kjac3585

Piston stuck on middle ring inside cylinder after trying to re-install it.

Pictures:

http://i.imgur.com/4Yhey.jpg

http://i.imgur.com/ZLaGf.jpg

I'm new to engine repair and this is just a cheap lawn mower I am trying to rebuild.

I've taken the piston out of the cylinder to check everything. I used a hose clamp around the 3 rings to compress them and it slide right back in no problem. I then realized that I hadn't aligned the gaps in the piston rings properly and had to take it back out again to fix that. I tried to install it the same way and some how got stuck on the middle ring.

I couldn't push it in or out but it would spin freely. I then tried tapping on it with a rubber mallet to see if it would move in or out. I didn't budge, but now it is completely stuck...it won't even spin inside the cylinder.

It's an aluminum block so I am afraid to damage it by being too rough...perhaps I've already damaged it now that the piston is stuck? What can I do here?

kjac3585

i got it out by gently tapping on the backside of the piston with a metal rod and hammer. I used pb blaster on it as well to help glide it along. Now... does anyone know anything about getting the timing gears right? haha... seriously though, I am stuck on that one as of now.

cheese

Generally you line up the marked teeth on the cam and crank gear. Knowing what you have would help.

kjac3585

Tecumseh LEV120-361020C

You are correct cheese. There were indicator marks on both the crank and cam shaft gears that align with each other. Keep an eye on these thread though please...I am sure I will have more questions for you.

kjac3585

ok the lawn mower is back together now... Changed out the valves, all the gaskets, rebuilt the carb, cleaned it all up. Now, it doesn't start. The spark plug is not getting wet, but there is fuel in the carb bowl. What could be the problem here? I'm almost positive the timing is correct because I lined up the gears with the appropriate marks. The valves I changed out should be correct...nothing looked problematic when I installed the new ones. Yet the spark plug is dry as a bone... I cleaned out every little holes and changed out a few of the o-rings on the carb, I can't imagine why it wouldnt work.

any ideas cheese?

cheese

How much compression does it have?

kjac3585

yea i would like to test that...just have to buy a compression tester. didn't want to drop 30-40 bucks on one but I might have to it seems. Assuming there was very low pressure..what would you suggest? thanks!

cheese

I'd probably start by checking valve lash. What were the ring gap clearances?

kjac3585

cross-section of my setup


Well, I'm not sure I have a valve lash on this setup (don't really know what this is). The ring gap clearances as in the piston rings? I'm really not sure...i didn't change those out. I suppose I could read through the repair manual and find the clearances if need be.

cheese

The manual will give you acceptable tolerances, not what the clearances of yours are. It's one of the things you check when building or reassembling an engine.

The valve lash is the clearance between the lifter and the valve. You said assuming it is low... so assuming it's low, these are the things to check.

kjac3585

ok im new to all of this so I'm just trying to figure out what you meant.

If you mean the side clearances on the piston rings I have no idea...it says I need a feeler gauge which I don't even know what that is. The compression was at least good enough to run the engine before I took it apart. So I assume the side clearances on the piston rings is adequate since nothing was changed. The valves/valve lifters on the other hand were changed.

From what I am reading about the valves it mentions re-cutting the valves or seats with a grinder to ensure a proper fit. Seems way beyond my level of experience, what equipment (besides a grinder) would one need to accomplish this? This is really going to be a pain if the valves need to be ground down. I've ordered a compression tester, should be here Monday. Thanks again

cheese

Ok, what did you change when you put the engine back together. You talked about changing the valves, which is why I mentioned it. It it ran with those rings in it, then assuming you didn't crack them when putting it together when the piston got stuck (they may have), then they should be ok. I'd check the valve clearances first though. You can grind the stem to obtain proper clearance... but just check them first so we can figure out what your problem is. This doesn't go along with assuming the compression is low, but I know where assuming gets me, so... have you checked for spark? Have you put a little fuel into the spark plug hole to see if it will start?