my 400 xplorer has 2000 miles on it and runs very strong .it runs as good now as when new!!it is all stock .ive read posts on here where the polaris piston would break and fall down in the motor.i would hate to tear down my engine to put in a wiseco but i would rather change just a piston rather than risk doing a whole bottom end..ive used polaris synthetic two stroke oil from day one also.should i change to a wiseco or not even worry about it??another question...could i just pull my cylinder off and change the piston and put the jug back on with out honing or anything and it last as good as stock??whats the best thing for me to do on theis polaris??calling all gurus!!!!!!

 

boneylong,

If you are going to seriously modify the engine (i.e. port job, highter compression head, top end pipe) then a Wiseco is a must. Making an engine rev past 7000 rpms is a sure way to kill a stock piston. However if you are going to leave the motor mostly stock, the stock piston will do. Here is a little known fact, Wiseco pistons being MUCH softer are actually more prone to scuffing and cold seizures than the stock cast piston. There is a way to make it more scuff/seizure resistant. You could go with a Swaintech coated piston.

Hope this helps!

 

Once you have more than a few hours/miles on it, I would strongly recommend that you have the cylinder honed to true it up before you put in a new piston. To me it seems like a fairly cheap investment, as the new piston alone is about $100, plus gaskets, new piston pin, and wrist pin bearing. More like $150 (or more) before you are done. Ritter Cycle charged me only $35 to hone the cylinder to match the piston, fairly cheap if you ask me, considering how much you are spending, and it really will help improve engine life/durability. Rick even sent me out a cylinder he already had bored, along with a matching piston, and I sent him back my cylinder after I did the work. This way I didn't have to wait until my cylinder came back to put it together. Just so you know, Rick charges you for the whole cylinder, than after he gets yours back, he checks it out, and if it is OK, he will credit you back all but $35 of what he charges. I think he does this to be sure he gets yours back on a timely basis.
Compared to the stock piston, the Wiseco is slower to 'break in', and is actually touchier about warming up before you give it too much gas (cold sieze) than stock. On the plus side, it is tougher, and MUCH less prone to cracking a piece of skirt down into the engine than the stocker.

For the record, My Xplorer went 5200 miles before I changed the piston, and if memory serves me right, had about .010 clearance between it & the bore. For comparison, Rick set up my Wiseco with .003 clearance. In my opinion, mine was just starting to get a little 'knick, knick, knick' in the engine (at idle), which it doesn't have anymore.

 

boneylong,

I have a '98 Xplorer, and the only mods I did to it was a K&N air filter, boysen pro reeds, and a stiffer clutch spring to help lighten the front end on takeoffs. I've put 7200+ miles on that machine and have not touched the engine or transmission. Like everyone else says, it is a strong engine and only needs the weisco boost when you add mods. If you ever worry about it, just get the compression checked every once in a while. But if it happens to blow...no big deal. If anything, you get to bore it 20 over, put in your weisco, and be able to pump a few more ponies from your xplorer. It's good to take some preventitive measures, but if it's not broke, don't fix it!!

-------
00 Scrambler 400 4x4 K&N air filter
98 Xplorer 400 K&N air filter, pro reeds, clutch spring

 

This may be the exception rather than the rule, but I have seen a machine with a little under 8000 miles, break off a piece of the piston skirt, send it flying through the engine, cracking the crankcase, and bending the crankshaft. Repair estimate was $1000. I know that it is rare to do that much damage, but I have a low threshold for repair costs. I compared that to the $200 it took for the Wiseco (piston, gaskets, etc.) and figured it was money well spent. I would have to add, though, the engine that had this happen didn't just let loose with no warning, it was slapping that piston around enough that SOMETHING had to give. Just that it's owner was one of those guys who says he will have it looked into 'someday' but never got around to it until it was too late.

 

I had my stock polaris piston skirt break off and send it through the top of my crankcase. I had a little over 40 hours on the machine at the time. After buying a new wiseco piston and new crankcase, I remove the cylinder every 10 hours just to check the rings and piston for wear. So far so good after another 20 hours. Stock polaris pistons do fail, believe me it's much cheaper to just buy wiseco than it is to buy a new crankcase.

 

so should i tear old satan down and install the wiseco???

 

Yes, if it was me I would definitely do it. It will be much cheaper for you in the long run. It costs me 25 bucks at my local machine shop to get my cylinder bored and honed to fit my piston. The wiseco will cost you about 80 bucks for the piston and rings. Also you'll need a new base gasket and head gasket for about 20 bucks. A 120 bucks is a small price to pay now compared to 300 for a new crankcase. It's kinda like having a good insurance policy.

 

MGM,

Was your piston failure after adding the pipe and other mods, or was it with everything stock? I can't recall reading about a stock piston failure with so few hours on a machine that was kept stock.

Waylan

 

I'm sorry, I forgot to mention it was not stock at the time. At that time it had the head decked, hpd pipe, v-force reeds, and 39mm kehihn carb. I should have replaced my piston when i had the chance. I had it ported and polished when i installed the wiseco piston and still haven't had a problem yet with the exception of other things breaking not engine related. Also I had sunk my bike 5 or 6 times before that when i was trying to install the right snorkle. So that couldn't have been good on it.