I just acquired a 2003 Polaris trailblazer 400. It would start after a lot of effort. Then it would die after about 10 minutes. I checked compression and was getting almost 70 lbs. I pulled the head and both rings were broken. One was in 3 pieces, the other was in 2. I have ordered a new piston after having machine shop look at cylinder. I was told it needed to be bored 25 over. The oversized piston and rings are now at the machine shop with the cylinder. My question is what else should I do? I keep hearing about crank seals. Should they be replaced? Anything else I should replace? What's the best way to check the automatic oiler? The bike itself is in mint condition. I plan on using it for years to come. I want to get out and enjoy the trails. Any help is greatly appreciated.

 

Yes I'd replace the crank seals or at least the one that gives the most trouble on the 400 which is the one behind the drive clutch. To get to the other crank seal you have to pull the recoil,flywheel,stator,third engine case,water pump to even get to it.Item #24 on the parts break down. Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse If there is ANY up and down movement on the rod(side to side play is ok) then the cases have to be split and a rod kit installed along with crank bearings.Oil pump is the one "iffy" thing on the 400 as it's located at the front and subject to water and corrosion and freezing up. Pull the front cover plate and inspect its operation by pressing the throttle. You can if you wish just bypass the pump,block off the oil injector going into the intake manifold and premix 40/1 if you have any doubts. Just depends if it's been in a lot a of water over the years or if the pump is rusted. One other thing that a lot of people over look is bleeding the 10 mm bolt on top of the head to remove any trapped air from the coolant. Failing to do so can cause an engine to overheat possibly damaging that new top end along with warping heads and cylinders. Not a big fan of just doing top ends as all it takes is a lower rod bearing to spit pieces up and can take out a new top end.Something you take a chance on with just a top end rebuild.

 

Can all this be done without removing the engine? I don't want to half *** this?

 

To do it right then yes the engine has to be removed from the frame. If the rod and crank bearings are replaced you also have the water pump to rebuild. There are 2 seals,each goes a different way and a water pump bearing that have to be replaced and the small hole in the w/p housing must not be blocked. Here's a good cheap 5 buck manual that explains all of this and can pay for itself many times over on service and repairs. 2003 Polaris Trail Blazer 400 Service Manual PDF Download

 

Thanks, downloading now

 

Well...not that OPT's advice isn't sound, I've personally have had three of these and never had a crank seal go on them. I think I'd be more concerned with any of those ring parts having made it's way into the bottom end...personally, just because they were broken, I'd split the cases...piece of mind thing for me...and yes that would require removal from the frame...

 

I am mechanically inclined. I do work on my own cars and a little tractor I have. How difficult it is to split the case halves? Can the whole process be done in a weekend?

 

Not that hard. Yes you can have it taken apart in a short time. Takes a little just to get it out of the frame. From there it's fairly straight forward. When you get to the water pump and counter balancer is where it takes time. Be sure to inspect the balancer main bearing. If coolant has gotten into the counter balancer cavity it can cause problems over time. Couple online places that can repair counter balancers if needed.Just look at the manual and it gives you some step by step instructions. Again worth the price rather than going at one blind. There is a special tool if the counter balance needs to be pulled. Some have made their own,others have bought the tool.http://www.rvservicetools.com/online...&category_id=8

 

If I am splitting the case halves, should I go ahead and replace bearings, seals gaskets? Do a complete bottom end rebuild? It seems silly to do all that work and not replace all the bearings?

 

Absolutely! All bearings and seals,plus have the rod checked out and replace with a new rod kit. Not a worse feeling than to go this far and have something fail and it could have been replaced. Most machine shops will press the new rod on and true the crank shaft and shouldn't charge much. Here's a complete bottom end kit.New Polaris 400 400L 93 03 Sport Complete Engine Bearings Gasket Rod Rebuild Kit | eBay