Piston Messed Up

Predator303

Predator303

New Member
I got a question. I installed a new bottom end and used my old top end/piston because it was running extremely good.

I drove it for about 2 months and it was powerful all the way to the end (today). Couple days ago I turned up the screw on the carburator to get it to idle without turning off and I had to turn it all the way. After that the engine was way louder and seemed to burn much better but today the piston got stuck in one moment while I was driving just after turning it on.

When I took the head off, I could see a little hole in the side of the piston from the top and the spark as well as the inside of the combustion chamber and the top of the piston was all black with rust - guessing it was running too rich.

I also can see metal scratching down from either the piston or the walls when I look through the exhaust opening. The piston is still stuck and I have to hammer is out tomorrow when its day again so I can buy a new top end. I just hope the crankshaft or bearings didnt get any damage.

Anyways. Is is possible all that happened because I changed it too rich? I personally dont think that makes any sense. It also doesnt seem like the regular case like when its too lean and first you lose power and compression before the engine goes down. It ran perfect, smooth and a second later OFF and stuck.

I also run it with open exhaust but I also dont think thats the reason. Maybe it was just old. Next time I only use synthetic oil again.
 
open exhaust? nothing? buy a new motor and leave the pipe on. and keep the other for parts. to show what happens with open exhaust.[looks cool with the noise and flames piston parts flyin out]
 
without tearing it down, you're just guessing.

the obvious things would be a broken circlip, or the pin that keeps the rings from spinning broke out, or even a broken ring from improper assembly.

maybe the jug didn't align right with the bottom end, or maybe there was some crap in the case, or something fell in when you were putting it together.

ya gotta pull it apart to see what happened.

it doesn't sound like a heat seizure, meaning, it didn't melt and get stuck, it sounds like a chunk broke off and jammed it, got stuck in a bearing, or something like that.
 
yeah just did that. I cant even get it out completely but it looks like something between the rings broke off because above the exhaust hole there is a huge scratch, if you can still call it scratch where the piston got stuck. i saw a picture in here of parts breaking off between the piston rins so i am pretty sure its that because there is no way anything can get in there. it was running perfectly with full power for 2 months after using the new bottom end. luckily the crankshaft seems fine. i guess it was just old as **** and i really used it almost daily and for long trips.

is this the christian forum or why i cant even use the word h e l l in here??? wtf
 
One thing people do is put old clips back on a piston to hold the pin in place, which is a bad move. Always use new clips for maximum safety.
 
The little peg that keeps the rings in place may have come adrift, it's been known on engines with a much better reputation for quality.
 
Oh ok. Well the piston was the last thing that still could break. Everything else on that bike I replaced with new or custom parts. I should have just bought a new engine or make my own bike instead of building up a used one but at least I learned some new things again.
 
I'm buying something with a more modern design and hopefully better manufacture. The one thing I've learned from these forums is to avoid the upright motors at all costs.
 
this is the old bearing:

340508_342979072462341_221688127_o.jpg


unfortunately the NEW bottom end got some damage too so maybe its better to just get a new complete engine.

242925_342979209128994_1554984436_o.jpg
 
mine is a paper weight after 200 miles or so and it caused so many problems just to get to that point GT-5 needs to be redesigned
 
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