Scrambler 400 Pushing oil in breather hose - Polaris ATV Forum
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post #1 of 10 (permalink) Old 09-16-2019, 04:31 AM Thread Starter
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Scrambler 400 Pushing oil in breather hose

Good day*all

I am new to this forum,*I am 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.
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post #2 of 10 (permalink) Old 09-16-2019, 08:25 AM
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Sounds like the crank shaft seal is leaking - or the o-rings that go behind the spacers on the crank are missing - or the carb overflowed because the fuel was not shut off and filled the crankcase and the compression forced liquid fuel and oil past the seal into the counter balance chamber, but regardless how the chamber got over full - something is not right.

You need to do a crankcase leak down test - normal is 7 lbs psi for 7 minutes - if it's not holding pressure, a crank seal is bad, a gasket is leaking or it's leaking between the case halves.

Not knowing what procedures you used and how meticulous you were, it's even possible the oil pump is leaking into the counter balance chamber.

What kind of sealant did you use on the case halves?

There is only so many possibilities of how the counter balance got extra oil in it and fewer possibilities of how two stroke oil got in there.

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post #3 of 10 (permalink) Old 09-16-2019, 09:58 AM Thread Starter
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Hi Latebird

Thank you for the response. I am 100% sure that I installed all the seals as well as the o-rings behind the collars on the crankshaft. It might be possible that one of them got damaged (and I didn't see it) during the installation. For me it also make sense that this is about the only place where it could leak from the crankcase to counterbalance chamber. Is it possible that the 2 stroke oil can leak via the oil pump into the counterbalance?

I do not have the tools to do a leak down test and do realize this is a necessary for my problem... It will reveal a lot of useful information at this stage.

I used a Heat Resistant DenBraven Gasket Sealant.

One think that might be worth mentioning as well is that I realized the fuel tap on the tank does not shut off completely when in the OFF position. It still allows fuel to go through. Not sure if this might then be filling up the crankcase when standing, because I also noted that when the motor is running the is quiet a bit of excess oil (black) in the exhaust port and leaking by the gaskets on the exhaust knuckles.

I did setup/bled the oil pump according to the manual but it might even be throwing to much oil.
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post #4 of 10 (permalink) Old 09-16-2019, 11:10 AM
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Heat resistant or not, Den Braven sealants are silicone sealants - silicone is not gas and oil resistant - it will soften and blow out - cases should be sealed with an anaerobic plastic sealant such as Honda Bond, Kawasaki Bond, Yamabond or Three Bond 1184

If you should need to tear the engine back down, please use the correct sealant and make sure none has been pushed into the bolt holes - I have seen holes filled with silicone, the bolt torques against compressed silicone and although tightened to specified torque, the cases are not tight against each other

It would be unusual for an oil pump to leak around the drive shaft, but the pump is driven by the counter balance and any oil that might leak around the drive shaft would end up in the counter balance drive chamber

Liquid in the exhaust may be from excessive fuel or excessive oil - would be unusual for an oil pump to over oil to the extent of leaving the exhaust dripping - most people worry about the oil pump not pumping enough, but if the pump cable stuck with the pump wide open, it might, maybe, don't know - never seen it happen.

How did you torque the spanner nut on the RH end of the crank behind the stator? Maybe it came loose?

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post #5 of 10 (permalink) Old 09-16-2019, 11:50 AM Thread Starter
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Rookie mistake from my side with regards to the DenBraven Sealant... I will take note of the recommendation should I need to strip the motor down again.

I also can't see that that amount of 2 stroke oil can leak via the pump shaft into the counterbalance casing. I will also investigate the spanner nut behind the stator.

Just some more info; I just came from the garage now to look at one or two things.

1. So yesterday 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.

2. Tonight 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 (I must say that I did move the ATV from it's position where it was standing)

3. I also removed the crankcase drain bolt and there was just about nothing coming out. Just a little bit of fuel/oil mixture (more like a vapor). 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 am going to leave the ATV for another day and drain the casing again to see if there is 2 stroke oil in there again.

Thanks for all the help
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post #6 of 10 (permalink) Old 09-19-2019, 02:48 AM Thread Starter
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I found the leak...

So to get back to this thread and provide some information and pictures for those who might face similar problems...

I mentioned in my last post that I will leave the ATV standing for a day or two and observe any ingress of 2 stroke oil into the counterbalance casing. I have done that and 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.

As mentioned by latebird previously:
Quote:
Originally Posted by latebird View Post
It would be unusual for an oil pump to leak around the drive shaft, but the pump is driven by the counter balance and any oil that might leak around the drive shaft would end up in the counter balance drive chamber
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.

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.
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post #7 of 10 (permalink) Old 09-19-2019, 05:56 AM
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Ah yes - oil pumps are not serviceable - I am not aware of anyone who rebuilds oil pumps or where parts for oil pumps can be obtained. Also, I have never seen an oil pump fail unless it was run dry until it seized.

