Pulled my top end planning on just replacing my rings.  My piston dosn't look so good so it gonna get a new one.  I was wondering if anyone has any ideas what would cause the shiny line in the piston just below the top ring on the exahust side.  The ring groove is considerably wider there.  It seems the ring land below the top ring on the exhasut side in deformed down and has pushed out and has been rubbing on the cylinder.  The top of the piston looked normal before i cleaned it.  The cylinder looks perfect.  The bike has about 4 rear tires on it and i think this piston is the original.  The bike has a gnarly pipe rad valve and a JD kit in the mikuni.  I run 50/50 110 race gas / pump premium, Lucas oil 40:1.  I am the third owner and it was in good shape but little things led me to believe the original owners were not rock star mechanics.

Is this normal wear, or should i be looking for for a issue that will shorten the life of my new piston





Thanks for any comments

not too sure. thats kinda random there on the piston.. i wouldnt worry about it though. make sure your cylinder is in good condition and still in spec. and replace your piston/rings

just change the whole piston kit and check yoiur crank for play.

and thats a wiseco piston................

Looks fine too me but that wear does look unusual, although if it was me and had it apart ild change it for peace of mind.

Edited by noysy1, 15 April 2012 - 04:17 AM.

Thanks for the comments.  I guess the guy i bought it from was right when he said it had had the top end done a while back.  I ordered a new stock pistion, i will put that puppy in and roost away for another year.

Any pics of the cylinder?  I'd look closely at the exhaust bridge for wear.  May consider more oil and a longer warm up cycle if there is wear.

If that is a wiseco the exhaust side piston wall should have been drilled to help lubricate the exhaust bridge.  I did a rebuild of my sled this year after I bought and noticed that the upper ring land was significantly wider on the exhaust side.  I believe the cause may have been detonation although the crown did not show excessive signs of it.  It is hard to say how the PO operated the sled before I bought it.

Did you clean the crown of the piston before taking the pictures?  The carbon build up is a good indication of how the bike was running before taking it apart.

quote name='xtonycrx' timestamp='1334503632' post='9984970']
If that is a wiseco the exhaust side piston wall should have been drilled to help lubricate the exhaust bridge.  

I'd look closely at the exhaust bridge for wear. May consider more oil and a longer warm up cycle if there is wear.

+1 It looks like it wasn't getting enough lubrication on the piston on the exhaust bridge area of the cyl. causing the wear.   The person that changed the piston should've drilled the holes for better lubrication.   I'd check the cyl. for wear on the exhaust bridge area

xtonycrx, on 15 April 2012 - 07:27 AM, said:

Hondasforlife, on 15 April 2012 - 07:58 AM, said:

i think its very obvious what happened, these guys are on it.

I did clean the piston crown befor the picture. Before cleaning it had a nice even coating of black that when I peeled it off with a razor seemed about as thick a piece of paper and had the consistency of puty.  The cylinder looks pristene after skotch brite treatment.  Had a small streak where exhaust bridge lines up when i first took it apart but it wipped right off.  I will inspect the bridge closer and use a straight edge to look for wear before putting it back together. The head has a dark tan coating on it, but it has only been on for about 10 tanks of gas since i machined it and set the squish.  Plug was a dark brown.  It is going to get a stock piston put back in it.  I think i am going to go to 32:1 from 40:1.  The missing holes are the issue i think.  Looking forward to a little more low end when i get it back together.

Thanks for the sharp observations, you guys are on it.

you need to drill that piston. were the exhuast bridge is you need 2 small holes.

I am putting in a stock piston, it does not need the holes?

yes it does.

So does the stock honda piston out of the box need to be drilled?  Or does it already have the holes in it?

im not 100% sure. but if it isnt, it should have instructions how to do so.

Im pirtty sure only wiesco/forged pistons need too be drilled as they are not cast pistons, such as Prox/oem/namura..

You do need the holes too cool down the exhaust bridge if you run a forged piston, although im certain you dont need too with prox ect as they hold oil better as they are cast.

Although drilling the holes is quite easy and pritty hard too mess up if you're concerned, instructions come with the wiesco piston.

choppertown, on 15 April 2012 - 07:24 PM, said:

Third-Reef, on 15 April 2012 - 08:09 PM, said:

choppertown, on 15 April 2012 - 08:21 PM, said:

You do not need to drill any holes for cast pistons,  I highly doubt that it would cause any problems tho.  Choppertown, you should be careful giving advice on topics that you are not entirely sure about.  Could lead somebody down the wrong path.

Your exhaust bridge is likely "relieved" some anyway which gives you a bit pore clearance between the bridge and piston so you will not be able to tell if it is wore will a straight edge. I would just do a visual inspection to look for wear.

xtonycrx, on 16 April 2012 - 05:26 AM, said:

i know for a fact you need to drill the holes, well, you don't, but its recommended that you do. so, no. i will not watch out on giving advice that i know im right about.
cast of forged, the fact remains the exhaust bridge dose not get adiquite lubrication and over-heats in that spot easy without holes. the only thing im not sure about is if an OEM piston comes pre-drilled.

choppertown, on 16 April 2012 - 06:23 AM, said:

Please provide a reference that shows you are recommended to drill holes for any cast piston...

Third-Reef, on 15 April 2012 - 08:09 PM, said:

The stock piston does NOT need holes drilled in it.