Ok my ATV just stopped on me yesterday checked compression was little or none however on strip down piston rings were partially seized on the exhaust port side
,ok new re bore and piston is ordered however oil starvation I suspect is the root cause
My question is how does the oil Pump for the two stroke direct injection work Is it venturi on demand with metering from the throttle cable or some other method either way I am not gonna waste a new rebore and new piston before I know how to test this pump also is it a good idea to premix for the first 200 miles help appreciated
Phil

 

If you are worried just unhook the oil pump and run mixed gas, then you never have to worry again.

 

Well of course im worried but it would be nice to know how to check if the pump actually works I intend premixing anyways my main concern is how to test it

 

<div class="FTQUOTE"><begin quote>Originally posted by: Philipx2000

Well of course im worried but it would be nice to know how to check if the pump actually works I intend premixing anyways my main concern is how to test it</end quote></div>

Bleed pump for air first(small screw at top of pump),disconnect oil line from cylinder,hold pump arm all the way up,turn engine over,should show a small dribble of oil out of line as engine turns over. Most people blame oil pump for seizures,when 99% of the time its just worn out pistons and rings,usually past due on top end work needed,BUT oil pumps can fail as well as any other part on the machine!

 

thank you Old Polaris Tech thats what I needed too know this was probably overdue a top end overhaul, I am a journey man mechanic but my experience is limited on ATVs I have ordered a Haynes manual off ebay so that will help I am sure, This was purchased to act as a snow plow and has done a good job until the obvious happened, other than that I am pleased with this old girls performance, thanks again I will be sure to check out the pump for defects and workability , just a note on the engine there is a check valve is that a one way valve for the oil injection?

 

Check valve is at base of cylinder,small line plugs into it from oil pump

 

Ok engine redone and starting to run it in everything is fine and I am pleased with the outcome rebored to 20 thou oversize rings were not filed I took a risk there but seems to be wearing in well ,I have one problem what is the jetting adjustment as I am going through a few plugs running the engine in and I have heard thats quite normal but the plugs are black due to I have put in a 40:1 mixture in the tank plus the oil pump is working so I am thinking maybe wait till the gas is low enough first then see how the plug is burning whats your thoughts?
250 1990 Polaris trail Boss

 

my 91 was rebuilt a year ago and still working off the stock oil pump watching on here you rarely if ever see a pump failure i feel really comfortable with these pumps they say polaris had the best oilers in the market.

 

Thanks ardakota its comforting

 

Also did you change those crank seals when you did the motor. If not you might consider them they are inexpensive and not too hard to install.