First vacation in years, wife and I tried the new "ride the wilds" in northern NH. Leaving the parking lot on second day, after riding 60 miles the day before, engine dies. Couldn't wrap my head around the problem so we loaded it up and took it to garage down the road to find out piston skirt broke apart. 5 hour ride home and find out this is a common problem. Pulled engine out, pulled jug off and sent it out for machine and new piston yesterday. Poking around at the lower end on the bench tonight I find a very small amount of wiggle in the pto shaft (up and down, none in and out). I am assuming there is no "acceptable" amount of play here. The rod and other bearings all look great and rotate freely. Can I/should I replace just the outside bearings and seals? Any help on what the must have seals, gaskets, bearings I will need. I recently repaired the common milky counterbalance oil issue and have a good recolection of what's in there. I am hoping to do this as cheap as possible and would love a little guidance. Thanks ahead of time.

 

Hard to go cheap on the 400 2 stroke with very much success.Almost impossible to get all the shavings from the broken piston skirt out of the lower end even if you flush it several times.Some small residue remains.If there is any play at all in the crank bearings or rod the engine needs to be split. If you do that you may as well do it right and have a new rod kit,bearings and crank seals replaced.I had to learn the hard way years ago on the 2 strokes and would never warranty just a top end only.A lot of the times it ends up being double work if you just install a new piston only,plus you take the chance of having metal shavings from the rod or crank bearings destroy the new high $ top end..

 

That's what I thought. I ordered the bearing and seal kit this morning. Looking at the manual it says I will need a special puller for the counter balancer. Is that true? Any way I can make one? How hot am I going to need to get the case? Propane torch work or hotter? I've split and repaired a chainsaw case before, this is just a little bigger adn more complicated right? By the way, thanks OPT you are just the guy I was looking for an answer from.

 

You'd have to fab up something like this that the bolt had internal threads to pull the counter balancer up. Prone torch is fine. This is all I had to use at the shop other than a hot plate for large gears and bearings.https://polaris.service-solutions.co...6&cat=1&sub=24

 

Yeah I saw that tool. I am thinking a couple nuts welded together onto the end of a large bolt will work the same as that puller. Any idea off hand what size and pitch the threads are?

 

Not off hand as I just used the tool. Once you get to the shaft you can take a metric pitch gauge and find the size or just measure the threads on the impeller nut threads.

 

I have split these cases in the past without removing the balance shaft. the bearing on the oil pump side of the balance shaft fits loose enough. the shaft wil stay in the other side. Once apart some heat help from a friend and soft hammer. and shaft will come out. reassembly heat case once it's together and the shaft will push back in pretty easy. DON'T FORGET THE RETAINER ON GEAR SIDE IN EITHER STEP.

I've rode lots of miles on stock and modded 400's never done rod bearing yet. four different units with about 12000 miles total.
the bearing to crank fit on the pto side will wear before the rod. Loctite these bearings.
Loctite 640 is the best others similar 609, 603, 638.

I believe thread is m6x1.0 maybe m5x.8

 

I can only hope to get a little lucky and not have to pull that shaft. Thanks for the useful info. Loctite should be inside the bearing on the shaft or on the outside with the case surface?

 

Loctite the inner race to the crank

 

How well does loctite (red or blue?) hold up to the hot temp of the bearing when installing? Also I have a gasket coming for the crank but the book says loctite gasket eliminator, is this better than the gasket or included with the gasket? Also have a slide hammer blind hole bearing puller on teh way, think this will be needed? Thanks again for all the knowledge guys.