lean or detonation

[Riverratt]

Does the piston look like it was too lean or detonation? Motor is a 1985 XP 2.6 Timing was set at 25 deg, the idle jets are 33, the mids are 33 and the high speed are 71. I use 93 octane and Klotz oil.

[Riverratt]

more pics

[half fast]

Not sure but it looks wisecoish to me.Is it ? What was the piston to cyl fit ?Are you running t stats ? hf...

[stokernick]

I'd guess detonation,but more importantly,your wife says if you don't get that damned sh$t off her washing machine she's gonna stop doing laundry!

[Ro Yale]

From the piston skirts, looks like heat. But looking at the dome I would say detonation. Looks like major detonation and then was run a while after things had gone bad.
Later, Ro

[Riverratt]

Not sure but it looks wisecoish to me.Is it ? What was the piston to cyl fit ?Are you running t stats ? hf...
The piston is a factory omc. I am running the t stats and temp runs about 125

[Trikki1010]

I would lean toward detonation. Don't think you'd see that much carbon if it were that lean.

How tight were the holes:confused:

[EMDSAPMGR]

Has it ever been rebuilt? Do you know how many hours the engine has on it?

[chris_lacey]

I agree with Trikki Ricki.
Looks like pre-ignition detonation. Piston top doesn't look lean at all.

[Riverratt]

Has it ever been rebuilt? Do you know how many hours the engine has on it?
Yes 2 times this year so far.:mad: First time it cracked the sleeve in 3 places. This was a new sleeve, I backed off the timing and jetted the high speed up 1 size and I still have this problem. I indexed the flywheel when I put it together and checked to make sure all cylinders were firing at the right time and not double firing. This is the end result.

[Riverratt]

The motor had less than five hours on it. What will cause detonation besides timing which should not have been the issue at 25 deg set at 5000rpms

[terry taylor]

HI.Please provide more operating details full throttle[how long],midrange[hl]out of hole,prior engine sounds or stumble, did it stick, or knocking and turned off by key .oil injected?recent rebuild? is it possible bad or old gas some how ?It appears deto. damage but oily color may indicate term situation piston expansion of course is severe are all the same.? puzzling piston top with seemingly dark color and such damage.thanks sorry you already answerd some of my questions. Given what i see it was probably a piston to wall clearance on assemby the lubrication is apparently very good the apparent detonation damage on top because of good lube siezer would be slow as resistance built up top of piston took a slow beating thus the darker colors appears you had a slow siez er possibly from piston to wall clearance at build cross flows dont require closer tolerance as newer engines side t o side piston movement in bore with rings properly installed should be substantial I have built two and recommend syth. oil after break in. THANKS

[chris_lacey]

Ralph, did you check timing on each pair, or just number 1? I know I've had engines with as much as 3-4 degrees variation from highest to lowest timing.
This can be due to trigger variance, powerpack variance, spark plugs or spark plug wires.
Believe it or not, spark plug gap or internal resistance can account for several degrees of timing variation. I had to have this proven to me, but it's true, especially if the ignition system is a little weak. It takes longer for the system to jump the gap. This was shown to me by a GM engineer at their training center in Pickering, ON.


It's possible that the timing for #1 was at 25 BTDC, but some other could have easily been 28.
Something to look at.

[Riverratt]

I did not check the timing on the other cylinders. I was running Klotz synthetic when it happened. When I rebuild it this spring I broke it in with OMC oil then went to Synthetic. This time after hearing many big name engine builders that break in with the oil they are going to run I decided to start with klotz right away. The gas was not old plus I was running TK-7 additive as per recommendation of Tony Brucato and Wayne Tripp. The piston on top is not as black as it appears in the pictures.

[Riverratt]

Here is the thread from the first blow up this year.
http://forums.screamandfly.com/forums/showthread.php?t=107926

[racer]

That looks like a clearence problem that lead to increased piston heat as it started to scuff which resulted in detonation. What cyl is it? Timing needs to be checked on all 6 cylinders.

[terry taylor]

The motor had less than five hours on it. What will cause detonation besides timing which should not have been the issue at 25 deg set at 5000rpms
Combustion chamber temp, plug heat range, extreme comp.Ralph if you would respectfuly answer all my questions systematicly plus showing plug pics. and give heat range #,should be coldest available everyone might benifit and learn [just an example, engines turning consistent high rrrs if at all possible should be built with forged pistons.] We are here to help and to learn information is just so important not to ignore respectfuly THANKS.