Best thing to do is find a used pump - test it by driving it with a cordless drill while holding it wide open (I believe they drive counterclockwise as viewed from the drive shaft and turning them backwards will not hurt them, they just don't pump when driven the wrong direction) - connected to an oil supply (just connecting a clear piece of tubing filled with oil is a supply) and spinning the pump at a low RPM, the oil in the clear tube should recede slowly and every few seconds a blurb of oil should exit the delivery port of the pump - I don't think I have ever seen an oil injector pump deliver a steady stream of oil - as long as the oil on the feed side is decreasing and is being pumped out on the delivery side, the pump is fine. If you turn it the wrong way, no oil will come out the delivery port and air bubbles may appear on the feed side.

Or, fashion a block off plate and seal the hole, but you will have to get a custom throttle cable or figure out a way to modify the split cable. If you decide to modify the cable by simply cutting the oil pump cable off at the splitter, hold the throttle wide open when the cable is cut. If you don't hold the throttle open, after the cable is cut and the first time the throttle is operated, the piece of inner wire of the cable will be pulled up into the splitter and may cause a stuck throttle.

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post #8 of 10 (permalink) Old 09-19-2019, 11:05 PM Thread Starter
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Thanks for the reply and advice on testing of the pump.

I will try and look for a 2nd hand pump but it doesn't look very promising at the moment. I tried to look online but didn't really see anything.

It looks like I will have to go for the block off option. I did some research as well and looks like this is not to much of a hassle to do. Some guys remove oil pump completely and go for a single throttle cable. In order to keep the split cable installed (still attached to the oil pump) I see they keep the pump installed and then empty the oil tank also blocking off on intake etc. I even read that one guy left the pump in and just removed the gear on the pump shaft, leaving the split cable connected to pump.

In my case I think will have to remove everything because of where my leak is situated. If I leave the pump installed, it will still leak the 2 stroke into the counterbalance. So I might need to consider a single cable then...

In terms of premix ratio I saw mostly 40:1. I think it will also be necessary to re-jet in the carbs due to the oil/fuel mix now running through the carbs where it originally was just fuel in the carb (2 stroke oil inlet on the 400 scrambler originally located at reed valve not on carb as per image)
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Last edited by JpMostert; 09-19-2019 at 11:08 PM.
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post #9 of 10 (permalink) Old 09-20-2019, 08:08 AM
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There are two listed on Ebay - both offered by muffsmotorsports - I have purchased from them before without problem

One HERE

the other HERE

Or you might try powersportsnation.com - there is plenty of used pumps out there - it's just a matter of finding one at the price you are willing to pay. They are easily tested using an electric drill to spin the shaft - I have a sonic cleaner with a cleaning solution solution that cost $100 a gallon - it will clean the oil pump nicely without disassembly (ask ronc80 how nice I cleaned his engine). If you are willing, I have machine tools at my disposal and a source for seals that I didn't have years ago when I was a green mechanic, I would like to have a junk oil pump to experiment with. I'll pay the shipping to get it and if I can fix it I will return it to you at no charge.

I can replace damaged overflow pipes in float bowls and would relist the opportunity to test my skills at refurbishing a two stroke oil pump.

If you opt to premix, start with mixing the oil at a 20:1 ratio - the 400L has a steel liner cylinder and needs more oil then a plated cylinder - you shouldn't need to re-jet the carb just to switch to premix - if you premix and start fouling plugs cut back on the oil, but don't go to less than 32:1 and only go to 32:1 if you are using a premium synthetic two stroke oil. If you go go to 32:1 and still foul plugs, the re-jet the carb about 2 sizes down on the main jet. Don't premix alcohol blended fuel unless you are using an oil that will mix with alcohol - the only oils that emulsify well (not mix) with alcohol are vegetable ester based oils. Full ester based synthetic and ester blended castor bean oil are good choices.

Mixing oil with ethanol blended fuel will force the alcohol to separate from the gasoline. Mixing a ester oil with alcohol fuel will make the alcohol molecules heavier and separation will still occur, but at a slightly slower rate.

The one constant that has been proven by the outboard boat engine manufacturers is that the more oil that is mixed with the fuel the more power the engine will produce and the longer the engine will last.

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post #10 of 10 (permalink) Old 09-22-2019, 12:12 AM Thread Starter
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Thanks for the Ebay listing. I will check it out and decide which route I will take. To replace or to remove...

I am located in South Africa and I think shipping the oil pump to you and back might be quiet expensive but thanks so much for the offer. I might still consider it. I already had to import just about everything i required on this ATV and spend quiet a bit of money on the motor, especially considering our exchange rate and transport/import fees...

I'm glad to hear that I don't need to rejet for the moment. I think I will consider going to premix then. I will follow your advice and look at the plug fouling. I am running normal fuel with a ester based full synthetic 2 stroke oil. My main jet should still be standard as in 230 as per manual.

Once again thanks for all the help.
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