dry and it went back together fine- once you've done something once its always so much easier. What had worried me was that the nick was on the crown top edge and that this could in some way affect combustion or the bore but we'll soon see. - thanks - Duncan

Steve Brown · Post by **Steve Brown** » 16 Mar 2009 23:29

Dunk, it won't affect the combustion so long as you smooth everything and of course, don't take too much away.

TIP! for anyone dressing pistons for whatever reason- Try to avoid using emery cloth/wet'n dry. Use a scraper or clean file instead. It can, just possibly, maybe even, happen that you leave behind small amounts of the grit in the soft alloy. It is of course designed to be abrasive so not best practice.
Mind you, I got away with it plenty of times. Then I started to work on TZ's and TR Yamahas. Piston dressing was a regular thing and I learnt about this tip then.

Sorry, am not trying to make you paranoid-honest!