Third piston and still no resolution.

GoldenMotor.com

YesImLDS

Member
Jun 29, 2013
960
12
18
Columbia, Missouri
Hi guys, I have a problem I just can't seem to figure out. It all started with a retaining clip releasing itself and slamming between the piston and the wall. resulting in this:




Now I just bought another piston and wall and went on my way thinking it was resolved. About 300miles went by and the same problem came up. Missing retaining clip and a piston and wall terribly scratched. So I replaced them again thinking I might have caused the problem during installation. Well today I get everything set back up and ride about ten miles with no problems. I was even easing on it until it happened again, but this time. Retaining clips completely in place and the same problem.



Like I said I don't understand what is going on. The piston is completely scored once again, but the clips completely intact. Now the only thing I can think of is there was something in the crankcase that popped up through the transfer ports, but I thought that I cleaned it out to the best of my ability. It just doesn't make sense for this to happen three times in a row. Anybody know what could possibly cause this? Possibly slightly bent con rod? I am drawing a blank. Almost about to get another complete motor...
 

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
this is exactly why I don't replace top ends after a nasty failure unless a customer insists - no telling what debris is hiding somewhere down in the bottom or stuck to the wall of a transfer passage or blown back into the intake manifold or, or , or . . .
 

YesImLDS

Member
Jun 29, 2013
960
12
18
Columbia, Missouri
Well. The crankcase was cleaned, but I suppose there could be debris that I missed. It had to had gone thru the transfer ports. It's pushing me to just go get another bottom end, or complete motor
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
They were facing the intake side
Then we can rule that out.

This is going to be a tough one without actually having the engine in hand to look at it.
With the past failures I'm not sure I'd try another top end. I'd go with a new engine and keep that bad one around to study. If you're sure there was nothing left in the crankcase and the wrist pin snap rings were installed correctly we're grasping at straws here to determine a reason for these failures.

Hopefully later today someone else might offer a better diagnoses.

Tom
 

YesImLDS

Member
Jun 29, 2013
960
12
18
Columbia, Missouri
I think I may have found the problem. Found another piece of the old snap ring embedded in the piston. Probably need to open up the bottom end rehab it clean it the right way.... or just buy another engine.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
Splitting the cases is the only way to be sure it's clean after a failure like this. Rinsing is not good enough.
Also need to look for damage you can't see with jug off as all those chunks do not sit still when stuff breaks and you need to get ALL the debris.
I've found broken chunks in the bearings on engines rebuilt and run another thousand miles.
But you rarely get that lucky so when you blow a top end like this, tear it ALL the way down or risk the consequences.
 

Kioshk

Active Member
Oct 21, 2012
1,152
10
38
Connecticut
I'm with Maniac; get intimate with your China Girl. They're really simple once you get the hang of it. I highly recommend you get new case and cylinder-base gaskets before you split the case though. The gear-puller's your friend; be sure it's properly screwed-down before you draw the gears off to avoid stripping the tool. I always take the magneto off first to use as a magnet to hold all the screws, bolts, clips, washers, nuts, and woodruff keys. Also, a cheap rubber or plastic mallet is a good investment; it's handy for whacking the case open without damaging anything. You should also have some standard blue axle-grease handy for the clutch-spring cavity, and a dab for the clutch-sprockets when done.
 

Dan

Staff
May 25, 2008
12,765
115
48
58
Moosylvania
" I always take the magneto off first to use as a magnet to hold all the screws, bolts, clips, washers, nuts, and woodruff keys."

That's just dang cleaver, Kio. Very cool.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
I thought everyone did that? Heck I'll use a strip magnet even if the engine doesn't have one!
Never even occurred to me to mention it.
Been doing that on all motorcycles since age 16 when I learned it from my first real hot rod mechanic while hanging around bugging him.
 

Dan

Staff
May 25, 2008
12,765
115
48
58
Moosylvania
I thought everyone did that? Heck I'll use a strip magnet even if the engine doesn't have one!
Never even occurred to me to mention it.
Been doing that on all motorcycles since age 16 when I learned it from my first real hot rod mechanic while hanging around bugging him.
I got a harbor freight magnet dish, for free this month. Got another motor on the way to upgrade. Just bought a motor only on eBay to upgrade

I honestly never thought of that. Really great little trick, Manic.

YesIm, love them idiot magnet things. Have about 6 and they are strategically placed around my shop. One is on the fridge, lol.
HF has free 4" ones with coupons soon. Is tarps and flashlights right now.

Cool, new motor. New toys are always fun.
 

Dan

Staff
May 25, 2008
12,765
115
48
58
Moosylvania
cool!

Those things come in so handy and can be maddening loosing some tiny dang part.

I know we all secretly love/hate HF but just saw a mini bench grinder I bought there for $20, for $43 and 50 some thing on ebay and some where else. Northern tool now sells a 3-in-one machine for $1,600 that was closed out at HF for $800.

What cracks me up is these things get rated higher at higherend stores. The higher the price, the higher the rating. Sorry for the rant.....
 

Patchy

Member
Aug 12, 2014
87
0
6
California
I had this happen to me. You have to take the crank case apart and clean it, also sometimes those stupid clips don't like to sit in right.
 

YesImLDS

Member
Jun 29, 2013
960
12
18
Columbia, Missouri
I had this happen to me. You have to take the crank case apart and clean it, also sometimes those stupid clips don't like to sit in right.
Exactly what I believe to have happened. I didn't clean well enough to call it good. I need to crack open the crank case on the old motor to rebuild it once again because I have recently ordered a new motor and it won't be a bad experience as well as I could possibly get another bike going! Ha.