Holes in pistons

[pete130]

Hi all well I'm just after some thoughts , i have a 132cc stroker aerox has very high compression and I'm burning holes in pistons well there not even old enough to see burns Mark's.  So I'm thinking detanation as piston shows that, I was using octain booster but I now think that's a joke , I like the way the motor runs when it's not blowing up lol ,got to laugh my own fault cant blame the tools on this one, any way I worked out it's got some were around 15.something to 1 comp so would every one say race fuel only to keep that way, been thinking of shining the head .2 made .3 and lower squarish to help with compression kit out of box had 14:1 and I ended up taking 2mm off bottom of barbell for stroker crank. So is it either I run on race fuel or lower comp for 98 to tell u the truth I'm thinking it may run even better with so high comp I'm thinking it's to much unless I get very good pipe and would having a 25mm pipe on a 28mm exuarst out let be helping it go through pistons lol starting to think I'm answering my own questions but what's your thought I dont mine running on full race fuel lol 

[pete130]

Hoping this piston will last longer lol

[Rune 75]

Your sparkplug must be way too hot. What number is it?

[harleyracer59]

I agree you need a way cooler plug. what are the # on the current plug?

[repherence2]

Add another head gasket to lower compression psi?

I've burned a hole in a 52mm piston because i used a 47mm NCY squish band head. That was a learning lesson.

[ryan_ott]

Squish correct, correct plug heat range, engine leak tested and passed, jetting correct... if all looks good you may have a bad CDI causing incorrect timing, some stuff to consider...

[190mech]

Right on to all of the above answers,also if the stinger or silencer ID is too small excess heat will remain in the cylinder..Lean part throttle jetting due to pipe dynamics will smoke a piston during cruise also..

[pete130]

I think all are right I'm using a standard plug think is a 8 but I was allways worried about pipe made for 100cc so stinger is to small think I need 21-22mm and have wat to small i waiting on a set of .2 .3 .4 .6 head gaskets and new piston to arrive should be next week i know compression is to high but only wanted to lower to stop damage dont think i feel any loss in power but didnt think about plug temp kit in standard out of box runs 14:1 compression think I'll go back to that dont need 220psi on a street scooter nice to say it lol race fuel is another thing to help but at $160 for 20l bit expencive lol thanks all for in put my friend wants me to go back to standard crank lol but i have 2 kits now and 2 bikes to use on think I'll do a daily ride and a weekend racer like to have both lol I'm pulling motor down tomorrow I'll post some pic of this piston lol bet it's the same

[ThaiGyro]

so much to ponder here, but ryan and 190mech have the good questions. High compression...ok. How you are tuning for it looks not ok.
For me, ignition is always key...often a leading failure. On TZ multi's we had many iggy setups.

On my 50cc engine currently, I use exhaust restrictors to aid in tuning. An orifice insert in the stinger base. You cannot buy them, you must make them. (190mech idea, I think) My good engine started with an 18mm ID insert. I make ones, therefore at 17.75/18/18.25/18.5...etc. When you make a pressure wave change, you can adjust for it.

If you can "model" your change, you can get an idea of what might be needed.

When we began using center bleed pipes in my young racing days, we blew up less, then with conventional exits. When we did hole a piston, we usually knew why. Upping compression in a 2T has the greatest overall effects. More heat, pressure and return wave.  We usually had to modify everything, including crank case geometry. At the point you begin to struggle with carb tuning...back up and look at everything.

Kind of like hunting...better to sneak up on your game and take it's picture, than it is to use a machine gun and splatter good meat. Maybe you can retrace your tuning steps and figure out a solution. Or...learn the Burt Munro techniques.

[oldgeek]

Looking closely at your 1st picture, it shows the combustion chamber in the head was not centered on the cylinder. That can cause some issues as well.