Engine failure pics- probable causes?

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Evans Ward
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Engine failure pics- probable causes?

#1 Post by Evans Ward » Wed Feb 07, 2018 11:09 am

Finally getting around to rebuilding my RZ engine. Failure happened about 2 yrs ago when flogging it and seemed to have lost right cylinder. Limped it home about 4 miles and definitely down on power. 11,000 miles on original bore/ pistons, stock timing, close to stock with mods in sig below. In looking at that right piston, can tell it got HOT as parts of the piston crown are missing. Upper ring there seems to be fused as well. Any guesses why this happened? Could it have been lack of oil lubrication with an oil pump failure? Cylinders are presently at Chuck Quenzler's shop in FL along with a set of OEM 1st over pistons for a bore job. Having him clean up the ports too and he'll also clearance the YPVS assembly. Hoping he'll be able to cut my he stock one piece head (he's considering it thinking on HG thickness/ application but head is not in his possession yet) to reshape combustion chambers/ set squish. I have a freshly rebuilt oil pump (by Arrow) that will go in with the rebuild along with a new OEM Banshee crankshaft. Wanting to learn from this failure. Pics below.
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84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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Evans Ward
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Re: Engine failure pics- probable causes?

#2 Post by Evans Ward » Wed Feb 07, 2018 11:10 am

More pics:
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84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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Evans Ward
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Re: Engine failure pics- probable causes?

#3 Post by Evans Ward » Wed Feb 07, 2018 11:12 am

More:
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84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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T.RexRacing
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Re: Engine failure pics- probable causes?

#4 Post by T.RexRacing » Wed Feb 07, 2018 11:43 am

From here it appears to be detonation. Could have progressed into pre-ignition.
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hondaror
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Re: Engine failure pics- probable causes?

#5 Post by hondaror » Wed Feb 07, 2018 11:54 am

Yeah, pre ignition and detonation go hand in hand. The detonation shows as piston damage around the edges of the piston. This is usually caused by pre ignition. The cylinder is firing before the spark and the two burn fronts collide. Something in the combustion chamber is glowing hot, causing the pre ignition. Could be something as simple as a scratch.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

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Evans Ward
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Re: Engine failure pics- probable causes?

#6 Post by Evans Ward » Wed Feb 07, 2018 12:40 pm

Thanks guys! Was also running stock recommended NGK plugs.

If I don't get the head cut, I will go with this nice 1985 original 31K head I purchased off eBay:
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84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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Re: Engine failure pics- probable causes?

#7 Post by hondaror » Wed Feb 07, 2018 8:07 pm

My old eyes sense that your "new" head has previously been cut.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

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Evans Ward
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Re: Engine failure pics- probable causes?

#8 Post by Evans Ward » Wed Feb 07, 2018 8:15 pm

hondaror wrote:My old eyes sense that your "new" head has previously been cut.
Sounds like I better use the newly bought one as the cut one. Is there a way to measure and know how much it may have been cut? It was sold/ misrepresented as a virgin head.
84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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Re: Engine failure pics- probable causes?

#9 Post by hondaror » Wed Feb 07, 2018 8:18 pm

There should be a very distinct lip off the deck to the combustion chamber. Someone will have the spec. I'm 950 kms from home at the moment.
From the looks of it, I'd say about 0.020". The area of the YPVS logo has been cut. It could be as much as 0.040".
What really matters is the squish.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

hablair
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Re: Engine failure pics- probable causes?

#10 Post by hablair » Thu Feb 08, 2018 10:07 am

Definitely not a lack of oil, you would have scoring on the skirts 45 degrees to the gudgeon pin

The head has definitely been machined you can see the shadows of the old head gasket

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2smoke
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Re: Engine failure pics- probable causes?

#11 Post by 2smoke » Thu Feb 08, 2018 1:00 pm

Is the old head corroded under that gasket?
It would be worth the time to check the thermostat operation too.
Colin
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Evans Ward
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Re: Engine failure pics- probable causes?

#12 Post by Evans Ward » Thu Feb 08, 2018 7:54 pm

2smoke wrote:Is the old head corroded under that gasket?
It would be worth the time to check the thermostat operation too.

Thanks for the observation and will check that. I'll also boil the t stat and see if it opens. Appreciate the insight! :smt023
84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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Re: Engine failure pics- probable causes?

#13 Post by evansje1 » Thu Feb 08, 2018 9:27 pm

I see the problem, trying to out run me :smt005 :smt035
1973 RD350
2014 Suzuki DT1000
1979 RD400F Daytona Special
1984 RZ350

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Evans Ward
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Re: Engine failure pics- probable causes?

#14 Post by Evans Ward » Thu Feb 08, 2018 9:43 pm

evansje1 wrote:I see the problem, trying to out run me :smt005 :smt035
You've blown my cover! :smt009 :smt047
84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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Evans Ward
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Re: Engine failure pics- probable causes?

#15 Post by Evans Ward » Mon Feb 26, 2018 6:58 pm

Got a call from Chuck Supertune Quenzler who is boring my cylinders. 1st over won't cut it as it will need to be bored 2nd over- motor was tired for sure. Going with Pro-X pistons. He will move on to head work for me after the bore job.
84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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