# Piston stuck at top dead center



## 1gr8bldr (Jan 8, 2017)

Trying to get my built 400 2 stroke Scrambler 4x4 back going after getting it back from being stolen. I fixed the ignition that they stripped by using another from a parts bike. I don't know what they did to it. They tried to crank it and abandoned it after giving up on it, leaving it 1/4 mile behind my house. Now I see that the motor is locked????? I pulled the head. It was stuck on the upward travel just shy of the top. I tapped and pushed finially getting it to move, meaning the rings are not stuck or... no longer stuck. I then gave the pull cord a strong tug. It climbed 1 inch and stopped at top dead center. A bad place. Perfect top does not like to be tapped on. Any ideas? Was not wanting to take off the cover to the flywheel due to everything else that has to come off. Any tricks of the trade?


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## NE GA Pappy (Jan 8, 2017)

get an adaptor and put air pressure on it thru the sparkplug hole after you put some brakefluid down in it.  Brakefluid will help break it loose and air will move it down from the TDC position


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## pavogrande (Jan 8, 2017)

put it in gear and give it a bump or two


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## 1gr8bldr (Jan 9, 2017)

pavogrande said:


> put it in gear and give it a bump or two


It has an auto transmission..... wonder if it were work the same? I'll try


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## 1gr8bldr (Jan 9, 2017)

NE GA Pappy said:


> get an adaptor and put air pressure on it thru the sparkplug hole after you put some brakefluid down in it.  Brakefluid will help break it loose and air will move it down from the TDC position


It has moved so I don't think the rings are rusted to the cylinder. And I can get the piston to rock if you can call it that.... it will move within it's cylinder within the tolerance of the bore. If it were not top dead center, I would bump it with a block and hammer, but its at that point where the force could effect the wrist pin rather than the crank rotate. I don't have an adapter, otherwise that sounds like a safe way to put some pressure.


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## 1gr8bldr (Jan 9, 2017)

1gr8bldr said:


> It has an auto transmission..... wonder if it were work the same? I'll try





pavogrande said:


> put it in gear and give it a bump or two


 I was thinking about this. The auto has a belt that is loose until the rpm's climb


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## pavogrande (Jan 9, 2017)

If the head is off -- oil it up good an tap it with a wood block anyway -  good chance it is not on exact dead center  --
air is only good till the exhaust port is exposed  -

An adapter can be made from an old plug and a pipe nipple --


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## 1gr8bldr (Jan 10, 2017)

I pulled the cylinder off. As some know, you have to strip about everything. The crank did not want to turn. I shot some oil in on top of the crank. Took a screw driver and levered the crank back in forth to loosen it up. It soon began to move so I held the piston straight and pulled the pull cord. It began to move. I shot more oil in on the crank and now it moves good. I am not sure what I want to do at this point. Apparently when they stole the machine, after pushing it far enough away from my house, they tried for a long while to crank it. Little did they know the fuel was cut off. This on a 2 stroke is bad news. No lubrication from the fuel /OIL mix. They thought it was on but I had bypassed the fuel petock because it leaked and added another. The old Polaris's has an extension that reaches back to the petcock. This extension still in place but not enguaging the new petcock. So they turned it over and over without any oil getting to the bearings. They were dry as a bone. The crank and piston has a black smudge that now needs to be cleaned off. I think I will flush the case out with diesel fuel. I suppose I will put it all back together. I just so happen to have everything to rebuild it completely. But I don't really want to. All these high performance parts are for another 400 that I have ready to rebuild when I find time. Bored and ported cylinder, lightened flywheel, bored carb, new crank and bearings, lighter piston, etc. I will have to rob the gaskets. I am hesitant not to tear it apart clean  and replace everything. That's alot of trouble, yet if it comes apart 10 hours from now, then I will wish I had. Shame though, this motor only had 1 hour on it since I rebuilt it until they trashed it.


