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Post by johnnycanuck on Jul 24, 2015 16:10:05 GMT -5
Hello,
Couldn't find a specific CPI section so if this post has to be moved to it proper location - sorry.
The piston has a hole in it. What may have caused this? I have removed engine from frame and noticed that the crankshaft spline are worn on the side where the variator is. The matching groves on the variator have play when on the crankshaft and so I will have to probably install and new crankshaft. How does one separate the engine so as to remove the crankshaft? The piston cylinder and head don't appear to be scored or scratched. Should I just get these new also? I wish I could just buy a complete rebuilt engine, it would probably cost the same or less.
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Post by scooterpimp on Jul 24, 2015 16:40:14 GMT -5
Holy piston = hot, lean , preignition etc. condition if its a melted hole. Good time for some tech. Section reading., a rebuild can be done fairly inexpensively if keeping stock., new 2t engines are hard to find & can be pricey.
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Post by johnnycanuck on Jul 24, 2015 22:44:46 GMT -5
I figured that the scooter was running lean. I am just going to buy a new carb. Can you direct me to where I can find a youtube video or a step by step process to removing the crankshaft?
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Post by niz76 on Jul 25, 2015 0:57:36 GMT -5
Buying a new carb isn't neccesarily going to solve your lean tune, unless it somehow miraculously had just the right jet and needle setting in it... You'll need to find out what jet was in the carb when it melted the piston and tune from there. Besides, buying $15 worth of jets to tune with is cheaper than replacing the carb and flying blind and then tearing the engine down again after it melts the second time. Gotta tune that carb correct! There's a ton of carb tuning info and even crank changing videos in the Tech library!
P.s> There are other conditions that can also lead to a holed piston such as air leaks that lean out your mix etc...
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Post by johnnycanuck on Jul 25, 2015 16:56:40 GMT -5
thanks!! I went to the tech section - very informative. I am wondering if maybe the oil pump malfunctioned? The carburetor is the stock carb, I guess I can just clean it and put a new carb kit in it.
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Post by scooterpimp on Jul 25, 2015 17:04:33 GMT -5
Oil pump failure usually ends up in engine siezure , rebuild your carb is only good if you properly jet carb to prevent lean condition/siezures etc. In the future. If that was cause of piston failure.
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Post by Lucass2T on Jul 26, 2015 9:55:44 GMT -5
You gotta do a damn good job if you want to burn a hole in a (fairly) stock engine.
I think it was a lean mixture. I haven't seen you talking about altering ignition timing or compression so that leaves a lean carb setting.
I'd suggest to swap the main jet for one thats 10 sizes bigger en work from there.
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Post by iwiketuddlz on Jul 26, 2015 10:16:08 GMT -5
Post a pic?? Can't say I have seen to many holes in Pistons!!!
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Post by johnnycanuck on Jul 30, 2015 15:24:06 GMT -5
I will post a picture soon the piston is at my father's garage.
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Post by niz76 on Jul 31, 2015 0:07:08 GMT -5
Post a pic?? Can't say I have seen to many holes in Pistons!!! Here ya go Tuddlz. This is from my Roketa AIR build thread..
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Post by filip on Jul 31, 2015 5:19:29 GMT -5
In some rare cases the spark plug can cause this
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Post by Lucass2T on Jul 31, 2015 8:29:56 GMT -5
This is a 70cc, not a stock motor. But man, holy crap. Didn't you notice 'something' just before it blew? The engine must've been telling you something because this doesn't just happen.
So: Lean jetting? Too warm heat range plug? Ignition wayyy off? Bad gas (low octane number)? Air leaks?
Btw, have you been using a piston stop?
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Post by derbiman on Jul 31, 2015 8:46:27 GMT -5
Wow, that is a large hole. Why do the edges of the hole not look melted? It looks more like it was broken out with force of some sort.
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Post by iwiketuddlz on Jul 31, 2015 11:42:22 GMT -5
Holy shit niz!!! That's some crazy shit right there.... Thanks good sir!!!!!
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Post by Lucass2T on Jul 31, 2015 11:42:49 GMT -5
Wow, that is a large hole. Why do the edges of the hole not look melted? It looks more like it was broken out with force of some sort. Because of that the question about the piston stop
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