counterbalance oil type

[mikidymac]

Sorry IDoSeaDoo, nice catch, I revised my post to indicate counterbalancer seal and not labrynth seal.

The oil/air/fuel mixture is more than enough to lubricate the bearings and gears of the crank and counterbalancer. Every oil injected or premixed two cycle engine made uses this form of lubrication. If it is good enough for the crank bearings why not for the counterbalancer. This is one of the reasons they use ball bearings and not flat babit bearings like in a car. They only need a very small oil film to lubricate them not pressurized oil like a car crankshaft.

 

[LouDoo]

Re: Posts 49, 50 and 51:

Wow, I've been on this forum for a few years and have owned and worked on SeaDoo's even longer. The topic of counterbalance lubrication has been bouncing around for a long time, with no definitive answers. This is by far the best explanation of how the counterbalance gets it's lubrication. It certainly has educated me, I'm thinking about combining these three posts and making a sticky in the two stroke section.

Any objections, additions?

Lou

 

[Seadoobuddy]

Lou, go for it. It can only help in the future to eliminate any confusing postings about it.
Then maybe close that thread that has the sticky.

 

[racerxxx]

4. Why the lounterbalancer oil seal? As we said in points 1 and 2 the counterbalancer is open to the crank and in a 2 stroke engine when the piston moves up it creates a vacuum in the crankcase that pulls the air and fuel mixture from the carbs into the crankcase and as it moves down this creates a positive pressure in the crankcase as the air/fuel is displaced by the piston forcing it up through the transfer ports that have been uncovered by the piston moving and into the combustion chamber, as the piston startes to move up it closes the transfer ports and startes to draw fresh air/fuel from the carbs into the crankcase hence 2 cycle engine. Agreed? This is a 2 cylinder engine and we have establshed that the counterbalancer is open to the MAG and PTO crankcase areas which brings us to the counterbalancer oil seal. Without this seal the counterbalancer cavity would act like a tube connecting the front and rear cylinders so when one was creating a low pressure and one was creating a high pressure as described above they would be fighting each other instead of drawing the air/fuel charge through the crankcase up into the combustion chamber. The mixture would be moving from front to rear instead of intake to exhaust.

The CB shaft has two seals back to back(actually face to face) on the PTO end. They are there to seal off the long cavity that would reach the front bearing. The front bearing is sealed, on both sides and is permenantly lubed. Once the case halves are put together and torqued you put the front MAG housing on. That housing is stepped to fit inside the case halves, and has a seal, to seal the end of the crankshaft. Between the case and housing there is a gasket that would seal off both the crank and the front CB bearing--there is NO transfer possible from the front to the back through the CB cavity. If you look at this pic you'll see the front of the 787, look at the machined surfaces, that is where the paper gasket will seal the two entities from each other. If you look at the second picture you'll see the mag housing gasket with the two open areas, the one where the crank seal is and the other square-ish hole is--this one is where the CB front bearing is. I don't think there could ever be a scavenging effect thru the CB cavity. I think the way the CB get's it lube can and has been discussed exponentially across many forums. I vote for leaving it as Black Magic is how it all works, some magician at BRP knows and if he tells anyone he'll have to kill us all.

 

[mikidymac]

Thanks RACERXXX I knew it coundn't transfer through the front where the MAG cover is. I was looking at the picture of the split cases you posted and didn't realize they were sitting front to back and back to front. I modified my explanation after reviewing your pictures and response. Hope that clears up the magic.

Now where is that dead horse? I'll get my beating stick.

 

[LouDoo]

So I'll take that as a no vote.

Lou

 

[racerxxx]

No problem. The cases in my first pics were not laid out on purpose for this thread.

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[IDoSeaDoo]

Well, regardless of your counterbalance beliefs, I think we can all agree that it is the lowest point in the motor, and that if we by chance forget to block off the water inlet hose upon being towed in, or otherwise fill the motor with water, it WILL accumulate in the CB shaft cavity. Hence, I've started drilling and tapping a fill and drain hole on all my new rebuilds. There are still a few TRUE hardware stores out there that sell pipe thread taps (for fill hole). For the drain, I have to take an allen bolt and custom cut it to length to make it fit perfectly in the outlet I tap. I will try to remember to post pics for you guys when I do my next engine here shortly.

 

[DA080682]

Let's beat the horse more....


Where does this port lead?

 

[racerxxx]

That is the fill hole for the early cases. If you grab an early manual, 96, you'll see them fill it through there

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[DA080682]

That is the fill hole for the early cases. If you grab an early manual, 96, you'll see them fill it through there

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So the base gasket and cylinder seal it off?

 

[racerxxx]

Nope but kinda, it's even in the later cases.

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[DA080682]

Nope but kinda, it's even in the later cases.

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So could this passage be used to drive fuel/oil flow through the CB gear passage and provide lubrication to the CB gears as well as the CB bearing and outboard crank bearings?