Worn piston/sleeve? (pics included)

[KillerWabbit]

The car: RS4-3 SS
The engine: 12R SS with only 1.5 gallons through it
The question: Could my piston/sleeve be worn out already?

First off, my break in... I think I might have broken it in for too long. I idled 4 or 5 tanks, then put around another 5 or so while starting to lean out a little. I didn't hit WOT til the 10th or 11th tank.

The engine has good compression when it's cold, as far as I can feel with the pullstarter. The car runs pretty good for the first tank or so, hitting second gear easily without hesitating. It scoots along nicely. Then, once the engine gets up to temp and a couple tanks later, it just gets slow. It will not hit 2nd gear anymore, unless I adjust it lower, but then it hits 2nd and doesn't have the power to accelerate. It has been doing this the last few weeks, about 1/3 gallon worth of fuel I'd say, everytime I go out running it. I run the engine in the 270s, with front and rear windshield holes and the side window cut out. Once the engine starts to suck and lose power, even in first gear, you can tell that it just doesn't rev near as high as it used to. I even held the wheels off the ground and gave it WOT, which I know isn't the best thing to do, but it wouldn't even hit 2nd with no load. Also, I can feel less compression when the motor is hot. I know the problem isn't anything to do with it shifting because even in first, it just doesn't have power and sounds like it's revving like 15-20k, maybe.

Here is the piston and sleeve. This is as far as I could push the piston before it gets stuck...

Is this piston wear normal?

The sleeve shows hardly any signs of wear at all, while the piston is kinda scuffed. I thought the sleeves wore more than the pistons.

Here's what I think might be happening. Because I broke the motor in too much, it wore the piston a lot because the sleeve never got up to temp and expanded. So now when its up to temp and expanded, there's less compression. I was pretty sure this was the problem, but after seeing that I couldn't push the piston very high in the sleeve, I'm not very sure.

This is my first nitro engine, so it's a learning experience. What do y'all think?

 

[newnitrofan]

Killer I am not too sure you can idle an engine too long during break in. Also if you can't push the piston through sleeve most chances are the engine is still great. You should look for other issues such as air leaks in your fuel tank or fuel tank system. Look at other issues homie. Make sure your engine is sealed well backplate and all.

 

[KillerWabbit]

I thought I broke it in too long because my thinking was that the longer you break it in, the longer it stays at low temps, and the more you'll just wear out the piston before the engine sees higher temps, allowing the sleeve to expand.

I have already sealed the backplate and the carb a week or two ago and it still runs like crap. I was kinda hoping the piston would push right out the top so I could certain of the problem and just get another sleeve/piston. But, I'm not sure what it is now. I haven't checked the fuel tank yet, so I'll see about that. I'll probably take the primer out and seal that up. I figured it was the sleeve because the car runs fine whens it's cold, but once it's hot, it SUCKS.

 

[Nitroz28]

looks like u need just a new piston those scuffs can't be good but u can't push it up all they way thats good it lookes same way and i only got 1/2 gallon on mine , but i sucked in dust and killed mine in 5 min,s did u get dirt into motor i sall bubbles when ill turn over my mill see if urs do to and if it has no compersion then its done goodluck:thumbup:

 

[Waste Land]

I agree with NNF. Engines don idle real good when they run really rich like they do in break ins. Tight sleeve plus alot of gas is gonna cause some idling troubles.