My Scambler died on the first run last weekend. I took off the head and it looked like it was shot by a shotgun, very bad around the edges. I did find a small pice of metal (not aluminum) stuck to the head. The top of the piston looks the same as the head; peppered. I haven't taken off the cylinder yet so I don't know if it (the metal) is part of the rings or not. My question is, if there was metal in the cylinder, could it also be down in the crank? Do I need to pull the crank and have it inspected. Rick at Ritter is sending me a new top-end, I don't want to risk it happening again if there is more loose metal in the crank area, or if the crank is damaged. I have never taken out a crank. Anyone have some thoughts on this?

 

sounds like it could have been part of a ring that broke off and banged around in the compustion chamber for a while. Once you get the cylinder pulled off, you can see down into the crankcase. Drain any excess oil in the crankcase. If you see any metal pieces down there, you should probably split the cases to get it cleaned thoroughly. Some guys have simply flushed the crankcase with diesel fuel and had good luck, while others have not. If you don't want to spit the cases and simply flush things out, it comes down to the question, "Do you feel lucky?"

I just split my cases and it was not difficult at all. If you have a steering wheel or gear puller, that makes it very easy.

 

A peppered crown is a sign of detonation, BUT......since you have located a piece of metal you definitely need to find the cause. Things to look for would be either a piece of ring (not very common), part of the top end bearing, a piece of the lower rod bearing or thrust washer, or even something crazy like a piece of the iron liner from the cylinder itself. While you have the top end off inspect the rod lower end very good and check for any up and down play. Polaris 400 cranks are very tough and the rods hold up to unbelievable stress. When my old bike cracked the cases it ran wide open for about 3min until it ran out of fuel. Nothing would kill it otherwise. The crank was put back into the new cases and Handycap still rides it today. Hope you find something though. It's bad to look everything over, not find a single thing, and have to put it back together.

 

check compression psi and counter balance.

 

our 400 explorer had similar thing happen it just kinda locked up one day tore it down and found part of the thin crank roller bearing what i mean is the cage that holds the ***** in place had came apart and the pieces of the cage was everywhere the ***** where still in the brng though it tore up cylinder and piston pert bad bored it installed new brngs make sure you clean out debris from bottom end if thats wht happened

 

My 2 cents

A sound like this was your maiden voyage with this machine, and it’s a new big bore kit.

So I would first take the piece of metal you found and get a magnifying glass and carefully examine it. You should be able to see if it is flat or square shaped or if it’s round and elongated.

If it’s more flat than I would say its part of a ring and since it’s a new cylinder bore you may not have dressed the ports properly and hooked a ring, or your end gap was to tight or your piston to wall was not correct.

Now if the piece is round and elongated then it’s probably a wrist pin needle bearing that either failed from detonation or a improper wrist pin fit.

Next it could be the circle clip that holds the wrist pin in place not seated properly when installed .

AND THE LIST GOES ON

So now get your butt out there and take five minutes and pull the jug off and end all this speculation!!!!

 

A rivet out of a main bearing cage will do that type of damage .

Rick Ritter

 

Everyone,
Thanks for all the help I'm learning alot here! Actually, it wasn't the first ride after rebuild, we have had the bike for about a year and love it. I hope to get the cylinder off soon, my day job gets in the way though! I will post as soon as I find out where the metal piece came from.

 

piston ring pin,check for this,it happen on my xcr last year and hapened to be a piston ring pin not good enough sealed,so there was always a bug on the jug at 3/4 to wot response,heard a guys just exploded his xcr for that same situation not much long ago on amsnow site forums,,

 

Ok, I got the cylinder off, the intake side of the piston and cylinder are very scored, in fact the rings on that side are almost gone its like there was no lubrication there and got hot. Also, there is about a 1/16 inch of play in the piston rod where it attaches to the crank. Could the crank have gone bad and therefore the piston was moving incorrectly?