I have a 1996 Polaris Sportsman 4x4 400 2 stroke, and the other day when the wife was riding, it just died.
I tore down the engine until I found the issue, a nice hole in the piston head.
But, I also noticed that the oil reservoir was still full. She put on some miles that day, about a half tank of fuel, so I assume the oil would have gone down as well. But, it's still as full as it was when I filled it in the morning.

While I have the engine apart, is there any way I can test the oil pump itself, to ensure it's working. I'm thinking by the engine not getting or using oil, that contributed to the piston blowing out.

 

Welcome to the forums.

I'm sure someone will give you the instructions on testing the pump. I don't have them. If the line isn't clogged, I'd say it's the pump.

That being said, I'd consider just replacing it or getting an oil injection block off kit. Looks like getting a new one will be hard, as they don't make them any more. Several used ones for around $25 on ebay.

 

Thanks for the reply.

It looks mechanical, not electrical, so I'm probably going to pull it and take it apart to check for clogs and such.

 

Over many years of 2 stroke engine service I learned the hard way to never trust oil injection systems. Yes there are many that swear they work well, but having seen numerous marine and sport engines destroyed by failed oil injection pumps, I always just blocked them off and mixed oil/gas together. Never had an issue with mixed oil/gas!

 

This is my first ATV, and my first 2 stroke engine. I've only had this atv a little over a month, and until a few weeks ago, it wasn't driven (by us) at all.
But, going forward, I think I will bypass the oil injection and just go with a 50/50 mixture.

I wave been reading, and was wondering if you needed to adjust your carb at all, to make it accept the gas/oil mixture, or if it ran fine without adjustments?

 

Take a look at this thread about the oil pump on a 400. It tells how to do the adjustment after you clean up all the dirt that's probably in there. Anytime you rebuild the engine, premix the first tank of gas/oil 40:1 so you don't burn up your engine. Once you get the pump adjusted and your premix in the tank, crank it up and with the oil line disconnected, hold the pump lever wide open and you'll be able to see if any oil is coming out or not. If it is, hook the line back up and keep an eye on your oil level to see if it goes down. They don't burn a lot of oil but it should use some. Your exhaust will be really smoky until you use up the tank of premix and switch back to just gas. If no oil is coming out when you hold the pump lever all the way open, you still have work to do. Instead of fixing it, it sounds like you want to quit using the oil injection and premix 40:1 all the time. There are lots of threads about it if you use the search box in the upper right corner of the page to search for 400 oil injection pump block off.

https://atvconnection.com/forums/pol...djustment.html

ETA: If you do a proper oil pump block off you shouldn't need to adjust the carb. The oil injector ratio is somewhere around 50:1 but if you premix go with a 40:1 mix.