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/
|
Image no worky. :(
|
|
|
OMFG my valve is actually stuck in my piston!
|
Oh yeah, thats harsh.
|
But why did this happen?
|
Detonation most likely. What rpms do you regularly ride at?
|
Like 6500 rpms
|
Wow! Talk about a failure.
OK, a few things come to mind and I am sure that I am probably wrong. :nuts: 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. |
So what was it?
|
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
|
Oh and I enjoyed the 5 mile walk pushing the bike home! Lol
|
Quote:
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. >D ~SM |
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.
|
This happened to me too! My Il Bello (150cc) had about 2500 miles on it. Ran great!
This totally sux. http://i1371.photobucket.com/albums/...ps7fd5a907.jpg |
Although in MY case, clearly the piston melted as well.
|
Don't know caused these problems, or how scooters were operated/maintained....and of course, defective parts will cause catastrophic failure....however I feel that monitoring as much as possible, may catch an abnormal condition before something lets go.
So my scoot had it's speakers jerked out, and in the resulting holes, gauges were installed. Maybe not the best location for viewing while driving, but still more useful than speakers on a scooter.....and I would certainly notice high oil temps before melting the engine...Bob [IMG]http://i1271.photobucket.com/albums/...6/IMG_0081.jpg[/IMG] |
Not a bad idea.
|
Quote:
(You may notice I reference Urals a lot. They require a lot of tinkering, so it's the bike I have the most mechanical experience with! ;)) |
Quote:
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...:hmm: Glenn :) |
Great post Glen!!
|
Quote:
Glenn |
Quote:
Good post about octane. I've always understood octane to be resistance to ignition. My old Grand Wagoneer used to knock like crazy without premium. I run a 150cc GY6 and I've been putting premium in it all along. In fact, if you've seen my other posts, I've kind of obsessed about it. My question, I guess, is if higher octane means less pre-ignition, wouldn't that be a protection for your engine, especially at higher RPMs? |
Quote:
In regards to high octane..well if ya don't have pre-ignition I wouldn't see a need for it. But if it works for ya..use it...only costs a few pennies more per tank. In my Scoot it just seems to give less power. I used to own a Turbo Charged PT Cruiser and it HAD to have high octane..otherwise it sounded like VW diesel engine going down the road..:doh: I am not against high octane gas..I just wanted to let folks see and read that when their Asian manual says 91 octane..it is RON which equals 87 in U.S. gas. Cause many freak out or get frustrated when they can't find a gas station with 91 octane(U.S. grade gas) :scoot: |
Seems like defective valve to us!
|
Quote:
|
Classic "dropped valve" syndrome. Check to see If the valve retainer or keeper is still intact. Or is the valve spring broken? Somehow the retainers came loose and allowed the valve to "drop" and strike the piston until it snapped.
|
Hey Glen, when I first came to SD, like many I lurked for about a year before I registared, and ONE of the big fights going on back then (man I miss all that great info) was gas ratings and octane levels, and ethanol.
I always go do my own research for a thing, and man you nailed it!! |
Just so you don't feel bad about this take a gander at what happens to the high priced spread. How would you like to spend that much money and have this happen.
http://modernvespa.com/forum/topic130381.2 |
Quote:
A flat bed Tow is over $150 around here. Ernst |
Going with Flo really does work.
|
Was this scoot running a bbk? Any mods?
|
carasdad. I Agree completely, timing chain tension should be checked and adjusted as a maintenance item.
|
I also agree with the timing theory. If the timing is off it can mimic some of the fuel ratio theories and if it is really bad you can slam the valve and piston together (I think but don't know for sure that these are interference motors).
|
It looks to me like a classic case of metal mice infestation, the bite marks are plain to see on the head!
Jokes aside beside the previous ideas a too tight valve that runs hot due to not being able to get rid of it's heat to the seat will weaken the valve and possibly cause it to break as this one did. |
All times are GMT -4. The time now is 05:34 PM. |
Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.