Cleaning pistons ... How to ??

[The Buddha]

OK How to clean pistons .... I had water in this motor from a hole in the head ... and the thing is getting new rings and has been honed and new wrist pins and circlips ... How do I clean the pistons ... they look fine ...
Also fitting new rings and pins in it ... do I need to put the pistons back in the same bore they came from ...
The motor also has surface rust on the connecting rods very very little ... where else ... no idea I just see the rods ... Is that bad ... How bad ...
Cool.
Srinath.

[Dom]

Do they have carbon on them?  If so I have heard of using oven cleaner and fine steel wool.

[Dom]

Have to be careful, though.  What are the pistons?  Aluminium?  Some cleaners can be caustic to aluminium...they'll cause pitting.  Zep-alum is an aluminium cleaning product that works wonders.  Also you can use muriatic acid or boric acid...one of the acids for cleaning aluminium....it's the main ingredient in Zep-Alum.

[dgyver]

If these are stock pistons and since you honed the cylinders then it really won't matter which one goes where. It is not going to hurt to put them back in the same hole. If they are oversized and the cylinders were bored for each piston then I would make sure they went back into the same hole.

I have used a very fine 0000 steal wool to clean pistons before. Aluminum wheel polish works well too. As for the rods, use the same steel wool and look for any pitting.

[Dom]

I bought a number and letter stamp set at Harbor Freight  and usually the first thing I do when I pull apart the engine is stamp on the top of the pistons which numbers they are and use a "V" to point toward the front of the vehicle.

[The Buddha]

I got most of the carbon off with a gas soak ... now the new question ...
I have heard I am supposed to lightly rough the sides of the piston with 1000 grit sand paper similar to the hone in the cylinder ... is that right ...
Cool.
Srinath.

[dgyver]

now the new question ...
I have heard I am supposed to lightly rough the sides of the piston with 1000 grit sand paper similar to the hone in the cylinder ... is that right ...
Cool.
Srinath.

I have never heard of that before.

[JeffD]

Well When I rebuilt a VW motor.  The pistons were siezed in the cylinders and had rusted.  I got them out.  hit them with a wire brush, new rings, honed the cylinders, prelubed and cranked it up. and ran fine until I moved and left the bug in arizona.  

It also had rust on the connecting rods, and I got it off with the same wire brush, no problem.

[Dom]

now the new question ...
I have heard I am supposed to lightly rough the sides of the piston with 1000 grit sand paper similar to the hone in the cylinder ... is that right ...
Cool.
Srinath.

I have never heard of that before.

The pistons shoud never directly contact the cylinder walls.  The reason you hone the cylinders is so the rings seat properly.

[The Buddha]

OK That sounds good. The sides of the pistons ... what did you do to that ... in anycase doesn't matter much I suppose, it should never touch the cylinder, always rings should be in contact. I got the pistons clean, I have rust in the cylinder whihc I honed out but still looks like sheite ... If I get the bike off and running and I like it I might over bore it to 972. I already have the stock size parts whihc I bought before realising how screwed up the cylinder was ... anyway ...
Cool.
Srinath.

[GRU]

clean it like this  :mrgreen:
http://www.srtforums.com/forums/showthread.php?t=115125&page=1&pp=15
bwahaahha

[cernunos]

Srinath, the reason to "buff" the skirts of the pistons is to put back a facsimile of the original grooving when the pistons were new. The grooving actually creates small pockets for oil to adhere to so that the pistons don't have to touch the cylinder walls. Pistons do touch the walls except for a small film of oil once everything gets to moving around and oil gets to splashing around. I would put the pistons back in the original cylinders unless you had so much wear that it didn't matter anyway. Also ensure, of course, that the ring lands are clean and the rings have some back-spacing in the lands. Lovin' the Baby GS and everyone on this forum.

C.......

[Kerry]

 C!  Welcome back!  

[The Buddha]

Hey cer ... how you been ... PM or post on here man we missed you ...
Cool.
Srinath.

[Jughead]

Hey I just found this Thread.How to clean Pistons.OK if they are covered in Carbon either Berrymans or Vinegar.If you clean them in Vinegar take the Rings off.
One reason for Scuffing the Pistons in a Two stroke is to Get rid of any High spots that are rubbing the Bore.I usually clean them up a little with 400 Grit wet and Dry Paper. It also helps retain a little oil while the Rings seat.

[OctaneMotorsports]

The pistons shoud never directly contact the cylinder walls.  The reason you hone the cylinders is so the rings seat properly.

No offence, but are you kidding me?

[natedawg120]

The pistons shoud never directly contact the cylinder walls.  The reason you hone the cylinders is so the rings seat properly.

No offence, but are you kidding me?

no he's not that is right.  That is the entire purpose of the piston rings.  There would be to much friction if the entire piston made contact with the wall of the cylinder.  thus the rings create a seal with the piston and the cylinder wall.  Otherwise engines would be really sensative to hot and cold and if any one part warmed or cooled way faster than the other. 

[MarkusN]

The pistons shoud never directly contact the cylinder walls. The reason you hone the cylinders is so the rings seat properly.

No offence, but are you kidding me?

no he's not that is right. That is the entire purpose of the piston rings. There would be to much friction if the entire piston made contact with the wall of the cylinder. thus the rings create a seal with the piston and the cylinder wall. Otherwise engines would be really sensative to hot and cold and if any one part warmed or cooled way faster than the other.

Everybody notice how old that original post is.

Anyway, on the topic: Both parties are right to an extent. Of course it's the rings that do the sealing and have to break in on the cylinder walls. But that doesn't mean that the piston does not contact the cylinder wall anywhere. Of course it does, for guidance (not sealing) purposes.

[The Buddha]

The piston does contact the cylinder wall especially as the ring land wears. that is commonly referred to as piston slap. BTW the auto engine shop that did the ring refit on mine used their standard wire wheel followed by their parts washer type thing. I entirely forgot about that and never updated this post. Till cafeboy's eliminator showed up I had forgotten how much I missed the 900 and 1000 I have, and a renewed interest to get those 2 back on the road.
I wonder how that 900 is going to work, I had rust and so much crap. I guess I put it back together and I'll know. Its been over a year since I honed the cyls and fitted pistons and rings. Time to get back to work I guess.
Cool.
Srinath.

[OctaneMotorsports]

I apologize, I thought you said "the piston never touches the cylinder wall". But, although it is not really supposed to, it will 99% of the time even in a perfectly set up engine.