OK, so here is an update.

I called the polaris dealer and went down to get the plug (bolt).
It was very busy and close to closing, so the parts guys were no help.

I went around and asked the service guys... an old man said drain everything, then pour oil in that hole until it runs out. SAE30, done deal.

I came in, looked at the manual and it was no help for anything but finding the recoil and starter drains. I took a few other bolts out, but got no drain.

So I put motor flush in that hole until it ran out. Then I turned the motor over slowly and splashed it out. Then I poured some down the dipstick hole and did the same. Then a little Mobil 1 0w30 down the dipstick hole too... which ran out that hole pretty easy.

I plugged it up and filled with the 0w30... which was very hard to see on the dipstick... so rather it is full or not I don't know... but I do know it has at least the 2.5 oz the manual calls for in it.

I'm very frustrated at this point.... I gotta have an illustrated parts list and a repair manual for this thing. The owners manual is useless.

 

I would change that oil frequently a few times after riding instead of just topping it off, just in case the motor flush missed anything. I can only imagine what went in the hole. Has anyone found out what that hole is for?

I saw another thread that said where a parts list is. I think you can see it at the Polaris website after you sign in. I FOUND IT. http://parts.polarisind.com/Browse/Browse.asp

 

Thanks jumbofrank!

If you go there, then to ATV and select 1999 Sport 400 A99BA38CA and then to crankcase and cylinder.... it's #43.... oil guage.....

So maybe the old man was right?
Maybe it is there for oil filling until it runs out?

Where is the dang drain plug then?
On the bottom of the recoil is the only place I find a similar plug.
The others are screws with 10mm heads, like at the starter....

 

I think that's the dipstick. To me it looks like #27 is the plug. I still can't figure out what the hole is for, but the plug has a gasket, #28, and it shows the drain plug and gasket below them, #4 & #3. Hey, you can zoom in too! Right below the print button click 70, 100, or 130%. It looks like the plug hole goes down to the drain hole.

 

Yeah, looking harder I see what you are saying.

We are looking at the back of the engine it that view... recoil area being closest to us...

So #27 is the plug I bought... #35 would be the recoil plug... and #4 the drain...

So tell me... where the crap is that #4?

It would appear to be a bolt that on the machine appears to be a motor mount bolt?

 

Well it SAYS drain plug. Maybe it's not. I looked again and it looks like it goes into the right side, NOT the bottom. I think that's where the counter-balance oils drains out when you change it. I'll be F@#$%^ if I know!

 

Well, I have looked over everything I could find on this.

The best that I can tell, all of the drains except the recoil drain must be those smaller screws that also have the phillips head in them. These are smaller than I expected for a "drain" but must be....

I plan to drain that oil I put in tomorrow.
I'll remove the one to see if that is right then.

 

Run it to splash the oil around. It might knock more dirt loose. Good luck Duster.

 

the counterbalance drain is a 10mm bolt next to the starter.you'll have to remove the skid plate to get to it.the plug thats missing i think is to put oil in the counterbalance.

 

Hey Frank thanks for the link to Polaris parts brower. The way I tear thins up I need it. By the way dont buy anything used from me