[Riverratt]

That looks like a clearence problem that lead to increased piston heat as it started to scuff which resulted in detonation. What cyl is it? Timing needs to be checked on all 6 cylinders.
It is #4 same as the last time. How do you check the timing on #4 without the timing marks? Do you just find TDC and measure the marks on #1 and tranfer the marks?

[Riverratt]

The motor was turning about 5800 on a short burst and developed a knocking sound locked up as soon as I slowed down. I have been running factory omc pistons in the motor since 1994 and turning 6500rpms with no problems until this year. I had to hone the cylinders last fall because the exhaust gasket leaked water into #5 & #6 so I decided to freshen up and cleaned up the casting marks in the block. I had the carbs gone through and did know why all high speeds were 70 except for the middle carb being 73 so I rejetted the middle to 70 then blew up. I since changed all to 71 and blew up. Nothing else has changed but if it is detonation it cant be because I jetted down from 73 to 71 correct or is the lean what caused the heat. I will have to get the plug # and post a picture. I dont remeber off hand but they are the same #Autolite I have been using for years.
Terry please let me know if I did not answer any other questions. I did not realize I did not answer your questions.
Racer this is the same cylinder I talked to you earlier in the year about.

[BarryStrawn]

It is #4 same as the last time. How do you check the timing on #4 without the timing marks? Do you just find TDC and measure the marks on #1 and tranfer the marks?

Do you have a dial indicator? The most accurate way is to verify TDC on #1 and measure the piston drop at 25, 28 or whatever degrees you want. Then move your dial indicator to #4, zero it, turn crank to same piston drop and mark the flywheel.

[STVmod]

That looks like a clearence problem that lead to increased piston heat as it started to scuff which resulted in detonation. What cyl is it? Timing needs to be checked on all 6 cylinders.


I agree, what kind of skirt clearence are you runing on the pistons, looks like detonation on top but the increased heat could of caused the piston to stick if the skirt clearence wasent large enough to begin with.

[The Big Al]

Ok, My 2 cents!!!!

I say lean condition!

Now lean will create heat and detininatin.

But I say lean caused it, Piston skirt had a bad case of no oil!

The oil is in the fuel!

Lean on that cyc. No fuel or oil!!! Got hot, what little fuel it got cased the lean burn on the dome. Shirt was no oil! NONE!!

Check them carbs and fuel pressure!

[Lockjaw]

I read somewhere klotz was gritty oil. Sux about the piston. There was some talk a while back about breaking in with synthetic, and that it caused excessive heat buildup.

I would check those carbs out really good, and blow everything out with compressed air too.

Good luck. :D

[terry taylor]

HI. Would it be poss. to see pics. power head internals and cylinder heads and other pistons. In the 5 hours of use prior, any odd diferent increasing sounds or slowly increasing behaviour that may have given you thoughs maybe somthing isnt quite right. I think these things are formost in our mind after reassemble ,we all know finding the cause is at least some satisfaction .to a very difficult circumstance. THANKS.

[Riverratt]

Thanks for the input. I was away for the weekend and will try and get pics up of the cylinder and the other pistons as well.

[Trikki1010]

Thanks for the input. I was away for the weekend and will try and get pics up of the cylinder and the other pistons as well.

Isn't that BLACK motor on the pontoon still running:eek: ;)

[Riverratt]

Here are some pics of cyl # 1, 3 and 5

[Riverratt]

This is 2, 4, and 6

[The Big Al]

I have notes!!!!
http://forums.screamandfly.com/forums/attachment.php?attachmentid=114225&d=1157415274

[The Big Al]

Now we got a problem here!!!!!! Big time!!!!!!

http://forums.screamandfly.com/forums/attachment.php?attachmentid=114226&d=1157416204

[Riverratt]

#4 and the head

[Riverratt]

head and spark plug

[The Big Al]

This is a hard one, looks like no oil, no fuel. real dry.

Maybe just a small amount of fuel for heat. But no fuel or oil for that hole.

I wondering if the locate pin came out of the piston, ripped the ring out on the port wall, the the piston lost compression, then it could not pump fuel & oil and air in, then came the damage to the cyc wall and piston skirt?

