What normally causes ring failure? - Triumph675.Net Forums
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post #1 of 12 Old 06-26-17, 18:09 Thread Starter
mszilves
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What normally causes ring failure?

So last Friday was a practice day before our 4th race round this season. Rode the bike for 2 sessions, felt pretty much normal. Went to start the bike up for the 3rd session, and it was hard to start. After it started, had a hard time idling, and sounded like it was missing a cylinder.

Long story short, we tested compression and found the #1 cylinder had ~50PSI vs normal ~160. Checked valve clearances were ok, and no signs of anything coming out of the exhaust, so we are leaning towards ring failure. Especially since there was a lot of blowby coming out of the crankcase breather hose, and airbox was soaking wet with oil/fuel mix.

What would normally cause a ring failure, and would it happen all of a sudden or over time? Looking for experience from your racers/track day guys out there.

"It was the kind of situation that regularly sees many of the people who masquerade as motorcyclists and ride every third Sunday up their favourite local road (if it's sunny) to sit at a cafe and make broom broom noises with other pretend-motorcyclist-idiots, crash their brains out."
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Last edited by mszilves; 06-27-17 at 01:35.
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post #2 of 12 Old 06-27-17, 00:18
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My guesses would be:

Running too lean
wheelies
got too hot?
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post #3 of 12 Old 06-27-17, 00:49
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Near impossible to tell without seeing the insides first, and even then sometimes its a crap shoot.
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post #4 of 12 Old 06-27-17, 01:22
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Quote:
Originally Posted by Shamrock View Post
wheelies
100% this.
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post #5 of 12 Old 07-11-17, 00:36 Thread Starter
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Update: So we got a new engine installed last weekend, and had the bike to the tuner to make sure fueling was dialed in.

After breaking it in, and running it, he noticed there was a drop in power between 7-8K as well as the top end was down on power and also dropping off early. Right away he suggested there was an air issue.

Since the air filter was new, we looked at the exhaust. I am running the stock header with a Hindle slip-on.

The cat was not only plugged, it was sitting cocked inside the chamber, most likely from a crash. It is not welded in, only press fit.

Took an air chisel and pliers to it, and removed the cat honeycomb guts. The stock header is now open.




What we found could definitely explain the failed cylinder on the original engine! We think itís likely that it was so plugged up that it couldíve overheated the original engine and burned the rings. All data says that Cylinder #1 is usually the one that goes in case of overheating.

Will report back when we open the engine up, but for now at least the new one shouldnít suffer the same fate. So if you are running the stock catted header for racing, either get a full system or get rid of the cat ASAP!

"It was the kind of situation that regularly sees many of the people who masquerade as motorcyclists and ride every third Sunday up their favourite local road (if it's sunny) to sit at a cafe and make broom broom noises with other pretend-motorcyclist-idiots, crash their brains out."
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post #6 of 12 Old 07-14-17, 01:06
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Quote:
Originally Posted by Shamrock View Post
My guesses would be:

Running too lean
wheelies
got too hot?
What does wheelies have to do with it?

if 1 cylinder fails its due to that one cylinder malfunctioning, oil related which is ring issue.
Your bike is injected with a fuel rail...
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post #7 of 12 Old 07-14-17, 01:10
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Quote:
Originally Posted by Buddy
What does wheelies have to do with it?

if 1 cylinder fails its due to that one cylinder malfunctioning, oil related which is ring issue.
Your bike is injected with a fuel rail...
When one wheelies, you temporarily starve the rings and the oil pump of oil. Have you never seen a ring failure while wheeling? Smoke will bellow out of the exhaust. Even @MGFChapin agreed with me.
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post #8 of 12 Old 07-14-17, 01:16
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Quote:
Originally Posted by Shamrock View Post
When one wheelies, you temporarily starve the rings and the oil pump of oil. Have you never seen a ring failure while wheeling? Smoke will bellow out of the exhaust. Even @MGFChapin agreed with me.
Jesus man. What are you talking about...

1. thats caused in Vtwins. SV, ducatis, and you have to ride a wheelie for about a mile for that to even occur.
2. the sump for all inlines are in the middle (or towards the rear). It will not STARVE. why do smart people engineer it this way? because its called acceleration. Would a smart japanese guy engineer the sump to be in the FRONT so everytime you Accelerate or do the tiniest wheelie you starve of oil?

Have you ever built a motorcycle engine? did a 675 ever blow up from wheelies? too many questions
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post #9 of 12 Old 07-14-17, 01:20
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Also a fuel rail is a rail for this one purpose. Direct injecting with equal fuel pressure, minimizing multi cylinder difference. Injector failure is rare, and if they do fail...it will flood not lean on 99% of cases.

SO argument and joking aside, check the mixture. It was probably running too lean or knocking across all 3 cylinders, and one just gave out...

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post #10 of 12 Old 07-14-17, 01:29
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So, all you saw in this entire thread, was my "wheelies" WORD. Did you not SEE the three WORDS I put ahead of it, ON TOP?

Running too lean!

Also pay attention. After I and 4 others posted, the OP went back and edited the post. Also, the OP listed the reason for the burnt piston. It was the catalytic converter loosened and fell sideways.

Also, yes, I have seen an engine blow up while doing a wheelie TWICE. Suzuki GSXR750 and 2008 R6.

Quote:
Would a smart japanese guy engineer the sump to be in the FRONT so everytime you Accelerate or do the tiniest wheelie you starve of oil?
Since when is Triumph Japanese?
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