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3.3 piston skirt breaking

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Bkyd Basher

Bkyd Basher

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hey, so weve had 2 piston skirts break in the last weak and a half, right near the exhaust cutout. Can anyone tell me why this happening or is it piss poor luck? First one the bearings are still fine with maybe like a gallon through it and the second had probably just over a gallon and a half and the front bearng fell apart in my hand!Please help!!
 
When mine do this I toss em and buy new. Not worth rebuilding over and over and multiple break ins stresses the bottom end a lot. Just replaced a 3.3 that was killing bearings and attempted a rebuild which wasted money.

There are numerous things that can cause it, bad piston or crank most likely I'm guessing.

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I'm just wondering if it has anything to do with the tune or something. I dont rebuild. I buy a new motor with no carb for 85.00
 
2 brand new engines and pistons broke on both?

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Get a decent motor - an OS or something.
It'll cost a fair bit more but work out cheaper in the long run & won't frustrate the cr@p out of you!
 
well i bought the picco max and that has given me the worst headache of all!! Well there not my motors that have done this. But 2 different guys i run with on the track.But i do all there wrenching for the most part. I have not had this happen to me in the 5 3.3s that I've bought and ran.Just can't figure out what would make this happen. Could the crank bearing be crappin out and causing it or what?
 
It is possible. If the bearing shreds its gonna send shrapnel up to piston for sure. Usually on the 3.3s its the rob snapping and taking skirt with it. I'm stumped at the fact you have had so many skirts break. Are they being run too lean maybe?
 
weird thing is also is the bearingsare fine inthe firsty one and only yhe front bearing is bad in the second. And on the second one the bearings fell out the front into my hand so they didnt make it through the motor.Possibly could be lean but they both had a nice smoke trail and were not hot. Then they smoked a real lot after the piston broke!!Wouldnt the top of the piston be more affected by a lean condition?
 
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Anything is possible and crazy things happen during manufacturing but for the skirt to break I would guess something got under the piston or it was weakened while being removed at one point. It's very easy for something to fall into the engine with the air filter or exhaust removed.
 
I actually just tore another one down tonight from this weekends races that just started sounding bad and not makin any power anymore. The rear crank bearing was not good, missing a ball and what not and after inspection of the piston i notice two hairline fractures in the same exact spot!!. Each side of the intake cutout. But after i saw that i looked at the glow plug element and it was gone also. So i am figureing that one was due to lean conditions. But as far as the other one with two perfectly fine bearings in it i do not know. Also the all have motor savers and the are ziptied tight also so idk. Stumped!!
 
I got a big container full of broken pistons, (skirts and wrist pin saddles) and rods from the 3.3...Trust me its a common occurance.
Time for you to move on to better things.
 
Yup...^^^ the longest life I've gotten out of a 3.3 was less than 5 gallons. and when that one let go I was just farting around in the front yard. Prior to the longest lasting 3.3 I went through 2 others. Now, well I've moved on. Talk your buddies into any model Novarossi engine. Even if its piped wrong, the durability is well worth it to have an engine that runs all day every day.
 
had the same thing happen to me, left the head shim off(noob mistake)..caused pre-detonation and bye bye piston! replaced the piston/sleeve/conrod, only to blow that one(front skirt this time) felt like a bad crank bearing..bought a picco .21 & am currently in the process of installing/converting. good luck!
 
have a look at the novarossi 2.5 its made for revo/t maxx and it dont cost much more than a new 3.3 and it comes with a manifold and pipe
 
Weird. I've had great luck with the
3.3. Do you oil it after every run? Keep an eye on temps?

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yup, i blow them off real good with air and make sure there is nothing in the head to fall in when i pull the plug to wd-40 it. Always lookin at the glow plug for color, clean and oil the filter and usually wash the filter housing as well. Never see any temps over 240-250. Idle and run great, good smoke trail also. I did notice on my revo that dirt gets packed up in behind the flywheel and in front of the bearing, which I'm sure isnt real good so i will be blowing that area out real well from now on also. Was actually thinkin of making something to fill that hole underneath the flywheel cause i do not use a the starter box. Like i said i just do not know.
 
Well it does happen. Nature of the hobby unfortunately. Guess I am just lucky...

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