Two stroke oil pump operation??

[hytron]

So I took my oil pump out of my 787 RFI to test it out. The service manual calls for 5.7-6.9mL out of each port while spinning the shaft for 5 minutes and holding the pump lever FULL "throttle", I measured 6.3mL which is within the spec. I was curious to see what happens at idle, and aligned the marks on the pump same was as the pump is on the running idling engine. While spinning the pump shaft I get NOTHING to come out of the small oil lines. I borrowed another pump for 787 RFI from my friend (used) and it had exact same result.

So do these engines NOT get lubricated at idle??? It is hard for me to believe that this is the case! Any inputs would be greatly appreciated!

 

[LouDoo]

Yes the motors get lubrication at idle, but the purpose of the oil pump is to provide variable lubrication on demand when needed, not much lubrication is required at idle speed.

Lou

 

[Sportster-2001-951C-Stock]

That's true, the oil pump meters zero or near zero oil at idle, it's not much if any. This is normal. There's a pretty decent puddle of oil that builds in the crankcase during cruise though, it's enough for most any rider so there isn't any chance of lubrication issues unless you idle extensively (like most of the time).

If you troll mostly, then you could adjust the pump to deliver slightly more but notice if you adjust too far the oil can stop flowing at full throttle due to an over-traveled valve position.

Best I can account for, mine averages to about 65:1 ratio and I operate mostly around 1/2 throttle.

 

[Bonmotwang]

What if I idle out a long no wake area? Will the oil enough to lubricate the cylinder wall and piston?


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[Bonmotwang]

Sporster I knew you will jump in. LOL


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[hytron]

Ok so here is the update. I applied a slight vacuum on one of the oil lines (just like it would exist while a motor is idling), and while the pump was at the idle aligned position, it took exactly 2 minutes for oil to move one inch. My drill is running at 1150rpms. So appears it does get some lubrication at idle, but is that adequate? Apparently the initial synchronization is very critical and important.

Repeating the same test without vacuum applied, in two minutes oil moves in the lines by about 5/16 of an inch.

There are a few areas where I live, where you have to idle for almost 15 minutes...Is that a concern for this machine?

 

[68ragtop]

I tested a pump a year or so ago from a 951 It flowed oil at 1500 RPMS with the hash marks lined up. If I remember correctly, the pump can seemingly stop pumping if the alignment marks are way off. at 1500 RPM's the movement is sloooooooooow

 

[pwgsx]

Are you spinning the shaft in the right direction? In REVERSE?

 

[hytron]

68RAGTOP, 951 dispense slightly more oil than 787RFIs (from the service manual), but yes that makes sense.

PWGSX, yes in reverse,

 

[jimmaki]

Ok so here is the update. I applied a slight vacuum on one of the oil lines (just like it would exist while a motor is idling), and while the pump was at the idle aligned position, it took exactly 2 minutes for oil to move one inch. My drill is running at 1150rpms. So appears it does get some lubrication at idle, but is that adequate? Apparently the initial synchronization is very critical and important.

Repeating the same test without vacuum applied, in two minutes oil moves in the lines by about 5/16 of an inch.

There are a few areas where I live, where you have to idle for almost 15 minutes...Is that a concern for this machine?

If it pumps almost four times as much oil with whatever vacuum you are using, then how much vacuum becomes a critical variable in your test. How did you determine how much vacuum to use?

Perhaps a more accurate gauge would be to empty the small oil lines and run the engine on idle on premix at 40:1 and see how fast/far the oil moves in the small oil lines. Make doubly sure the pump is primed and no air bubbles are in the supply and the alignment marks are lined up for your idle stop setting.

 

[Sportster-2001-951C-Stock]

If this is a carbed ski, you have the option of adding some premix to the tank. Don't do that if it's fuel injected. There are numerous other ways to add syrup as needed depending on circumstances.

 

[hytron]

JIMMAKI I agree with you that would be a true test, however that requires slightly more work but is not excluded. The source of vacuum was my mouth so I do not know the exact amount since I did not use any gauges. These engines have rotary valve, I think using just premix could cause that a problem as the valve would not get any lubrication?

The drill speed was precisely measured using one of the digital laser photo Tachometers.

I am thinking if running the oil pump about 1/2 millimeter advanced (alignment marks) would not cause any problems and the WOT would still get a full flow of oil required.

SPORTSTER, this is 787 RFI.

 

[jimmaki]

JIMMAKI I agree with you that would be a true test, however that requires slightly more work but is not excluded. The source of vacuum was my mouth so I do not know the exact amount since I did not use any gauges. These engines have rotary valve, I think using just premix could cause that a problem as the valve would not get any lubrication?

