I am looking for some help diagnosing an oil pressure problem on a sportsman 700.
The motor ran dry on oil and wiped out a rod bearing. Tore the motor down and replaced the crank assembly. Once assembled the motor fired right up, but it has no oil pressure. Where I need help is as follows:

I did not replace the gerotor assembly on the oil pump because it looked ok. I have since pulled the side cover and verified that the pump and gerotor are spinning. It doesn't seem like any oil is making it to the pump assembly.

I've tried priming the oil pump several times but to no avail. I can crank the motor with the primer plug out and oil filter off and I don't seem to get any oil flow whatsoever. If primed improperly would the pump really run dry for a prolonged time ? It seems upon firing up, it would self prime.

I think I am either completely missing the boat priming this thing, or the gerotor assembly got worn when the motor ran dry and blew, or I have a problem in the case ports or the oil pickup. My next step is to split the case again to check pickup and look for obstructions internally.

My crank case has some 'slight' wear marks where the oil pump gerotors run against, would this cause a loss of oil pressure ?

Thanks in advance for any help or further thought !!

 

Should feel resistance after you force in about 3 ounces of oil in the adapter tube. Fill the oil filter about 1/2 full and install. Even without priming the oil pump should build up pressure,but if not,then I'd tear it down.Plus you can remove the oil pressure relief valve bolt,spring and dowel and use a little compressed air to clear any possible obstruction,replace and try priming again. May or may not help.

 

Thank you for the reply !! I'm going to bust it apart again just to be safe, and I'll advise. I've learned so much from your past postings over the years, thanks for always taking the time to spread your knowledge !!

 

So, I pulled the motor again, split the case. I was disappointed to find that the pickup, case, oil gallys and oil ports are all clean as a whistle.

I will need to go back to focusing on the pump itself. At this point, I can only imagine it can be a few things.

I see that the case sealant was a little light in the area around the oil port from the pickup up to the oil pump. I am wondering if that could cause some loss of suction or something.

Secondly, the manual is pretty specific on sealing the oil pump bolts up. I just used some small dabs of blue Loctite. I will try to apply a sealant to the threads.

I am really wondering if the seal between the oil pump and the crankcase is important ? I have some slight wear and I was considering a touch of case sealer on the oil pump flange to try to seal it off.

I am also planning to replace the pump and gerotors, even though they look OK to the eye.

 

Look back at the oil pump install section in your manual. Gerotors can wear along with the pump housing,but other factors involved also. The pump assy needs to be greased up throughly with moly or lubriplate and the criss cross torque sequence on the 4 bolts is critical @7 foot pounds.The grease aids in priming the pump quickly. Plus as you torque the bolts,turn the oil pump shaft to make sure the rotors aren't binding.