Piston Guru's

[POWDERSLUT]

This is a piston outta a 800r with close to 5700 kms on it. It had a engine tech head with 13;5 to 1 comp.The other piston threw a ring but ,what are these perfect little circles from? Same marks on the dome,this was the pto side piston with the marks on the exhaust, pto side of the piston. I always use chevron 94 octane gas.

 

[maxwell]

that is cool! ive never seen anything like that. wtf....it must be debris...but what...........

 

[POWDERSLUT]

it was all cool till i had to tie it to, a m8 n get towed out...

 

[maxwell]

it was all cool till i had to tie it to, a m8 n get towed out...

LOL. wont hear the end of that one.

that has to be debris marks but i couldnt tell you what. its bizarre

 

[catf1000s/p]

if you r running 13 to 1 compression with only 94 octane fuel i would say is your problem, with that kind of compression you would need c-12 atleast, you really need to now if your compression is really 13 to 1 tho

 

[whitell]

looks like detonation, but also looks like there may have been some water in the fuel. that can cause the uniform pitting.

 

[POWDERSLUT]

13.5:1,but thats fine if i went to 14:1 then Art said i should be mixing in race gas.I only ride 3000 ft plus(thats the parking lot and when this low i baby it to at least 4500 ft),most is 5500-8000 ft range.

 

[heavy d]

I've seen pistons marked up with snow injestion........but not perfect little circles like that.....hmmmmm weird

 

[Kiwionsnow]

that looks like the end of your ring retainer in you ring land. (The pin that stops your ring from rotating on the piston). Or looking at it closer the end radius on your piston ring is gone, one side has a recess where this pin sits and the other end of the ring ( across the gap does not) You can see where it has broken off and worn a slot from the ring land grove through to the piston crown and poped up into the combustion chamber. If you look close you will see where the round dents start to be come square and then it was ejected out the exhaust. This failure is usally related to detonation but with 5000 km it owes you nothing. I run 14.1 RKtech head but the stock head is also 14.1. I also use the 94 with no trouble. I have had this failure before but I was on 87-89 octane in a pinch.

 

[scrfce]

Lucky u had a bud with an m8 there,,, cause i know that other xp woulda left ya buried in the trees. Now that thats outta the way lol, $hit looks funky dude, one of these guys ll have an idea, maybe modman.

 

[maxwell]

that looks like the end of your ring retainer in you ring land. (The pin that stops your ring from rotating on the piston). Or looking at it closer the end radius on your piston ring is gone, one side has a recess where this pin sits and the other end of the ring ( across the gap does not) You can see where it has broken off and worn a slot from the ring land grove through to the piston crown and poped up into the combustion chamber. If you look close you will see where the round dents start to be come square and then it was ejected out the exhaust. This failure is usally related to detonation but with 5000 km it owes you nothing. I run 14.1 RKtech head but the stock head is also 14.1. I also use the 94 with no trouble. I have had this failure before but I was on 87-89 octane in a pinch.

good point i can totally see that now. except my guess would be since that peice is flat perhaps it somehow worked itself into a ball either by heat or from bouncing around.

 

[maxwell]

hmm but one photo shows the end of the piston ring broken off in both locations.

 

[takethebounce]

Locater pin. I bet the circles match up perfect on the top of the piston and the head. The ends of the rings broke off with the pin worked its way out, caught the port, ended up on top of the piston and at 6000+ rpm, bounced around in there for a second and a half and ejected out and no longer looks like a pin.

 

[High Velocity]

X3 for ring locator pin. I've seen that on a few Doo's I've rebuilt.


Sent from my iPhone when I should be sledding.

 

[Shafty]

Mine 800 HO did the same exact same thing. X4 on the ring locator pin.

 

[CUSO]

You can see that the head and the piston is a mirror image. I am betting a pin also

Your lucky that a piston skirt didn't fail with those kinda K's

 

[tex78]

Could be a chunk from the bottom end. I guess u better account for the piston ring pins. If not u will have to dig deeper

 

[Slamnek]

Locator pin as well as a little detonation. I had a 13:5 rkt head on my 05 rev and had to run around 2L C111 for every 10L of prem or it would ping away. With 100LL av gas i had to use a little more.

 

[tukernater]

Locator pin as well as a little detonation. I had a 13:5 rkt head on my 05 rev and had to run around 2L C111 for every 10L of prem or it would ping away. With 100LL av gas i had to use a little more.

X2 the pin fell out because of det,run good fuel I've never turned a ring in any of my sleds.I sold my 03.5 rev with 7400 miles on it changed piston once little lean on NOS. Lol

 

[Modman]

yes, locator pin helped along with a little detonation. Other piston failed because of deto, ring caught the port after the pin fell out as well . same thing happened on both sides of the motor, only difference is the pin bounced around in this side. You can see the marks on the piston start exactly where the pin was located when it came loose. Because the same thing happened on both sides, its pretty much a sure sign that you do not have enough octane for your compression.