The drill speed was precisely measured using one of the digital laser photo Tachometers.

I am thinking if running the oil pump about 1/2 millimeter advanced (alignment marks) would not cause any problems and the WOT would still get a full flow of oil required.

SPORTSTER, this is 787 RFI.

On carbed engines the oil is injected at the rotary valve cover before the valve and the fuel comes in before the valve as well. The rest is lubed by oil bath independent of the fuel. Since I see yours is RFI, running premix not recommended. For a short test though, I don't know especially at an idle mix of 100:1 or so. If in doubt you could squirt a shot or two of oil down the carb throats which should be enough for a short test at idle.

I read somewhere that if the alignment is too far advanced then the engine wouldn't or might not get oil at WOT. If you're running stock FAs and other front end air intake parts, I'm pretty sure the manifold pressure is a whole lot less than you or any human can develop with your lungs, especially at the oil injector nozzles on the engine side of the closed butterfly plates.

 

[Sportster-2001-951C-Stock]

It's not clear to me there's an actual problem, I guess if you were experiencing some sort of lubrication issues then it might be worthwhile attempting to compensate.

 

[hytron]

Yeah I read that somewhere too, so the safest way is to do a bench test of the pump at different lever positions. What I would probably have to do is measure how many degrees the pump lever turns from idle to WOT and test how far it can be advanced without compromising the amount of oil at WOT. I assume a few degrees +/- would be within the tolerance of the pump.

 

[jimmaki]

Yeah I read that somewhere too, so the safest way is to do a bench test of the pump at different lever positions. What I would probably have to do is measure how many degrees the pump lever turns from idle to WOT and test how far it can be advanced without compromising the amount of oil at WOT. I assume a few degrees +/- would be within the tolerance of the pump.

I don't know but it seems like a lot of work to find a solution in search of a problem. I'd set the marks dead on per spec and go with that. If you aren't getting sufficient lubrication at idle then maybe time for a new oil filter or new oil pump. It's possible the oil injector nozzles could be clogged. But if any of these things are not working as designed, you'd have issues across the entire power range and especially at WOT and midrange, not just idle.

The low manifold pressure at idle is considerable. Not sure what bench testing will tell you. It varies non-linearly as the throttle plates open and the air velocity increases. It is a lot less at WOT at the oil nozzles. You might be playing with fire (pun intended) where your engine is concerned.

Also, too much oil is not necessarily more-of-a-good-thing is better for your engine. Quite the opposite.

 

[hytron]

Ok here is some background how all of this started. About a month ago I was out on one of the lakes and this particular lake has about 10-15 minute idle just to get to the ramp. Got the seadoo out of the water, started it, hit the throttle twice to get rid of all of the water as we always do, and as I let it idle for a second, I heard a weird noise (like a tractor, diesel engine noise) coming from the engine. It all happened so quickly, and these machines idle out of the water at 2200rpm, the rpm kept dropping down to almost 1600, at which time I stopped the engine on the button. Tried restarting it, the started would only click. Tried again, only a click. I assume the engine was seized at that time. I left it alone for about 10 minutes and I was able to restart and ran normally. Took it home, ran normally when I started just for a few seconds. But this incident was a concern because many times I go out on St. Claire here in Detroit, which is a huge lake and not a good place to experience any issues or seizures with the engine. When this machine was new (back in 2005) rode it for 30 hours and the engine seized. It happened right when I squeezed the throttle coming our of no wake (idling for over 10 minutes here). PPG rebuilt the engine for me under manufacturer's warranty and had not had any issues for all these years!

*** MAINTENANCE *** This machine gets a new oil filter and new spark plugs EVERY spring before the season starts regardless of their condition. RAVEs get cleaned twice a season or approximately every 15-20 hours. Jet pump oil gets replaced EVERY season regardless of its condition. Always properly winterized and stored with fogging oil and RV coolant to purge all the lake water out. Someone might say way overkilling but I like to make sure it starts when I want to go out riding :lols:

So continuing my story... pulled the RAVEs out about a month ago, found some water droplets on the MAG side RAVE (on the top of the metal - not the stem), so I kept thinking that a gasket failed. Pulled the tuned pipe and the exhaust manifold, I was hoping to see a failed exhaust and no signs of gasket failure. I cleaned everything and put it back together and torqued to the specs. After an hour back on the lake I spotted some air bubbles in the small oil lines coming out of the oil pump (yes there is another thread on this one right here on this forum). Tried bleeding the pump, no air came out, no air that I see in the filter or oil supply line. Went out riding again a few days later, and after 2.6 hrs on the machine when I came home I saw a few small air bubbles in the oil lines (this time she bubbles were smaller). During that riding time no issues on the lake. WOT ran great. idling for about 5-10 min had no issues either.

