I have a 99 polaris 400 sport. I replace the piston which had a hole in the top, right under the spark plug. I had the cyclinder honed out to .10 over and replaced the the piston. It ran for about 20 minutes no problems, took it around
the block, the temp light came on and when i took it apart the piston was burnt in the same spot.
I'm running the stock plug
i bleed the oil injection

My question is
Is there anything else i should have done
Timing
Carb adjustments
Thanks
tutiii

 

running way lean

what you mean by "i bleed the oil injection".................is you pump working? sounds like it's not

 

if you have hole burnt in the piston under the plug its burning way too hot and or not getting enough gas or too much air.

 

In the manual it says to bleed the oil injection.

Burning way too hot meaning there is not enough oil in the gas?

To adjust the air, there is a screw on the carb exhaust pipe side to adjust correct?

I had the that in and backed it out about 1 to 1.5 turns?

thanks for the replies
tutiii

 

The screw you're talking about only affects the idle to 1/8 throttle mixture. If you're burning up pistons, the midrange & topend jetting WAY lean. Is there a pipe on it?? If you bled the injection system that should be OK, but was it smoking?? Could you smell the burning oil??

Now, if the temp light is coming on that sounds like a whole other problem. Are you low on coolant?? If not, radiator plugged?? If not, probably the water pump isn't working properly.

 

When i first let it run i added some oil to the fuel. there was plenty of smoke.

There is a stock pipe on. this quad is all stock.

how do i adjust the midrange and topend?

when the light came on the overflow reservoir was full and boiling.

i afraid after i put in the second new piston this will happen again.

i'm thinking about rebuilding it and taking it to the dealer, but i had plans on
selling this quad and don't want to spent a ton of money on it. but can sell it the way it is.

thanks again for your help

 

To richen the midrange you raise the needle by putting the retaining clip in a lower position. The topend is changed by richening the main jet.

Boiling water/coolant......... sounds as though it's circulating, but like the radiator is clogged or alot of fins are bent.

Where do you live. I'm actually looking for a 400 possibly??

 

this quad has very few hours, when it first blew the piston it was in February and it was snowing. before that ran fine.

i never touch a thing, this is the part that is confusing me.

i live in PA, outside of Philly (Lower bucks).

i had this quad since 03, most of the riding is in the snow and it doesn't snow too often

 

If you were running it in the winter, the jetting was too lean for the cold temps & blamo...... blown 2-smoker. Just how cold was it out when it let go?? 2-strokes need to be jetted for the outside air temps.

Temp ranges are generally as follows...... 0*-30*F 30-50*F & 60-80* & 80*+ This is a VERY ballpark estimate. Humidity also factors in. Factory jetting is usually good for a wide temp swing, but, what's good at 70* will for sure be too lean at 20-30*.

 

it was in the 30's.

but yesterday when the 2nd piston had a problem it was mid 60's.

where should the needle be from the factory?