Good day all

I am new to this forum, but have found a lot of useful information here that guided and assisted me with my rebuild journey. For this reason I decided to join and would also like to share some photos of my rebuild should anyone be interested. I am also struggling to find the relative information and was hoping that someone out there can assist me with my current problem.

Long story short, I have a 2002 Polaris Scrambler 400 2x4. I obtained the ATV as a non-runner and there was a lot wrong with it. Honestly this motor was a mess!!! Waterpump failure, blown top gasket, motor rusted inside etc etc. I decided to completely rebuild the motor from bottom to top with new bearings, seals gaskets etc. (crank was still good). After a lot of research and many hours of cleaning and a way to much bucks spend, I successfully finished the rebuild.

Being a new motor I filled up my counterbalance with 100ml 10W30 oil as explained in the manual. I did everything as described in the manual in terms of bleeding the oil pump, radiator system etc. When I triple checked everything I started up the motor without to much of a hassle and it sounds amazing. I haven't ridden it at all because I want to make sure everything is 100% prior to taking it out. I have only started it up about 3-4 times in the last month or two.

This past weekend I noticed oil all over the motor as well as on the floor beneath the ATV. I narrowed it down to the breather/vent hose on the counterbalance casing (see photo). I saw that the oil pushes through this breather hose when the motor is running. I went to drain the oil in the counterbalance casing and I drained about 400ml of oil. Obviously this is 4 times more than what I put in there and the reason as to why it's pushing through the breather hose. I tried to analyse the oil to determine where it comes from. It is NOT milky in color so its not water mixing with oil from my waterpump (this was also redone in the rebuild as it was the main contributor).

It looks like oil mixing with oil and if I compare the color and smell to the 2stroke oil I am using, it looks like this is mixing. I have no idea how this is practically possible that the 2stroke oil can mix with my counterbalance oil? I am also not sure if it's only 2stroke and if it's a combination of fuel/2stroke mixing with the counterbalance oil. I am pretty sure I have everything installed in terms of gaskets, orings and seals when I did the rebuild.

I must also say that I have not removed the drain bolt on the crankcase to see if there is anything inside this casing and I want to do that asap.

Any help or advise will be much appreciated.

 

Just some more info on what I did to try and locate the entry point for the 2 stroke oil into the counterbalance casing; I firstly looked at one or two things.

1. I drained the counterbalance casing up until it only dripped one or two drops. I never filled it back up with the 10W30 oil and obviously didn't start the motor again afterwards. I left it for a day.

2. The next day I drained the counterbalance again to find oil in there again. Again this looks like clean 2 stroke oil. It wasn't a lot but there was still a stream of oil coming out

3. I also removed the crankcase drain bolt to see if the same substance (basically 2 stroke oil was in this casing) and there was just about nothing coming out. I only found a little bit of fuel/oil mixture (more like a vapor) - this is normal. Clearly not the substance what I have seen coming out from counterbalance casing

In my mind the only way that the 2 stroke oil can then enter the counterbalance casing is through the oil pump ...



I then decided to leave the ATV for another day or two and drain the counterbalance casing again to see if there is any 2 stroke oil in there again.

I left the ATV standing for two days and then opened up the drain bolt on the counterbalance casing last night to find clean 2 stroke oil in this casing once again... Remember at this point the ATV was just standing for 2 days, the counterbalance oil was previously drained completely and the motor was not started from the previous drain.

The evidence of 2 stroke oil once again just confirmed to me that the 2 stroke oil must be leaking from my oil pump into the counterbalance. The leak must be so severe, because it's leaking via gravity (2 stroke tank higher) into the counterbalance just from standing for 2 days.

I then proceeded to remove the oil pump and this is exactly what I found (see photo)... I left the oil pump, with supply line connected, hanging for about 5min and when I got back to the garage there was already a small blob of oil on the newspaper (see photo).






I do remember from re-doing the entire motor that I also spend a good hour or two on the oil pump by completely disassembling/cleaning it. Due to the motor being in the condition that I originally found it, the drive shaft of the pump was rusted and pitted quiet a bit (see photo). I tried to service it to the best of my capabilities, without realizing that it might leak 2 stroke past the shaft and oil seal.


Original condition of the oil pump before servicing

For now I can consider replacing the oil seal (bottom of pump) around the shaft, but I don't think this will resolve my problem due to the heavy pitting on the shaft. I think it will still leak to a certain extent.

I now basically have three options:

1. Have the existing shaft fixed up by an engineering shop and install a new oil seal in the pump
2. Try to obtain a 2nd hand pump somewhere (Not knowing the condition of this spare)
3. Remove/blank of the oil pump and run a Pre-Mix. I will need to search this Forum to find relevant advice and information to see if this is advisable and what needs to be done.

I hope that this information might be helpful to someone out there. Next time I will definitely test the pump prior to installing it into the motor and consider replacing the oil seal on the drive shaft of the oil pump.

 

Just some more info on what I did to try and locate the entry point for the 2 stroke oil into the counterbalance casing; I firstly looked at one or two things.

1. I drained the counterbalance casing up until it only dripped one or two drops. I never filled it back up with the 10W30 oil and obviously didn't start the motor again afterwards. I left it for a day.

2. The next day I drained the counterbalance again to find oil in there again. Again this looks like clean 2 stroke oil. It wasn't a lot but there was still a stream of oil coming out

3. I also removed the crankcase drain bolt to see if the same substance (basically 2 stroke oil was in this casing) and there was just about nothing coming out. I only found a little bit of fuel/oil mixture (more like a vapor) - this is normal. Clearly not the substance what I have seen coming out from counterbalance casing

In my mind the only way that the 2 stroke oil can then enter the counterbalance casing is through the oil pump ...



I then decided to leave the ATV for another day or two and drain the counterbalance casing again to see if there is any 2 stroke oil in there again.

I left the ATV standing for two days and then opened up the drain bolt on the counterbalance casing last night to find clean 2 stroke oil in this casing once again... Remember at this point the ATV was just standing for 2 days, the counterbalance oil was previously drained completely and the motor was not started from the previous drain.

The evidence of 2 stroke oil once again just confirmed to me that the 2 stroke oil must be leaking from my oil pump into the counterbalance. The leak must be so severe, because it's leaking via gravity (2 stroke tank higher) into the counterbalance just from standing for 2 days.

I then proceeded to remove the oil pump and this is exactly what I found (see photo)... I left the oil pump, with supply line connected, hanging for about 5min and when I got back to the garage there was already a small blob of oil on the newspaper (see photo).






I do remember from re-doing the entire motor that I also spend a good hour or two on the oil pump by completely disassembling/cleaning it. Due to the motor being in the condition that I originally found it, the drive shaft of the pump was rusted and pitted quiet a bit (see photo). I tried to service it to the best of my capabilities, without realizing that it might leak 2 stroke past the shaft and oil seal.


Original condition of the oil pump before servicing

For now I can consider replacing the oil seal (bottom of pump) around the shaft, but I don't think this will resolve my problem due to the heavy pitting on the shaft. I think it will still leak to a certain extent.

I now basically have three options:

1. Have the existing shaft fixed up by an engineering shop and install a new oil seal in the pump
2. Try to obtain a 2nd hand pump somewhere (Not knowing the condition of this spare)
3. Remove/blank of the oil pump and run a Pre-Mix. I will need to search this Forum to find relevant advice and information to see if this is advisable and what needs to be done.

I hope that this information might be helpful to someone out there. Next time I will definitely test the pump prior to installing it into the motor and consider replacing the oil seal on the drive shaft of the oil pump.