So I am now concentrating on the pump and trying to figure out what happened at the first place and why the engine seized (the seizure from a month ago was momentary and I think I stopped the engine at right time as no damage was done to the pistons - inspected with the camera).

Adjusting the oil pump correctly what they call "initial synchronization" can be tricky and depends from which angle you look at the lever. I cannot see my pump alignment marks and I have to use a small shop mirror. At the same time my eye has to be looking from the direction and angle of the engine tilt otherwise you can get a false reading. Sometimes is worth to take the pump out just to look at it straight down and see the alignment marks. Just as a verification (and yes I know that can be off too because of the different cable angle.

 

[jimmaki]

Ok here is some background how all of this started. About a month ago I was out on one of the lakes and this particular lake has about 10-15 minute idle just to get to the ramp. Got the seadoo out of the water, started it, hit the throttle twice to get rid of all of the water as we always do, and as I let it idle for a second, I heard a weird noise (like a tractor, diesel engine noise) coming from the engine. It all happened so quickly, and these machines idle out of the water at 2200rpm, the rpm kept dropping down to almost 1600, at which time I stopped the engine on the button. Tried restarting it, the started would only click. Tried again, only a click. I assume the engine was seized at that time. I left it alone for about 10 minutes and I was able to restart and ran normally. Took it home, ran normally when I started just for a few seconds. But this incident was a concern because many times I go out on St. Claire here in Detroit, which is a huge lake and not a good place to experience any issues or seizures with the engine. When this machine was new (back in 2005) rode it for 30 hours and the engine seized. It happened right when I squeezed the throttle coming our of no wake (idling for over 10 minutes here). PPG rebuilt the engine for me under manufacturer's warranty and had not had any issues for all these years!

*** MAINTENANCE *** This machine gets a new oil filter and new spark plugs EVERY spring before the season starts regardless of their condition. RAVEs get cleaned twice a season or approximately every 15-20 hours. Jet pump oil gets replaced EVERY season regardless of its condition. Always properly winterized and stored with fogging oil and RV coolant to purge all the lake water out. Someone might say way overkilling but I like to make sure it starts when I want to go out riding :lols:

So continuing my story... pulled the RAVEs out about a month ago, found some water droplets on the MAG side RAVE (on the top of the metal - not the stem), so I kept thinking that a gasket failed. Pulled the tuned pipe and the exhaust manifold, I was hoping to see a failed exhaust and no signs of gasket failure. I cleaned everything and put it back together and torqued to the specs. After an hour back on the lake I spotted some air bubbles in the small oil lines coming out of the oil pump (yes there is another thread on this one right here on this forum). Tried bleeding the pump, no air came out, no air that I see in the filter or oil supply line. Went out riding again a few days later, and after 2.6 hrs on the machine when I came home I saw a few small air bubbles in the oil lines (this time she bubbles were smaller). During that riding time no issues on the lake. WOT ran great. idling for about 5-10 min had no issues either.

So I am now concentrating on the pump and trying to figure out what happened at the first place and why the engine seized (the seizure from a month ago was momentary and I think I stopped the engine at right time as no damage was done to the pistons - inspected with the camera).

Adjusting the oil pump correctly what they call "initial synchronization" can be tricky and depends from which angle you look at the lever. I cannot see my pump alignment marks and I have to use a small shop mirror. At the same time my eye has to be looking from the direction and angle of the engine tilt otherwise you can get a false reading. Yesterday I actually took the pump out just to look at it straight down and see the alignment marks. Just as a verification (and yes I know that can be off too because of the different cable angle.

It's possible you're attributing some symptoms to the lack of oil that might indicate other problems different than where you are looking. The diesel engine noise and the water droplets could be signs of water or steam getting into the combustion chamber and causing very high pressures while also condensing water droplets on the raves. Considering how hot they get, for any water to remain there would seem to indicate a considerable amount of water vapor going by them. That would also lower your idle rpms the way you described and eventually lock up the engine. After the steam condensed or the water drained, it could possibly start and run again.

Pressure test your cooling system really well. If your engine uses one, was the same water pump put on the rebuilt one by PPG?

As far a bubbles in the oil injection lines but none in the filter or pump feed line ... could be a crack or leak in the pump output barbs where they attach to the pump, or in the lines themselves. Again, the manifold pressure is very low at idle where the injections nozzles are so even if you don't have a leak letting air in, the pressure could be low enough to force any gasses in the oil to come out of solution and form bubbles. Your oil pump is probably ok if it runs WOT without issues. But it's cheap enough insurance and probably worth your peace of mind to replace it.

