I would look somewhere for an air leak,like the carb boot.The oil pump is gear driven and very rarely fail.Also look at the cases to make sure you don't have a crack in them.Like the one in my pic's.Let us know if you find something.

 

better safe then sorry i, would just premix from now on, and dont worry about that happening cus i think its happened to every polaris 400 scrammy/sport owner.

 

It was more than likely lean at part throttle. The 34vm carbs that come on the 400's have a lean middle to them. If you didnt have an air leak then the atmospheric conditions must have been good and caused you to run a little lean and it will hole a piston.

 

Looking at all of these posts, I think I missed the most likely cause and I think CED found it. A lost plug, a blown gasket or a torn boot has caused more than one 2 stroke to burn up.
This just happened to a buddies race car about a month ago, so I should have remembered. A plug came out of the intake manifold. The header, from the head all the way to the exhaust tip turned bright red, even at idle!!!!!!!!!! If it would have happened racing that engine would have been done.
Look for leaks along the whole intake tract. Good call CED.

 

thanks guys, i will inspect the air intake and inspect for any case cracks today and get back to you all. im really glad to have the support system this forum allows us all to use!!!!!!

 

WELL IVE INSPECTED THE ENTIRE AIR INTAKE TO THE CASE AND CYLINDER AND FOUND NO CRACKS IN ANYTHING. MY BEST GUESS IS DUE TO THE FACT I HAVE MADE SOME AIR MODS, NEW K&N , NEW HPD SILENCER THAT WHEN I WAS RUNNING IN MID RANGE DRIVEN ACCROSS THE DUNES THAT IT JUST LEANED OUT. I THINK THE BEST THING TO DO IS REPLACE PISTON, RINGS, WRIST PIN AND BEARINGS, PUT IT BACK TOGETHER AND I WILL CHANGE THE MAIN JET 10-20 HIGHER THEN CURRENT AND ADJUST THE CLIP ON NEEDLE DOWN ONE SPOT, FIRE IT UP REV IT FULL ,SHUT IT DOWN CHECK THE PLUG AND LOOK FOR BROWN COLOR IN THE PLUG. DOES THIS SOUND LIKE THE RIGHT THING TO DO????????[img]i/expressions/face-icon-small-smile.gif[/img][img]i/expressions/face-icon-small-wink.gif[/img][img]i/expressions/face-icon-small-sad.gif[/img][img]i/expressions/face-icon-small-blush.gif[/img][img]i/expressions/face-icon-small-disgusted.gif[/img][img]i/expressions/face-icon-small-happy.gif[/img][img]i/expressions/face-icon-small-mad.gif[/img][img]i/expressions/face-icon-small-shocked.gif[/img][img]i/expressions/face-icon-small-tongue.gif[/img][img]i/expressions/face-icon-small-cool.gif[/img][img]i/expressions/face-icon-small-frown.gif[/img]

 

The K&N filter in place without jetting it is cause for trouble. I had a Kawasaki 400 tripple(motorcycle) that was too lean due to K&N's and had to make some jet changes. I also had an expansion chamber on it which didn't help either. Mine never burnt a hole but broke the piston skirt and whiped out the rod bearing, plus cracked a ring. The tinny sound is what mine made too and I was told the rings make this sound when it is running too lean and just about to let go.

 

SO WITH ALL THIS IN PLACE AND SAID DOES ANYONE KNOW THE BEST PLACES TO GET PARTS?

 

http://www.partsland.com/ will give you an idea on cost, if buying from a dealer. Plus the part numbers, are listed.

 

What up dude! Hey, I've done that to my Scrambler 3 times!!!!

Let me start from the beginning: First of all, get rid of your factory oil injection! These injectors are mechanical and are subject to wear. Once they wear a little bit your fuel to oil ratio go's out of whack(normally unknown to the rider). HPD makes a kit for next to nothing that eliminates the injector. I highly recommend it!

Second: What octane fuel are you running and at what elevation?? Are you factory jetting?? Did you buy it from a Polaris dealer?? Did they jet to your elevation?? Using to low of octane fuel can result in pre-detonation. This condition can do all sorts of nasty things to your quad (blowing holes in your piston, blowing the spark plug out of the head... I've done that and it sucks!).

Third: If you ride in any really dirty (dust or sand) terrain, it is a good idea to clean your carb every 2nd or 3rd ride. It only takes about 15 min. and is well worth it. A piece of sand or debris in any part of your carb can affect ratio. When you are reading your plugs, try and keep them a chocolate brown or a little on the grey side. You always want a little brown color to them though. Also, take your clutches apart twice a season and clean them with carb cleaner. They collect quite a bit of dust(belt dust and dirt), and that lessens the grab on the belt(power loss, engine revs differently). Also burning your belt up quicker.

All of you guys planning on modding your Scrammy's KEEP YOUR CLUTCH PLATES CLEAN!!

I've had my '98 since about Feb. '99 and have got it pushing just about 75 horsepower at the crank. These are my mods:
60 thousandths bore over (burned it up a couple of times!)
Wiseco forged piston
HPD billet head and girdle kit with 15:1 dome
CPI Custom drag pipe and silencer
Aein Roller clutch
39 PWK D-slide carb with reworked internals (came off a '01 RMK 700)
I taken about 55-60 pounds off it


I hope that helps a little.

OLE