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Post by humanshield on Jun 7, 2015 17:18:59 GMT -5
So I have a 150cc motor I'm working on. It ran just moments before I took the valve cover off....but noisy. I was like...hmmmm...that don't sound right ? Here is the way I found the Rocker assembly.  The bad news is I need a new rocker assembly The worse news is the valve "may" have hit the head to cause this damage The WORST news is that that missing piece seems to have ended up in the crankcase because I cant find it !   |
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Post by Silar on Jun 8, 2015 4:55:59 GMT -5
Yikes!
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Post by katastroff on Jun 8, 2015 5:03:01 GMT -5
No better word could describe this.  |
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Post by scooterpimp on Jun 8, 2015 6:12:33 GMT -5
Crack kills
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Post by humanshield on Jun 8, 2015 6:53:20 GMT -5
When I Google this, I can't find any other examples of this happening  Only thing I can think of off the bat is the valve must have hit the piston to do that (unless) there was a batch of very badly cast rocker arm assemblies out of Chiner. But It runs....guess I can find out if I pull the head. Other strange thing is there must have been 3/16" to maybe 1/4" inch play between the intake valve cam lobe and the valve tappet...and yet it started every time and would run I guess I better I pull the head and check the valves and piston. Wonder if that missing piece could have worked it's way to the drain hole. |
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Post by runningbuck on Jun 8, 2015 9:58:00 GMT -5
it appears that something was off before you started the motor and you see the ending result I had a rocker are that did not want to tighten up right found that the arm was not lined up right had to loosen the nuts up re a line every thing up but that was just me
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Post by Fox on Jun 8, 2015 10:32:48 GMT -5
I doubt it had anything to do with a clearance issue. It's just another Chinese part failing.Just put a new rocker assy. and run it. That little metal chip will most likely find itself a little nook on the bottom of the crank case and stay there.
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Post by humanshield on Jun 8, 2015 11:37:56 GMT -5
I doubt it had anything to do with a clearance issue. It's just another Chinese part failing.Just put a new rocker assy. and run it. That little metal chip will most likely find itself a little nook on the bottom of the crank case and stay there. I like this answer  |
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Post by Elektrey on Jun 8, 2015 12:28:54 GMT -5
1500cc is probably too much to put on those small little rocker arms |
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Post by scooterpimp on Jun 8, 2015 19:29:06 GMT -5
1500cc is probably too much to put on those small little rocker arms Dang , i was gonna say the same thing!lol. |
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Post by humanshield on Jun 8, 2015 21:06:39 GMT -5
1500cc is probably too much to put on those small little rocker arms What, you think I'm gonna mess around with dinky 100cc kits? pfffft  |
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Post by humanshield on Jun 16, 2015 14:44:41 GMT -5
Well...been thinking about this broken rocker assembly and it's not something you hear about much. I'm kinda tending to believe "something" bound up and caused it. Could have been a valve seizing in the guide. But it's the intake valve so that's less likely. If it was the exhaust valve I'd say probably that.
Gonna pull the head and make sure it wasn't a piston / valve whack. Doubt it.
I guess better to assume it had a cause other than rocker assembly failure...unless I had other people chime in and say they've seen these rocker assemblies just fail like this....but they haven't.
Hope this info helps someone down the road.
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Post by humanshield on Jun 18, 2015 12:34:41 GMT -5
Follow up...
After taking the head off and removing the valve to check for guide issues, broken springs, interference etc...
Nothing. Not even a little nothing.
There is absolutely nothing there that would indicate a cause for the fractured rocker arm assembly.
SO, it seems like those who said it was due to "cheap Chinese parts" were right.
Dismal to think a rocker assembly could just fracture like that under normal use.
The casting quality control must be really poor or non existent.
Ok..adding rocker arm assembly to the spare parts I have to carry on extended road trips (sheeesh)
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Post by Fox on Jun 18, 2015 13:07:45 GMT -5
I have broken two rocker assy's in the past from over-torquing the head nuts. They didn't break like yours did but they are brittle and they are subject to a lot of vibration and stress. Like when you rev the engine really high on the stand and then jam on the rear brake. The engine slows down really fast so you get stress on the cam chain and cam bearings and the rocker assy. holds the cam down.
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Post by humanshield on Jun 18, 2015 15:00:04 GMT -5
Ok. Just looking for more info since I didn't find anything obvious to cause this. Of course, I have no idea how it was treated before I got it.
Maybe someone over torqued the head nuts before I got it. It's possible. An interesting side note is that at least one of the 4 studs was loose and could be turned by hand. I intend to Loctite them going back in.
Are the two broken ones on a 150cc ?
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