[Riverratt]

The only other thing that bothers me is that I am still using a factory vro with the oil side plugged because with the saddle tanks and selector switch between the 2 tanks I can not get an electric fuel pump close enough to the tanks to work in my application. I have never had a problem using the factory pump before and was told that they supply more than enough fuel. I would think if it was not supplying enough fuel it would be the top carb going lean. :confused:

[terry taylor]

HI. Ralph I must say i feel my 1 st.account still stands .However pics. give good insight assembled piston to new cylinder insufficient clearance, hence the siez er even while being lubricated sufficiently [for normal clearance ],of course generated heat trasferred to combustion chamber putting resistence on plug [lighter color but does not appear melting to any degree.as you throttled back you heard distorted piston knocking.We can see amount of piston alluminum transferred to cylinder wall it took 5 hours running to accomplish this i believe. I covered this theory in my first post, I thought [flanged sleeve expansion rate thicker steel area top might factor in i dont know]. FIX/? You likely know quality bore, piston,clearance . Cylinders 1and2 are running a little hotter top cylinders usually do this clear and good cooling is all you can do , also i think putting the 73 s in top carb. would be good.Ag ain this my opinion hope it is as close to correct as i think it is P S.[IF YOU KEEP PERSONAL LABOUR RATE DOWN] you might save money.[ithink fuel supply o.k. [ WAIT THERES MORE]Use coldest plugs possible this keeps piston top temmperature lowest THANKS.

[Riverratt]

I am starting to agree about the clearance problem. I looked closer at my pictures and the actual piston and what looks like carbon buildup on top of the piston is actual large pieces of aluminum. The wrist pin was blue also and I had to really drive the wrist pin out because the side of the piston was peened melted over the hole.

[David Borg]

I had the same problem with a V4 140 Jono x flow , each time after about 8 hours of operation it blew a piston and it turned out to be lack of fuel pressure as the pick up in the tank was too small and at WOT there was never enough fuel supply.

[David - WI]

I am starting to agree about the clearance problem. I looked closer at my pictures and the actual piston and what looks like carbon buildup on top of the piston is actual large pieces of aluminum. The wrist pin was blue also and I had to really drive the wrist pin out because the side of the piston was peened melted over the hole.

It looks like maybe the head gasket leaked and the water took the oil off the cylinder wall. Then the piston got hot and started to cause it to detonate?

There doesn't seem to be enough damage to the spark plug or the piston top to account for the scoring on the skirt... it looks like the heat came up through the skirt and did it's damage there, and then the detonation started due to the hot piston just before you shut it down?

[bw1969]

I've burned up 2 xflows because the vro pumps don't seem to last very long with the oil line plugged off( one season for one and 2 seasons for the other). 2 different motors 2 different pumps switched to electric pump, no more problems.

[Trikki1010]

It looks like maybe the head gasket leaked and the water took the oil off the cylinder wall. Then the piston got hot and started to cause it to detonate?

I figured if it leaked water, the crown and head would have been steam cleaned, only reason I went to tolerances:confused:

[David - WI]

I figured if it leaked water, the crown and head would have been steam cleaned, only reason I went to tolerances:confused:

We put together a snowmobile motor that was a little bit "tight"... and after it seized up, I looked back and could still see the truck & trailer we took it off of! It seized several times that day and still didn't have the sort of damage that you have when we took it apart.

I don't see how you could possibly have put 5 hours on it if it was tight enough to overheat the piston and cause that failure?

I had a head gasket fail on my 200 Merc, and the piston came out "galled" all the way around like yours is. It was still getting fuel and spark... so it didn't get "cleaned" (it was still firing and making carbon/soot).

If you look at the piston marked "Chipped Crown" on this page, you can see the kind of scoring all the way around the piston that you appear to have: http://www.eric-gorr.com/tech/pistonguide.html

Your pistons have a thicker crown and the engine is probably running a little cooler than a dirt bike, so your piston didn't crack like his did... but the scoring and erosion on top look about the same.

For whatever it's worth. David

[The Big Al]

Check the deck and cyc hight, I notice the hot cyc sealing surface does not look the same as the others. This could be the problem, if cyc is low, the head gasket would not seal.

[terry taylor]

DAVID-WI Hi Your input is surely appreciated.Please allow me to answer your statement [Idont see how this engine would run for five hours if it was tight enough to over heat]. Could possibly be the amount of torque this engine produces 6 cylinders 150 or160 cubes with the good qualities of oil type could carry a dragging piston pretty good and poss. unnoticed till knocking from distortion set in.respectfuly [thanks]

[Trikki1010]

DAVID-WI Hi Your input is surely appreciated.Please allow me to answer your statement [Idont see how this engine would run for five hours if it was tight enough to over heat]. Could possibly be the amount of torque this engine produces 6 cylinders 150 or160 cubes with the good qualities of oil type could carry a dragging piston pretty good and poss. unnoticed till knocking from distortion set in.respectfuly [thanks]

This engine was loaded with oil for "Break-In", babied and not run up while in that period. This didn't show itself until it was wound out a bit...