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## rjcruiser (Jan 10, 2017)

1gr8bldr said:


> I pulled the cylinder off. As some know, you have to strip about everything. The crank did not want to turn. I shot some oil in on top of the crank. Took a screw driver and levered the crank back in forth to loosen it up. It soon began to move so I held the piston straight and pulled the pull cord. It began to move. I shot more oil in on the crank and now it moves good. I am not sure what I want to do at this point. Apparently when they stole the machine, after pushing it far enough away from my house, they tried for a long while to crank it. Little did they know the fuel was cut off. This on a 2 stroke is bad news. No lubrication from the fuel /OIL mix. They thought it was on but I had bypassed the fuel petock because it leaked and added another. The old Polaris's has an extension that reaches back to the petcock. This extension still in place but not enguaging the new petcock. So they turned it over and over without any oil getting to the bearings. They were dry as a bone. The crank and piston has a black smudge that now needs to be cleaned off. I think I will flush the case out with diesel fuel. I suppose I will put it all back together. I just so happen to have everything to rebuild it completely. But I don't really want to. All these high performance parts are for another 400 that I have ready to rebuild when I find time. Bored and ported cylinder, lightened flywheel, bored carb, new crank and bearings, lighter piston, etc. I will have to rob the gaskets. I am hesitant not to tear it apart clean  and replace everything. That's alot of trouble, yet if it comes apart 10 hours from now, then I will wish I had. Shame though, this motor only had 1 hour on it since I rebuilt it until they trashed it.



Sorry to hear about the theft...but did you at least get insurance money to replace it?

If you have another one ready to go...maybe just sell this one for parts...or part it out...or use it as a parts machine for your other one you're about to rebuild.


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## 1gr8bldr (Jan 10, 2017)

rjcruiser said:


> Sorry to hear about the theft...but did you at least get insurance money to replace it?
> 
> If you have another one ready to go...maybe just sell this one for parts...or part it out...or use it as a parts machine for your other one you're about to rebuild.


I had planned on having 2. I have always had utility 4 wheelers, loaded with basket racks, lacking suspension. I never knew how much fun a sport 4 wheeler was. I wanted  this 95 Scrambler partly because I like older stuff, taking as much pride in it being rare and different than someone with these newer $10,000 machines. Plus, it lacked all these sensors and such, therefore I can work on it. It was so much fun compared to the typical utility ATV. Sooooooo, I found another.... sold as a parts bike been sitting for years in the rain with the cylinder off. LOL, so I decided to build it as well. From a $200 rust rucked to a built motor with 30 inch mudders, yet still light weight, nibble and quick. That is the goal.  Will start it soon. One sport and one mudder. LOL, I sound like a teenager. My motive is to spend time with my 16 year old. We built him a mudder last year and he has a sport Scrambler. His is a 500 4stroke. Does not have the raw power of my 400 but much more user friendly for a 50 year old


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## rjcruiser (Jan 11, 2017)

1gr8bldr said:


> I had planned on having 2. I have always had utility 4 wheelers, loaded with basket racks, lacking suspension. I never knew how much fun a sport 4 wheeler was. I wanted  this 95 Scrambler partly because I like older stuff, taking as much pride in it being rare and different than someone with these newer $10,000 machines. Plus, it lacked all these sensors and such, therefore I can work on it. It was so much fun compared to the typical utility ATV. Sooooooo, I found another.... sold as a parts bike been sitting for years in the rain with the cylinder off. LOL, so I decided to build it as well. From a $200 rust rucked to a built motor with 30 inch mudders, yet still light weight, nibble and quick. That is the goal.  Will start it soon. One sport and one mudder. LOL, I sound like a teenager. My motive is to spend time with my 16 year old. We built him a mudder last year and he has a sport Scrambler. His is a 500 4stroke. Does not have the raw power of my 400 but much more user friendly for a 50 year old



Then...it sounds like you know what has to be done.  

Look at the bright side...more shop time spent with your son.


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## Artfuldodger (Jan 11, 2017)

I'd just put it back together and try it. Does it have an oil injector pump or do you mix the oil and gas? I was wondering if it would get any lubrication from an injector if one tried & tried to crank it with the fuel cock off?


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## 1gr8bldr (Jan 11, 2017)

Artfuldodger said:


> I'd just put it back together and try it. Does it have an oil injector pump or do you mix the oil and gas? I was wondering if it would get any lubrication from an injector if one tried & tried to crank it with the fuel cock off?


LOL, I bypassed the oil injector pump and mix now. I don't trust them.


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