1996 787 countershaft leaking oil

[Deepcove1]

I have a 1996 Challenger with the 787. I rebuilt the top end, added fresh carbs and fired it up.
It will not run except on very rough idle. I noticed a lot of black oil discharge in the exhaust.
This appears to be the 30W oil from the countershaft. I removed the oil filler cap for the counterbalance fill hole, and jammed a hose tightly into it. When I blow into the hose, I hear the air leaking thru to the PTO carb, so obviously the 30W oil will drain into the PTO crankcase.
Does this imply that the seal on the crankshaft next to the PTO side gear is the culprit? There is a seal on the counterbalance shaft as well, but there doesn't appear to any connection otherwise into the crankcase that way.
How difficult is this fix?

 

[Dr Honda]

2-strokes build oil in the exhaust... and it will blow out. And, it will be black, because it will be full of carbon from the exhaust. So... you can't assume that it's the oil from the gears.

Some engine cases have an internal hole... so you can't assume that the air you are blowing is a bad thing.


Unfortunately... if you think the oil has come out... all you can do, is strip the engine down, and check it.

 

[Deepcove1]

Thanks for the quick response. I started this thread because I spent a couple hours last nite trying to get a good idea of the details of the circuitry and seals around the gears that drive the counterbalance shaft. There certainly are a lot of opinions out there and the truth is that I didn't find the answer I wanted. In my case the entire exhaust system had been flushed out, so the oil discharge I'm seeing is new.
The question is, if in actual fact that I have a seal problem, could it be the seal on the counterbalance, or is it the labryith seal on the crankshaft. Long shot, is maybe I only have some type of bottom end sealing problem. Engine is out, I just dread that bottom end work, shouldn't have short-cut the job on the top end before I re-installed it! I have actually been running the engine quite a bit without the pump installed and with a direct water supply to try to see if it would settle down if it blew all the oil out, but it didn't change, bogs down on rev up.

 

[Guest_User]

could it be the seals for the rotary valve leaking oil from the tank into the engine?

 

[Deepcove1]

That is a separate compartment in the middle of the crankshaft that drives the rotary valve. I did a pressure test on it and it was ok and that is a different oil type as well...The compartment that drives the counterbalance shaft is by the PTO side....Thanks.

 

[kicker]

Unless 787's in boats are different then skis, I cant see that 30w oil making it through the exhaust system and look like excessive oil coming out, there is only 1oz (30ml) of oil in that cavity. Not enough to make it look like an oil leak IMO. Most of it would get burned up while the engine was running.

I am also a little confused as to the "cap for the counterbalance", because pre 97's did not have a refillable cavity or drain, there is a hole in the bottom of the cavity where the fuel oil mixture gets in to lube the gear. It was filled at assembly for initial start up and left alone until the next rebuild. Now of course it is possible that someone installed a fill plug and drain at one point.

Heres a counterbalance thread, it has a picture of the hole the Doc was referring to post #59
http://www.seadooforum.com/showthread.php?58455-counterbalance-oil-type

 

[Deepcove1]

I don't know the full history of the beast, it was a $500 winter project that I dragged out of the bush. Everything was disassembled, the engine was in boxes. Perhaps the engine is newer than 96, but yes, it does have that oil filler cap of the newer ones. I would run out to the garage and get the serial number to try to look it up, but I'm on the Oregon coast right now, "enjoying the rain". Just like being at home on the Canadian "wet coast". Back to the project next week. BTW the 96 manual shows the engines having this oil cap, but then those photos may just be generics of the 787. Perhaps the crank case has been full of oil from the previous abuser......stand-by for solution...