I am mechanically inclined, and have a Polaris service manual for my 2012 400HO, wonder if teardown and rebuild is something I could do myself?

Want to upgrade it a little...

Welcome to 4 Stroke Tech, Inc.

Will only need to get the jug bored out, and add a BST40 with a 175 main jet, and all set.

 

If you're talking about a big bore kit,they usually come with a new cylinder and piston,etc.You have the same rod stroke as the 500 engine(75mm) but bore size is smaller. 87.9 mm versus 92 mm.Manual calls for max .020 over stock bore (50mm) but aftermarket oversize pistons are available past that. Wiseco has them for the 500 but not the 400 even though it's 455c versus the 499cc for the 500. On the big bore kits to get to 600ccs most times the original cylinder sleeve has to be pressed out,the bare aluminum cylinder bored out and the top of the cylinder chamfered to accept the larger pressed in sleeve and piston. To try to do this with a stock cast iron liner would leave it paper thin if you could even do it.Wouldn't hold up.You can go with a big bore kit or you can look at other alternatives also if looking for more power.Aaen Performance - Polaris ATV Four Stroke - ATV Accessories

 

Thanks OPT. Would have have suggestions on Cams, head work, and piston. I am not to much a fan of loud exhaust pipes. I have a company in mind for a muffler upgrade though.

 

Several different places online that have performance cams,etc including this one. Hot Cams Products, Inc. Plus you can give this forum member Rick Ritter a shout.http://www.google.com/url?sa=t&rct=j...75097201,d.aWw

 

Is a 95 mm piston going to require major cylinder work?

 

You can't bore to that limit on the 400. If you could the sleeve would be paper thin and wouldn't hold up. Yes you'd need cylinder work/new sleeve.You're talking about jumping over 7mm up from stock 87.9 mm bore. In good old American terms that's over a quarter of an inch bigger bore. If you're really looking for more power,might be time to trade up to a larger machine than by making a good reliable machine less reliable. Just my

 

Thanks OPT! After I get my new rubber, will add a Dalton clutch kit, and see how that goes. Are aftermarket cams worth while? Or too much expense for little gain.

 

Just my again on this. Higher lift/longer duration cams will be screaming for more air and fuel, calling for jetting changes,less restrictive air filter,then the exhaust will be screaming to relieve itself from all the extra load on it,etc.In other words hard to do just a cam without addressing other items also. The clutch kit and a good less restrictive exhaust system designed for your model should help. Plus many times rejetting isn't necessary on aftermarket exhausts. Depends on the mfgs requirement and how your engine runs and how the spark plug looks whether it's running lean or not.

 

Thanks OPT. Gonna add an MBRP muffler after I do my clutch, re carb work needed.. This will all fit the bill nicely.

I have 2,800 miles on it, plane on 10,000 before I get rid of it.