i just blew out the conrod and the piston and sleve assembly on my picco .12 nitro engine. I replaced the broken parts and now the piston gets stuck on the top of its rotation. i can turn the piston through the rotation but it is very hard. i have never broken in a new piston/ sleve assembly. I need help so i can get the beast running in time for spring. If i left any thing out i wil try to fil in the blanks. thanks for any help!
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picco piston gets stuck
- Thread starter cobraAVTC
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nitromaniac
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did you remember to replace any head shims, (if you have them) on that engine, without them the piston may just go up enough to cause it to stick, I have never heard of this,so I am going on a posibilty theory here, I really can't think of anything else that would cause the piston to stick that way, I am sure some one else may have some more input though!
May be its because of this read
The credit for this post gose to olds97_lss
Looking at the piston wont do you much good. Taking it apart is a last resort thing if you can't tell with the engine on the vehicle.
Clean the area around the glow plug thoroughly with a q-tip with alchohol or spray nitro cleaner down there with the plug in. Once clean, pull the plug out and rotate the crank shaft via the flywheel by hand when the engine is cold. You should feel some resistance as the piston gets close to the top. On a new engine, you probably can't turn it over with your finger.. On a used engine, if you don't feel any resistance, it's probably shot. This resistance is called piston/sleeve pinch. The inner diameter of the sleeve is actually smaller at the top than it is at the bottom. As the piston rises through the sleeve, it gets wedged and causes binding. This is how nitro engines are built to create an appropriate seal for compression.
No pinch = no seal = no compression = dieing/dead engine.
You can send your piston and sleeve somewhere to get them re-pinched for a smaller fee that probably what it costs new. From what I've read, they tend to last longer after being pinched again than they did when they were new. Check ebay for sleeve pinching.
Or, you may have just developed an air leak somwhere that is messing up the works. I'd first check for pinch, if there is any, pull off the carb and put some hightemp sensor safe automotive silicone around the neck (after cleaning it with alchohol and q-tips of course), put it back on and let it cure overnight. Also, pull the backplate off the engine and do the same to it where it seals to the crank case.
Also, you can first try leaning out the low speed needle. It may just be running to rich for the weather your driving in.
The credit for this post gose to olds97_lss
Looking at the piston wont do you much good. Taking it apart is a last resort thing if you can't tell with the engine on the vehicle.
Clean the area around the glow plug thoroughly with a q-tip with alchohol or spray nitro cleaner down there with the plug in. Once clean, pull the plug out and rotate the crank shaft via the flywheel by hand when the engine is cold. You should feel some resistance as the piston gets close to the top. On a new engine, you probably can't turn it over with your finger.. On a used engine, if you don't feel any resistance, it's probably shot. This resistance is called piston/sleeve pinch. The inner diameter of the sleeve is actually smaller at the top than it is at the bottom. As the piston rises through the sleeve, it gets wedged and causes binding. This is how nitro engines are built to create an appropriate seal for compression.
No pinch = no seal = no compression = dieing/dead engine.
You can send your piston and sleeve somewhere to get them re-pinched for a smaller fee that probably what it costs new. From what I've read, they tend to last longer after being pinched again than they did when they were new. Check ebay for sleeve pinching.
Or, you may have just developed an air leak somwhere that is messing up the works. I'd first check for pinch, if there is any, pull off the carb and put some hightemp sensor safe automotive silicone around the neck (after cleaning it with alchohol and q-tips of course), put it back on and let it cure overnight. Also, pull the backplate off the engine and do the same to it where it seals to the crank case.
Also, you can first try leaning out the low speed needle. It may just be running to rich for the weather your driving in.
dgrobe2112
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if the engine hasnt been broken in.. then it will stick at the top.. that is natural.. cuz of the tight pinch of the motor.. you will need to be patient.. have a good charged starter box.. with a good motor in it.. and a good ignitor.. turn you idle up so it will make it through the complete first tank.. after the 1st tank.. it should be ok
nitrotruckn
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Also.......
Did you oil the engine up good when you reassembled it?
Did you oil the engine up good when you reassembled it?
ZANDOR
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cobra have you try to start that mill yet?.if not try to put a few drops of aro in it and spin it over.oh and put heat to it w/ a hair dryer or heat gun. to help. just don't over heat it. i just went through this with a buddys hyp .21 8 port. we did get it going.it just took a while.....
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Honestly, it sounds normal. My engines were like that when new. The pinch at the top of the sleeve is what keeps your piston from making a full rotation without force. Before you start your break-in, put a couple of drops into the engine via the glowplug and give it a couple of yanks with the pullstart or spin it a little with the starterbox (do it without the plug installed). Reason being is that it is a new engine and has no lubrication in it.
Afterwards, install the plug and start your break-in.