I wouldn't think the small amount of parallax error using a mirror to align the marks would be enough to cause the symptoms you're describing. If you don't think you're aligned perfectly then err a tad on the rich side and rest easy.

 

[Sportster-2001-951C-Stock]

Periodic rebuilding is considered preventive maintenance, otherwise every 2-stroke will eventually seize. The ONLY exception is when it's rebuilt before before that happens. Just as there are 2 types of wooden structures, ones that will eventually have termites and ones that already do.

That said, I've never seen a 2-stroke damaged by having more oil than is necessary but I've seen them seize just about every time, when there wasn't enough.

So how much oil is enough? Upon tear down you will want to see a large enough oil puddle in bottom of the case to wet the crank wheels. If there's less than this there wasn't enough.

I'm not certain only b/c I haven't tried myself, but I think you should be able to modify the oil pump internally, in the case you want to "crank it up" a bit. I think you might be able to change just the low flow without changing the high flow.

 

[hytron]

I didn't pressure test the whole cooling system, just did a plug-and-mouth-created-pressure on the other end. This machine is cooled by the lake water, so the source of cooling is coming from the jet pump. Before I pulled the exhaust manifold off, I checked several areas just to make sure the leak is not obvious. The only way that I can think of for water to get in the combustion chamber is through tuned pipe to exhaust manifold gasket, manifold to cylinder gasket or cylinder base gasket (jug base gasket). This machine also has a crankcase heat exchanger, and that is a sealed area under the bottom half of the engine and magneto heat exchanger which is located on the front part of the engine and is also sealed from the internal components. I highly doubt that casting of the engine broke or cracked somewhere and there is a leak, but I will definitely have to do a cooling system pressure test. I assume not more than 5 PSI?

As far as the oil, I am going to the lake tomorrow to test it out for a few hours so I will post the updates. If I see a single bubble in the oil line I can definitely call a bad oil pump. WOT was never a problem...the first time it seized was after idling for a while. I think I will take your recommendation and advance the pump a tad just to be safe.

I have also heard that crank bearings on these motors go bad over period of time and have to be replaced. So like what Sportster said, if there is enough oil on the bottom of the crankcase that should be an issue. I still have about 130PSI compression on both cylinders which kindda tells me that the top end is somewhat OK shape.

As far as the oil pump disassembly goes, a friend of mine gave me an oil pump from 787RFI that he didn't need, it is used so I have been comparing the two but still getting same results as of now.

 

[jimmaki]

Right 5 psi longer the better. Pump pressure is highest WOT.

 

[jimmaki]

If you don't find a leak in the cooling system, the only other way I can think of water getting in the engine and on the raves is if it's ingested through the carbs, either from something splashing/spraying water on the air intakes, or possibly in though the fuel if it has phase separated in your tank. Check your water separator/filter and/or just draw some fuel from the carb in line into a glass jar and see what settles out if anything.

 

[hytron]

So I took it out on the lake this past weekend and seems like everything is working ok. Still get 6700rpm and 50mph on the GPS. When I took the seadoo out of the lake the first day, I still saw some air bubbles in the small oil lines (one bubble in each of the lines). No bubbles after the second day (after 2.5 hrs on the machine). So I am not sure what to think at this point other than the oil pump getting bad. It is unlikely to me that both oil lines are broken/cracked and if they are I am not seeing any oil spills or drips from the pump area. I am still suspecting the pump shaft seals to be going bad.

 

[jimmaki]

The oil pump isn't self priming as we all know too well, so I wouldn't think it would develop negative pressures to draw in air through the seals. If you don't see oil spills around under the pump the seals and lines are most likely good. If you ran it 6700rpm long enough to get to 50mph, you'd know if the pump were bad.

It may not help your motor but if if makes you feel better, why not buy a new pump and put it on there and see if you get bubbles? If not, toss the old pump. If so, now you have a good spare.

[EDIT] If you have one of those oil change vacuum pumps, try pulling a vacuum on the line to the pump and see if you can draw any air out of the oil filter, oil line, connection to the tank, etc. If not, then try pulling a vacuum on the small output lines and see if you can pull any air out of the pump or the lines.

 

[Sportster-2001-951C-Stock]

Have you cleaned the intake manifold oil injection nozzles by flowing solvent through them? I'm pretty sure ours have checkball valves in them. I think it's a good occasional PM item to clean them out, not that this would cause bubbles but flow issues....

Anyway, I guess a couple of air bubbles in the oil lines indicates there was some air not purged from the oil pump. I can't see my oil lines without going through an act of congress so can't tell you if there are bubbles in them.

Noe there are no bubbles in your lines, hopefully it remains that way. At lest they were downstream of the oil pump and should've purged out quickly so it's surprising you saw them at all.

Please keep us informed on this subject though.