I was using my 2000 400 4x4 to pull a friend on a sled in the snow (in the middle of our current portland blizzard) and the overheat light came on after about 45 mins of fun. It was on for a couple seconds then the bike shut off. Now it wont start. I have not had a chance to check much soo far but I figured before I start ripping into it I would see if anyone has had any experience with overheating and what may have caused it. I am pretty sure it was getting oil cause it was smoking fine here and there and I could smell it in the exhaust but I am not positive of this (because it is an injector and can screw up). It is 20 degrees here and the fan was coming on and shutting off on its own periodically. It was sounding kinda funky while I was turning it over after the initial failure. I am guessing that it (the funky sound) is because the starter was surrounded by snow though. Thanks for any ideas you can give me before I dig in too deep.

Jarrod

 

The 400's were prone to some head-gasket problems when pushed hard. Also, with the temp change did you ever check your jetting? Although jetted pretty rich from the factory, when the temps fall in the winter months, richening things up is a good idea. Does the motor turn over at all? Sometimes even after a sieze, they'll break loose and run....though at that time it's still a good idea to rebuild the top end. Also, just prior to stopping, did you notice any metallic type noise? The piston skirts sometimes let loose, and the "free parts" will make some racket just prior to stopping things. Other than damaging your electric start, maybe gently try to rotate the motor using the pull handle. Also, did you ever check the coolant level, and or flush the radiator out to clean out any lodged mud?

 

Hey thanks for the prompt information guys...

I took a quick look at it a little while ago, it does turn over and I do have good spark and plenty of gas and oil (visible on my hand after turning it over with spark plug out and my hand over the hole). Couple other things I checked; coolant level was good and oil tank is full, it does sound different when I am turning it over then it did before the failure. It doesnt sound metalic, I would actually kinda say it sounds like it doesnt have much compression (if it is possible to hear such a thing??). I didn't hear any strange sounds before the failure, and there was no change in operation either. I would say that we might have been pushing the revs a little with the ice and snow and pulling a sled. Man that was fun, thought, I would not say that it was worth a top end job. Is it hard to rebuild the top end on this engine?

Thanks again for your help with my stupidity...

 

Hmm, and who fixes jets? [img]i/expressions/face-icon-small-smile.gif[/img]

Actually sounds like a compression test is in order. If you don't have a good reading, then the top end will have to come off. Not a hard job, just a bit time consuming. And you can do all the work at home. I would suggest getting a maint. manual from your local dealer and reviewing the steps prior to starting. Get yourself a Wiseco piston for a replacement. You can have you local tech mic the bore to see if you just need a honing, or a boring. Do this prior to purchasing the piston. When all is said and done, make sure to re-torque the cylinder base bolts after the new rebuild has been thoroughly heated up the first time.

If you don't want to deal with your dealer, or live a ways away. Shops like HPD, Hot Seat, and Rick Ritter...oh, Aaen too, can help you with getting you back on the trails.

 

I was thinkin the same thing (compression test in order). I am not looking forward to the results I am expecting to see. I expect that I can do all the work myself (minus anything you need a machine shope for). So I guess that is my next question... Depending on the damage that I see when I start to look deeper into this thing this weekend, do I HAVE to hone the interior, or is that only if it has some damage? Do I have to replace the piston, it seems (to me the amateur) that what ever damage I did will be minimal considering it turned over right after with no problem and I hear no rattleing. Am I asking these questions too early, maybe I should just tear into it and find out for myself.

But out of curiosity what does a top end job usually consist of? I thought it was just rings and maybe valves but I am just begining with 2-strokes.

Thanks

 

On a 2 stroke, Top End job usually means new piston, rings, wrist pin, circlips, wrist pin bearing, cylinder boring, and gaskets.

You will also find that on the Polaris 2 strokes, the compression has to be above 100 psi in order for it to run.

JMO - if you are going into it, you might as well do the whole top end to begin with, otherwise you will be back in to do it again in no time.

 

JUst to give you so info there are no valves in a 2 stroke you will need bore job always to make the barrel true round agin you will need piston,rings and gaskets you might think about a port job for more power and new vforce reads you will spend between 350 to 800 dollars depending on what you do this is if you put it together your self

 

sounds like the rings lost their tension
deglaze the bore and install fresh rings as long as there are no major scratches to the cylinder wall or piston your good to go

 

Well thanks for all your help!!! I took the head off and found some melting on top of the piston. I then took the cylinder off and found the the culprit was the rings. They melted to the piston. Found some very slight scoring (probly less than .001). Ordered wiseco piston kit(standard size), gasket kit, and wrist pin bearing from ebay. I think I should have it going by this weekend.

I have some other questions for you all.

In order to do the top end I have cleaned out the cylinder and the head and have honed out the cylinder to create a crosshatch pattern, then cleaned the cylinder very well. I was wondering if any of you feel I should replace any other fluids along with this project (other then the obvious radiator fluid), and what mixture of gas should I use for the first tank? I have seen some things that say 40:1. What should I coat all the parts in for the initial startup. A friend said that the 2 stroke oil that I use for mixture would be a good things to coat everything in for the assembly.

Also, I believe the main culprit for this failure mode was the buildup of snow around the oil injector housing. The injector sits in such a place that any snow that is tossed by the wheel gets packed right around the injector. I think this cooled the oil till it became goo. I am sure that the injector does a poor job of injecting goo. I still have to test my theory and test the injector before I start it up the first time.

Thanks again, will try to keep you all informed.

 

piston work aside

I would also be sure to pin-point the cause of your overheating and be sure to remedy it.

No fun fixing stuff twice[img]i/expressions/face-icon-small-wink.gif[/img]