Piston ring installation

[jschief]

I was trying to get the piston back in the liner and broke my new piston ring :arggg: . Is there a trick to doing this? Nothing seemed to work when trying to get the piston back in the sleave and engine.

There is a little pin on the piston and I am sure I lined the ring opening with this pin, but the ring might of slipped. Any help would be appreciated. I have time until a new piston ring gets hear. I can not wait to buy another heli, I really hate this down time :bomb: .

[flyinfool]

As you mentioned you have to be sure that the ring gap is lined up with the tiny pin in the piston groove and be sure that the piston is going in the right way (radius notch in bottom of piston skirt goes toward the carb).

I normally start with the piston at top dead center while I push the cylinder liner in.
Do not twist the liner to get it started as this will turn the ring.
Once the liner is started into the block and the piston is started into the liner you can then safely turn the liner a little if necessary to line up the indexing pin for the liner.
Try not to let the piston ring move up to the ports in case the liner is not lined up exactly yet, if the ring gap gets into a port it could catch and break.

This was a lot harder and took longer to type than it is to do.

[BarracudaHockey]

Aside from lining it up properly a little light assembly oil or atf helps things along nicely.

[jschief]

Thanxs for the info. I thought everything was fine when I put the ring on the piston with no hassle. I was afraid of breaking the ring when putting it on the piston I did not think I would have trouble installing it in the liner. The ring is so fragile.

Another question is since I have to wait for parts is it smart to order and change the bearings I heard the OS bearings do not last long. I have about 5 gallons thru the motor. I do not do 3D yet so the motor doesn't see alot of stress.

[jschief]

FYI. For those other somewhat newbees like me. When it comes to rebuilding the motor, the 2 stroke motors have a ring alignment pin on the piston. The piston ring gap opening needs to fit over this pin. Doing this the piston and ring fit in the sleeve pretty easy. Just a tip so you do not break the ring like I did putting the engine back together.

[flyinfool]

Your right, the OS bearings do not last long.
I have been having very good life from the stainless steel bearings from RC-bearings.com.

With only 5 gallons thru the engine why did you need to take it apart?
If you were replacing piston and ring due to a lean run I would also consider the main bearing suspect. If not then go by how the bearing looks and feels.
With the crank out, flush the bearing with a solvent and using the tip of your finger to feel for any roughness. Of course if there is a lot of rust on the bearing, that is not good either. Be sure to re-oil the bearing immediately after checking or it will rust fast.

[jschief]

I ran into a lean condition and the piston did not have a hole in it but it was starting to form.

With only 5 gallons thru the engine why did you need to take it apart?
If you were replacing piston and ring due to a lean run I would also consider the main bearing suspect. If not then go by how the bearing looks and feels.

I am only hovering around and some forward flight so I think the bearings are o.k.
I just put everything back together and ran 3 tanks thru it and everything is running ok.