Keep breaking rings post install BB kit

[DavidBrown1212]

I got the 85CC BB (Dolmar/Makita 6400) kit from weedeater man, and while I am no 2-stroke tech, I am a pretty handy (I can rebuild a Cummins or build a structure) so I thought after my local saw shop quoted me well over a bill, I would try it myself. Does not seem to be a big deal, watched a few You-tubes on the subject and felt pretty comfortable with it. Well, a couple of beers and videos later, I decided to do a mild port. More of a polish, really. Anyhow, I did not remove much, the intake port looks a little sophomoric, but an improvement, the exhaust port came out really pretty, but then I decided to attack my transfer port. My burr bit had no buisiness in there, I knicked the wall, and raised one side 2.2mm at the peak (it was parabolic in shape). So when I go to install it, I have some trouble getting the jug on, but I eventually get it.

So when I finish, I got no compression. I check the spark plug, I check the decomp valve, then I tear it apart to find my ring in pieces. So I do it again the next week, same result. Could this be my sloppy grinding, or am I being too forceful putting the jug on?

There is only one ring per piston, sand the transfers in with 220 grit (what grit?), can I get any 54mm rings? I have seen some incredibly sloppy/extreme porting where I thought rings would surely catch! Why my mild shaving?

I will post pics shortly, time to work!

 

[XSKIER]

Yep. We need pics!

 

[nmurph]

Without pics, it's just a guess, but I would bet that you are snagging a ring on the I/E. You need to bevel the edges of those ports. And the flatter you make them, the more bevel you need to give them.

2mm of additional tranfer is a lot. Did you put a degree wheel on the saw?

 

[DavidBrown1212]

Some pixs

 

[pioneerguy600]

When you are sliding the cylinder down over the piston the ring ends can pop out into the intake port, it needs to be gently pushed back into the ring land, a popsicle stick, or coffee stir stick worked through the intake port opening will do a good job of tucking the ring back in til the top of the intake port covers the ring ends.

 

[watsonr]

Pictures don't work. Are you using a ring install tool to squeeze the rings tight to the piston as you slide it in?

 

[Tractorsaw1]

Well, a couple of beers and videos later, I decided to do a mild port

Don't think degree wheel is in the picture here

 

[DavidBrown1212]

No, and I did not do anything to change the timing. I did not enlarge the intake or exhaust ports. I did use a ring compressor.

 

[griffonks]

When you are sliding the cylinder down over the piston the ring ends can pop out into the intake port, it needs to be gently pushed back into the ring land, a popsicle stick, or coffee stir stick worked through the intake port opening will do a good job of tucking the ring back in til the top of the intake port covers the ring ends.

This could be where the rings are breaking.

 

[samhop]

not that i know anything but you might get better input if you post closeup pics of your porting work and the rings showing where the ring broke and explaining where the pieces ended up.
when i put a P&C back together I pull the pin on the piston give it a light lube with some mix and slide it in easy feeling for any hangs. then pull the piston and give it a good looking over you should be able to see if it hung at all even if you did not feel it. look for marks or metal on the edge of the ring or scratching on the inside of the cyl.
good luck