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Old 08-04-2014, 08:15 PM   #1
James2132   James2132 is offline
 
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Wow!! Unbelievable!!! You won't believe what just happened!!!

I was riding my scooter then all of a sudden there's this loud noise then scooter shuts off. When i took it Apart this is what I found. How did this happen?? http://postimg.org/image/szr413v9n/ http://postimg.org/image/wlnn5rwfx/



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Old 08-04-2014, 08:33 PM   #2
Admin   Admin is offline
 
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Image no worky. :(
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Old 08-04-2014, 09:36 PM   #3
James2132   James2132 is offline
 
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Old 08-04-2014, 09:36 PM   #4
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Old 08-04-2014, 09:39 PM   #5
James2132   James2132 is offline
 
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OMFG my valve is actually stuck in my piston!



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Old 08-05-2014, 07:56 AM   #6
cheapeto   cheapeto is offline
 
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Oh yeah, thats harsh.
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Old 08-05-2014, 08:38 AM   #7
James2132   James2132 is offline
 
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But why did this happen?
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Old 08-05-2014, 12:56 PM   #8
blueboy5000   blueboy5000 is offline
 
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Detonation most likely. What rpms do you regularly ride at?
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Old 08-05-2014, 02:55 PM   #9
James2132   James2132 is offline
 
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Like 6500 rpms
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Old 08-05-2014, 03:42 PM   #10
Houndguy   Houndguy is offline
 
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WTF

Wow! Talk about a failure.

OK, a few things come to mind and I am sure that I am probably wrong. After all I'm a monkey with a gun when it comes to mechanical things. But I do know something about physics.

1) What type of fuel were you using? If a higher octane than normal the more "blast" you would have. That compression could have blown a seal and forced the piston into it's current position.

2) Just a bad seal, it gave. Although I think you would have had some sort of warning sign before it got that far.

3) Somehow more fuel than normal was forced into the chamber, the ignition spark hits that higher than normal fuel ratio and BLAM. Although this is more commonly called a backfire or misfire.

4) Bad parts to begin with (and most likely the answer). How old was the scoot? What model? How many miles? All that matters but if I were to bet money on it I would say you had a hairline crack that expanded over time. Of course, again, there should have been some sign to that.

Anyhow...monkey with a gun so who the hell knows.
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Old 08-11-2014, 05:22 PM   #11
Swordsman   Swordsman is offline
 
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Quote:
Originally Posted by Houndguy View Post
1) What type of fuel were you using? If a higher octane than normal the more "blast" you would have. That compression could have blown a seal and forced the piston into it's current position.
I find this one extremely unlikely. Octane isn't increased in fuel grades for more power, it's increased to slow combustion so you don't get pre-detonation (aka spark knock or pinging) with more aggressive cam timing. Longer octane chains are slower to break down as they burn.

I suspect there was a valve clearance issue, maybe when it pulls the valve closed. If it got really tight, it might have popped the valve head off since they're not exactly quality materials. Isn't that the exhaust side? I know the exhaust valve on my Ural used to get tighter over time while my intake valve got looser. I assume it was from the heat.

Looks like there could be some wear around the break point also, but I have no idea how that would occur because I don't know how scooter valves are put together. Maybe that's just from it banging around inside the chamber before it battle-axed the piston.

~SM
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Old 08-11-2014, 07:12 PM   #12
kz1000st   kz1000st is offline
 
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The break is right at the spin weld. If you were only at 6,500 I suspect a bad weld. There's enough carbon to indicate a rich to normal burn. A defective valve is possible. Or the valve hung and got tagged.
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Old 08-19-2014, 09:28 AM   #13
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Quote:
Originally Posted by Swordsman View Post
I find this one extremely unlikely. Octane isn't increased in fuel grades for more power, it's increased to slow combustion so you don't get pre-detonation (aka spark knock or pinging) with more aggressive cam timing. Longer octane chains are slower to break down as they burn.

I suspect there was a valve clearance issue, maybe when it pulls the valve closed. If it got really tight, it might have popped the valve head off since they're not exactly quality materials. Isn't that the exhaust side? I know the exhaust valve on my Ural used to get tighter over time while my intake valve got looser. I assume it was from the heat.

Looks like there could be some wear around the break point also, but I have no idea how that would occur because I don't know how scooter valves are put together. Maybe that's just from it banging around inside the chamber before it battle-axed the piston.

~SM
TOTALLY agree!! and this is one of THE biggest misconceptions about high octane fuel! Folks believe higher octane = more power cause it burns faster. Yes Sir...you are correct..it burns slower as to prevent detonation in high compression engines. In my Scoots it actually decreases performance.. Folks say.. "But my manual says to use 91 octane or better" Here is where the confusion comes in.. Ya see..in European and Asian countries they use a different formula. They use RON only..which translates 91 octane in their gas to 87 octane in the U.S. where we use the (RON+MON)/2 formula. READ the little decal on your local gas station pump...it even says octane is based on (RON+MON)/2.. Here is a good link..a good read that should clear up the confusion on octane ratings that are posted so often on here. I have a 2003 Tank Urban Sporty 50 that has seen NOTHING but 87 for all of it's 21,200 miles so far. Whole engine is all original still...but is about due for rings..which is not bad for that much mileage. ok..the link..read and heed..
http://www.pencilgeek.org/2009/05/oc...nversions.html

In regards to your valve to piston collision...I have seen this a few times in my Scooter parts/repair shop. It is caused by a stretched timing chain and or a weak or defective chain tensioner. What happens is that the chain jumps or slips a few teeth on the Cam or Crankshaft gear...this causes it to jump valve timing so that the valve is open as the piston comes up. What appears as pitting or melting of the piston is actually just scarring from the broken metal pieces being scattered around... Just my 2 cents... I only work on Scooters for a living..so I may be wrong...
Glenn
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Old 08-07-2014, 08:45 AM   #14
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So what was it?
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Old 08-07-2014, 07:59 PM   #15
James2132   James2132 is offline
 
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I have no clue. I'm just gonna get a new cylinder, piston. And head. This is very strange. I've never of this happening before. My belt broke too. I guess when the motor locked up it broke thebelt
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