I'm still with ya Terry

[David - WI]

DAVID-WI Hi Your input is surely appreciated.Please allow me to answer your statement [Idont see how this engine would run for five hours if it was tight enough to over heat]. Could possibly be the amount of torque this engine produces 6 cylinders 150 or160 cubes with the good qualities of oil type could carry a dragging piston pretty good and poss. unnoticed till knocking from distortion set in.respectfuly [thanks]

Possibly, but they usually pull the wrist pin out of the bottom of the piston and then shove it through the side of the block, if they have enough torque to keep turning when one piston gets stuck.

Take care, David

[Riverratt]

There was some orange rust like residue at the exhaust ports when I pulled it apart but it sat for about 2 weeks before I tore it down and just assumed the head gasket was deformed after all the heat. It wiped right off with my finger. When I got water in the cylinders before it always made a popping sound or affected performance so I dont think that was the case this time.

[David - WI]

This engine was loaded with oil for "Break-In", babied and not run up while in that period. This didn't show itself until it was wound out a bit...

I'm still with ya Terry

The scoring on the piston doesn't look like it came from being run too tight. It looks nothing like the "four-corner" or "multi-point" seizures shown on Eric Gorr's site (or any that I've ever seen).


http://www.eric-gorr.com/gfx/PHOPIS8.JPG http://www.eric-gorr.com/gfx/PHOPIS9.JPG


Your pictures aren't very clear, but the scoring on the piston skirt, erosion on the crown, and (what appear to be) places where the carbon was "popped" off the crown of the piston and the head seem to indicate there was water in the cylinder... like this one:


http://www.eric-gorr.com/gfx/PHOPIS5.JPG


You've had two virtually identical failures in the same cylinder since you put the new sleeve in it; do you & Terry think it's more likely that it was put together too tight twice... or that you have a bad seal like Big Al suggested?

I guess you'll know for sure when it comes apart the third time. No offense, but if it wasn't so expensive... this would be pretty funny. :o

Good luck with it, I have to get back to work. David

[Riverratt]

No the new sleeve was only this time. The new sleeve was needed after the first time. I dont see anything funny about it.

[The Big Al]

I think I would have that side of the block decked, I would do NOW!!!!

I think that's it, I really do, look at all the other 5 cyc at the top, white and sealed, that hole has burn on the top!

Al

[Riverratt]

I will have it decked again but it was decked when they installed the sleeve.

[Trikki1010]

I will have it decked again but it was decked when they installed the sleeve.

GIVE IN TO THE DARK SIDE ! ! !:eek: :eek: ;)

David-WI I would check alot of things if I were there, and I wouldn't have waited 2 weeks;)

The third photo looks pretty scored to me. I'm not there, just looking at photo's w/o a microscope:rolleyes:

[The Big Al]

Once you go black, you never go back!

[Riverratt]

Once you go black, you never go back!

I have a new black motor on my pontoon boat and all I can say is I am glad they come with a warranty because they has been in the shop alot this year also. Doesnt matter what color they are they are all gonna give you a headache sooner or latter and this year seems to be my year. The Evinrude has been turn key no problems for 10 years straight until this year. This year I have heard more booms from it then a fourth of July fireworks display.

[The Big Al]

I have a new black motor on my pontoon boat and all I can say is I am glad they come with a warranty because they has been in the shop alot this year also. Doesnt matter what color they are they are all gonna give you a headache sooner or latter and this year seems to be my year. The Evinrude has been turn key no problems for 10 years straight until this year. This year I have heard more booms from it then a fourth of July fireworks display.

Very true, but we got to gig ya! :D :D

[ToofastGMJ]

Hey Guys I am new to this site but I had to give my 2c worth. I have built a lot of turbocharged 2-stroke motors and from many years of experience burnin'em up through testing this looks like a leanout to me. What all the skirt scuffing is from is the rapid expansion of the piston, especially a fresh fit, causing it to score, and the oxidized burned aluminum pieces. Usually with detonation you will see more of the center of the piston burned out but in this case I see the leading edge of the squish crown burned along with the rest of the piston edge. This usually tells me a lean condition, especially with that one cyl. I see a couple of the other cylinders that look maybe a tad lean as well. Just my 2c. Oh yeh, I would never run Klotz in any of my motors! Then again, what do I know!