smoking from crank case breather separator? HELP - Honda Rebel Forum
 
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post #1 of 4 Old 07-13-2019, 10:56 PM Thread Starter
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smoking from crank case breather separator? HELP

I bought a 2002 nighthawk 250 a while back and rode it for about 150 miles with no issues.
out of nowhere the bike left me stranded so I got it towed home and discovered one of the alternator wires had sheered itself.
So I repaired the wire and it was running great again!
I decided to top off the oil since it was really low and now it's smoking like crazy! and running very strangely.
It started puking oil out the side and discovered that the crank seal had popped off after doing some reading.
I put it back in and then I noticed that the smokeisn't coming from the exhaust pipes, but rather from the center of the bike near that oil/breather/serpator thing.
I noticed that it seems like the serperator is coming apart, and it's oozing liquid.
I drained the puke tube and only a small amount of fluid came out.
Is this box supposed to be completely shut? I this thing able to be repaired? Should I order a new one?
Also, I noticed that If I leave the puke tube open the bike runs so good! but a ton of smoke/air comes out of the end.
It will also run really good if I leave the oil cap off, or if I remove the breather tube from the crank case.

I'm getting so frustrated and I don't know what to do . Should I bypass this little black box with a T? Or try fixing it?
I hope no damage was done since the oil level was low.

HELP.
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post #2 of 4 Old 07-13-2019, 11:32 PM
 
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The engine can NOT be over filled with oil! Over filling in the slightest amount will push out the crank seal, for sure. Take the dipstick out, wipe it clean and just drop it into the hole without screwing it in. Then take it out and get a reading. If it's over the high mark, it will push out the crank seal. In your case the oil separator sounds like it's absolutely saturated.

Try taking the separator apart and spraying it with brake wash. That will put it back to normal breathing, but since your bike is old, it may just need replaced.

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post #3 of 4 Old 07-13-2019, 11:38 PM
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Welcome to the forum. I'm going to make some assumptions here, namely that the Nighthawk and Rebel crankcase breather systems are similar.

You may have run too low on oil and the rings didn't get enough lubrication. Do a compression test. Pressure in each cylinder ought to be 150 psi or higher. There's a thread on how to do a compression test stickied in the Wrenching section of this forum.

The oil level is checked with the bike upright (not on the side stand), the dipstick unscrewed, and just resting on the threads. Is this how you measured it?

See this diagram for details https://www.cheapcycleparts.com/oemp...cb/air-cleaner

The separator has a bottom drain (puke tube) and is also connected to the air box. It's there to allow the crankcase to "breath" so it doesn't build up pressure and blow out that seal you reinstalled, collect crankcase condensate through the puke tube, and burn the remaining vapors by funneling them through the carb. If you remove the hose going to the separator, or leave the puke tube open, as the engine produces positive and negative pressure as the pistons move up and down, it will suck unfiltered air into the crankcase. That is not a good thing! Ditto for running the bike with the dipstick removed.

I recommend you either repair or replace whatever is defective with the crankcase ventilation system. Also suggest you gently run a wire up the puke tube to be sure there are no obstructions. I've seen some that weren't drained regularly develop a plug.

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post #4 of 4 Old 07-14-2019, 01:34 PM Thread Starter
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Quote:
Originally Posted by Guba View Post
The engine can NOT be over filled with oil! Over filling in the slightest amount will push out the crank seal, for sure. Take the dipstick out, wipe it clean and just drop it into the hole without screwing it in. Then take it out and get a reading. If it's over the high mark, it will push out the crank seal. In your case the oil separator sounds like it's absolutely saturated.

Try taking the separator apart and spraying it with brake wash. That will put it back to normal breathing, but since your bike is old, it may just need replaced.
Yes I know how to check the oil.
I’ll try removing the separator and seeing what’s up.

Quote:
Originally Posted by flitecontrol View Post
Welcome to the forum. I'm going to make some assumptions here, namely that the Nighthawk and Rebel crankcase breather systems are similar.

You may have run too low on oil and the rings didn't get enough lubrication. Do a compression test. Pressure in each cylinder ought to be 150 psi or higher. There's a thread on how to do a compression test stickied in the Wrenching section of this forum.

The oil level is checked with the bike upright (not on the side stand), the dipstick unscrewed, and just resting on the threads. Is this how you measured it?

See this diagram for details https://www.cheapcycleparts.com/oemp...cb/air-cleaner

The separator has a bottom drain (puke tube) and is also connected to the air box. It's there to allow the crankcase to "breath" so it doesn't build up pressure and blow out that seal you reinstalled, collect crankcase condensate through the puke tube, and burn the remaining vapors by funneling them through the carb. If you remove the hose going to the separator, or leave the puke tube open, as the engine produces positive and negative pressure as the pistons move up and down, it will suck unfiltered air into the crankcase. That is not a good thing! Ditto for running the bike with the dipstick removed.

I recommend you either repair or replace whatever is defective with the crankcase ventilation system. Also suggest you gently run a wire up the puke tube to be sure there are no obstructions. I've seen some that weren't drained regularly develop a plug.
One reason I don’t think the rings are bad is because the bike runs really well and there’s ZERO smoke coming out the exhaust. And yes. I know how to check the oil. I’m going to remove the separator and check it out. I know the rebel separator has 4 hold down screws and the nighthawk has 2.
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