Why does this keep happening!!!

[thegoldensb]

Okay i bought an 87 spree got it took it apart piston and cylinder was gashed so time to rebuild.

Bought one of taaz 48mm big bore kits and it continues to blow up this is now the 3rd kit with not even 20 miles on it everyone blew up with same gash.

Both cir clips are installed correctly and were in place everytime upon removal.

I honestly dont understand what is going on with it i thought it could be loose metal floating around the inside but i completely took it apart and found nothing just to put it back together and still blow up.

I was premixing with the pump still attached so i didnt figure it to be running dry.


ANYONE HAVE ANY IDEAS LET ME KNOW THIS IS GETTING RIDICULOUS!! MAYBE HOW TO DO A GOOD CRANKCASE FLUSH!!

[Mystic]

maybe need a new crankshaft, crank bearings or connecting rod bearing?

[thegoldensb]

Good input but I'm struggling to find parts for it being it's so old

[evilone]

MAYBE HOW TO DO A GOOD CRANKCASE FLUSH!!

fill crankcase with gas and tip motor upside down a few times.

[kingkamehameha]

You could have bought a dio motor with all the money you wasted on 3 bore kits

[thegoldensb]

I know right. Wheres the best place to find dio motors just check local stuff?

[Bear45-70]

The top ring was installed wrong and that's why you screwed your piston.

[thegoldensb]

How was it installed wrong how should it have been installed

[Bear45-70]

How was it installed wrong how should it have been installed

The rings have to be right side up and the ring ends have to line up with the pins in the ring lands. In your pic the ring end is off to the right of the pin. Otherwise, basic 2 stroke mechanics.

[thegoldensb]

I did line them up in the ring lands to the ring pins but basically i installed them completely upside down?

[mousewheels]

I cannot see the lower ring, but upper looks installed ok, the chamfers need to mate up with the offset pin in the piston - and do...

In your first post you said this is happening the the same spot. Have you been putting replacement pistons into the same bore? Could it be there's a nugget of piston still on the bore?

pistonDamage_1.jpg (56.64 KiB) Viewed 5171 times

[thegoldensb]

I have bought new kits and used the new piston and bore each time. Both piston rings were installed the same way.

[thegoldensb]

It almost looks like the ports on the side aren't cut the best and has metal bits pertruding out slightly and could be catching the rings. Does that sound possible?

[Bear45-70]

You see the piece of ring that is missing? That is what grooved your piston and bore. Not the port or anything else. The ring broke and a piece of is tore up your piston and bore. This ain't rocket science.

[swimmingfree]

have you ever look at what the ring end gap was before you put it together ??? im wonder if when they get some heat on the rings that's why they get hung up in the ports ..
it also could be that the ports need to be chanfer more ..