I recently bought a 1999 Scrambler 400 4x4, my first ATV. Have any of you other Polaris 2 stroke owners had any problems with the oil pump? I haven't yet, but I have owned a number of jetskiis over the years and I always remove the pumps and convert them to premix because some skis, especially the early Kawasakis, had a tendency to shear the pump drive and run the engine out of oil with no warning. I had it happen once and I had to rebuild the engine - after a long swim home. So my first instinct was to do the same on my 4 wheeler, but I thought I'd see if it had ever been a problem with anyone before I did it.

 

I'm not aware fo any problems with the system. I think most people do it either to eliminate the possibility of a problem, or because the injector wasn't designed to work with a lot of the motor mods available IE: porting, bigger carb, ect.

 

KEP,

From my understanding and research on this topic (I also have a Polaris 400 2-stroke), Polaris used a plastic drive gear when they first came out..........over time, the gear would wear out, and the pump would no longer supply oil to the engine (I believe this was not a widespread issue, but happened more often than now). Now, the pumps have a metal drive gear. Like AZ400L said, people mainly eliminate the injection either to ensure the engine is lubricated, or with the addition of mods. Personally, I removed mine because of the fact that a cheap part is being used to protect an expensive one, and premixing is easy enough. Throttle pull is also easier without the injector, and some people even eliminate it to reduce the weight of their quad. Removing it and going to premix just gives a little more peace of mind. Either way, you should be ok.

Waylan

 

On a stock or trail modded 400 the oil injection system works great. If you remove it your quad will smoke much more at an idle.

 

Walexa, that was the problem on one of my SeaDoos, it had a plastic oil pump drive gear that stripped out - a cheap part protecting an expensive one! And I like your point about easier throttle pull. I think I'll elimiate it just to be one the safe side, plus, as a diehard motorhead, I like the way premixed Castor 927 smells anyway! Thanks for the input guys!

 

On the newer machines, shearing off the pump drive has become very rare. More often, the cable will fray or rust (usually because water got into the 'box' on the lower front of the engine where the injector pump is). If it frays & breaks, your engine will be starved of oil at higher RPMs, and if it rusts 'open' your engine will be flooded with oil at idle.
Keep in mind, once you go to premix, you will have to use premix, no borrowing a gallon of gas off of someone to keep riding. If that doesn't bother you, there is no real reason NOT to do it, if you want the piece of mind.
Commonly, what I see is the oil tank becomes another 'reserve' gas tank. If I am not mistaken, I think it holds about a half gallon.

 

If you do any cold weather riding, which might include water, the pump and cable (on the 400) has a tendency to freeze up overnight. Nothing a heat-lamp in the morning can't solve, but like the others stated, why bother, premixing is easy. Besides that full oil tank is around 11 pounds of dead weight sitting up front. Lighter = Faster.

Ken

 

what years have the plastic driven gear?

 

KEP: on your point about Maxima 927, it is a good oil to use, but is really designed for high revving (10K+RPM's) motors. A fully modded Polaris like mine will only turn about 8K, which according to the people at Maxima will not fully burn the castor, potentially causing a large build up. They suggested using their other products, which I will as soon as I finnish this bottle of 927...

If I still have my bike, anyone looking for a nice 400? $4500!