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Author Topic: Analyze my piston  (Read 6604 times)

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Offline beaner

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Analyze my piston
« on: December 13, 2012, 03:14:03 AM »
04 RM 125.
Wiseco piston has been in the bike for 3 years, but I was hurt and hardly rode it for 2 of them. I installed a new ring last spring, and raced it at 6 events this past season, and probably a dozen practice days.  I rode it hard and it ran flawlessly. The ring is like new, and well within spec. The piston looks like new with the exception of the specs (looks like salt and pepper) on the top, but mostly concentrated on the top OD where it looks and feels like it's been glass beaded.
None of the previous 3 pistons in there looked like this, and I have made no changes. There was no indication of dirt or dust in the intake (it's all removed) and nothing unusual on the plug.



« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline msmola2002

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Analyze my piston
« Reply #1 on: December 13, 2012, 04:01:33 AM »
The pitting looks like detonation.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline factoryX

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Analyze my piston
« Reply #2 on: December 13, 2012, 04:26:23 AM »
What was the compression at? And what octane fuel were you running? Did you do a plug chop?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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I ride an 03 yz250, wait 04, wait 05, what ever, they're all the same #$@% YOU!

Offline beaner

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Analyze my piston
« Reply #3 on: December 13, 2012, 04:49:50 AM »
The compression is stock. The jetting is stock, and right on according to everything I've seen and read. SST pipe and FMF jetting recommendations are right on. The plug colour shows a little rich to my eye. 91 octane with 32-1 Maxima 927. Everything was covered in oil on teardown, and the piston looks like new everywhere else. No indication of detonation on the plug.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline msmola2002

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Analyze my piston
« Reply #4 on: December 13, 2012, 06:14:00 AM »
How was the coolant? Clean? Trans oil? Not milky? I had an O-ring leak on my RS and besides detonating its nuts off, it was ingesting water into the combustion chamber - piston was covered in pock marks that looked kinda like that!
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline TMKIWI

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Analyze my piston
« Reply #5 on: December 13, 2012, 06:49:31 AM »
Looks like water ingestion.
You may have a very small water leak , probably around the head o-rings.
Check underneath the piston as well. If there is any sign of water ( clean area's ) it could be coming from the base gasket.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline TotalNZ

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Analyze my piston
« Reply #6 on: December 13, 2012, 09:21:30 AM »
Yeah i'm thinking coolant getting into the combustion chamber too but i haven't seen it look like that.
I don't know how you can stand to run 91, mt bikes hate it the TM won't run on it.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline 2T Institute

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« Reply #7 on: December 13, 2012, 12:31:56 PM »
Squish band not working
Detonation occuring
Jetting rich
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline ford832

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Analyze my piston
« Reply #8 on: December 13, 2012, 01:20:51 PM »
Quote from: TotalNZ on December 13, 2012, 05:21:30 PM
Yeah i'm thinking coolant getting into the combustion chamber too but i haven't seen it look like that.
I don't know how you can stand to run 91, mt bikes hate it the TM won't run on it.

Looks like water ingestion to me as well.

91 octane is our supreme.You guys use RON ratings.We use an average of RON and MON-called AKI(anti knock index)It's usually written on the pumps as  (R+M)/2) That means our rating is about 3-4 points lower for the same fuel.Not as bad it sounds but we've recently had to have 10% ethanol in our regular and midgrade swill.(87 & 89)Fortunately,our supreme is still free of it-for now. :<img src=" title="Roll Eyes" class="smiley">
 
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline SachsGS

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Analyze my piston
« Reply #9 on: December 13, 2012, 03:41:20 PM »
What does the skirt of the piston look like (with a closeup of the ring land area)?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline beaner

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« Reply #10 on: December 13, 2012, 04:55:28 PM »
Coolant was full. Oil looks fine in the trans, and the bore, head, and combustion chamber look good. The piston otherwise looks perfect. It did not look like this last spring when I put the new ring in it. No indication of any leakage at the base gasket, or the head. Water ingestion from riding the bike after I'd just cleaned it maybe? I know the filter gets a little wet when I clean it, and I do use Notoil. It is possible that it might have gotten fairly wet during a marathon cleaning after a mud race, but riding it to the shop is only a few hundred meters away, and this is the first time I've seen this since I bought it in 07.

Thanks for the replies.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline ford832

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« Reply #11 on: December 13, 2012, 06:57:35 PM »
I had it happen once to me and I'm careful with the hose.Why once and never before?I don't know,but after that I pop the seat off and pull a plastic grocery bag over the filter before i wash it.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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Analyze my piston
« Reply #12 on: December 15, 2012, 09:04:40 AM »
The orange crap on the crown looks like ring blowby, but its on a certain area of the piston. This looks exactly like the vertex I took out of my CR125R. I still don't know what caused that cos the current one is fine. Could be debris in the ring grove.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline beaner

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« Reply #13 on: December 15, 2012, 12:08:08 PM »
Blowby on the top?

Anyway, I found something interesting when I pulled the head. It's not related, I'm sure but it looks like a casting defect, and some material may have come off and banged around a bit.  Typical Suzuki  :P I'll post a pic later.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline 2T Institute

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« Reply #14 on: December 15, 2012, 12:31:25 PM »
Quote from: Stusmoke on December 15, 2012, 05:04:40 PM
The orange crap on the crown looks like ring blowby, but its on a certain area of the piston.

It called a wash pattern, hotter areas of the piston cause the oil 'char' and stick to the piston , no charring no heat on the piston.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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